# Patent

## Title
Host based satellite positioning systems

## Abstract

Methods and systems consistent with the present invention provide a host based positioning system. The host based positioning system includes a tracker hardware interface that connects to a dedicated hardware space vehicle tracker. The tracker hardware interface receives positioning information from the space vehicle tracker. The host based positioning system also includes a memory that includes a GPS library having a user interface, a tracker interface, and an operating system interface. A processor runs functions provided by the interfaces.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser. No. 11/149,438, entitled HOST BASED SATELLITE POSITIONING SYSTEMS, filed Jun. 6, 2005 which is a continuation of U.S. patent application Ser. No. 10/269,914, entitled HOST BASED SATELLITE POSITIONING SYSTEMS, filed on Oct. 10, 2002, that issued as U.S. Pat. No. 7,043,363 on May 9, 2006, which was related to U.S. patent application Ser. No. 10/269,105, titled, “LAYERED HOST BASED SATELLITE POSITIONING SOLUTIONS”, filed on Oct. 10, 2002, and U.S. patent application Ser. No. 10/269,104, titled, “NAVIGATION PROCESSING IN HOST BASED SATELLITE POSITIONING SOLUTIONS”, filed Oct. 10, 2002, both of which were incorporated by reference in their entirety and which are also incorporated by reference herein.


BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to satellite positioning systems. In particular, this invention relates to satellite positioning systems implemented utilizing the processing power of a host in communication with a hardware tracker.
2. Related Art
The worldwide utilization of wireless devices such as two-way radios, pagers, portable televisions, personal communication system (“PCS”), personal digital assistants (“PDAs”) cellular telephones (also known a “mobile phones”), Bluetooth, satellite radio receivers and Satellite Positioning Systems (“SPS”) such as Global Positioning Systems (“GPS”), also known as NAVSTAR, is growing at a rapid pace. Current trends are calling for the incorporation of SPS services into a broad range of electronic devices and systems, including Personal Digital Assistants (PDAs), cellular telephones, portable computers, automobiles, and the like. At the same time, manufacturers constantly strive to reduce costs and produce the most cost-attractive product possible for consumers.
In the past, providing a SPS solution often involved expensive dedicated SPS signal reception and processing hardware, as well as dedicated post processing hardware for resolving location measurements, displaying location coordinates, updating map displays, and the like. However, given the rapid growth in speed, sophistication, and processing power of the host microprocessors present in the host device (e.g., in a cellular telephone or automobile), the possibility exists for allowing the host microprocessor to bear the burden not only of running its regular applications, but also to operate as part of the SPS solution. Such an approach is presented in U.S. Pat. No. 6,430,503, titled “Distributed GPS Navigation System,” issued to Paul W. McBurney et al., the entirety of which is incorporated herein by reference.
As noted above, however, there is a strong push toward incorporating SPS solutions in many electronic devices designed by numerous manufacturers. Of course, each device varies considerably in architecture, operating system, hardware interfaces, and the like. Prior SPS solutions did not provide the flexibility that allowed the solutions to be adapted to a wide range of electronic devices. Instead, expensive customized solutions were needed for each device, thereby undesirably increasing costs and delaying the introduction of SPS services into a wide range of devices.
Therefore, a need exists for implementations of SPS solutions that overcome the problems noted above and others previously experienced.
SUMMARY
Methods and systems consistent with an invention of a host based SPS solution are disclosed. The SPS solution is implemented in a convenient library form that is flexible and extensible, and that may adapt to meet he needs of many different hardware platforms. As a result, a wide variety of electronic devices may incorporate SPS functionality with less expense utilizing less development time.
In one example implementation, a host based SPS system may include a host processing system that connects through a tracker hardware interface to a dedicated hardware space vehicle tracker. The host processing system may also include a memory that includes a SPS library having a user interface, positioning engine, a tracker interface and an operating system interface. A processor in the host processing system runs the positioning engine and the functions provided by the interfaces.
The tracker hardware interface receives positioning information from the space vehicle tracker. Through functions in the tracker interface, the positioning information is communicated to the positioning engine. In turn, the positioning engine may determine a position and communicate the position to a user application through functions provided in the user interface.
Other apparatus, systems, methods, features and advantages of the present invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.



BRIEF DESCRIPTION OF THE FIGURES
The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views.
FIG. 1 illustrates a detailed block diagram of one example of a positioning systems implemented as a host based SPS solution.
FIG. 2 illustrates a hardware tracker that communicates with the positioning system shown in FIG. 1.
FIG. 3 depicts a hardware and software diagram of a positioning system that includes a GPS library with a user interface, a tracker interface, and an operating system interface.
FIG. 4 illustrates a flow diagram of a user program running in the positioning system.
FIG. 5 illustrates a block diagram of the cooperation between threads, tasks and hardware in one implementation of a host based SPS solution.
FIG. 6 illustrates an execution schedule for a receive manager thread and a periodic navigation task.
FIG. 7 illustrates a synchronization diagram for the timing and interaction between the threads and tasks shown in FIG. 5.



DETAILED DESCRIPTION
Reference will now be made in detail to an implementation in accordance with methods, systems, and products consistent with the present invention as illustrated in the accompanying drawings. The same reference numbers may be used throughout the drawings and the following description to refer to the same or like parts.
A typical satellite positioning system (“SPS”) system has approximately 12 satellites that may be visible at any one time to a wireless device. SPS means any system utilizing satellites and/or land-based communications devices for providing or enabling the determination of a location of the wireless device on the earth, for example but not limited to: the global positioning system (“GPS”) known as NAVSTAR, GLONASS, LORAN, Shoran, Decca, or TACAN. Although many of the interface functions below make reference to GPS, those functions are not limited to use with GPS, but, generally, are equally applicable in other SPS environments.
FIG. 1 depicts a block diagram of a positioning system 100 suitable for practicing methods and implementing systems consistent with the present invention. The positioning system 100 includes a host 102 and tracker hardware 104. The host 102 includes a central processing unit (“CPU”) 106, a hardware tracker interface 110, and a memory 112. The host 102 also includes a secondary storage device 114 (e.g., generally non-volatile memory such as a magnetic disk, flash memory, optical storage, and the like), and a display 116, and an input interface 118 (e.g., a mouse, keyboard, and the like).
An operating system 120 (e.g., Windows CE, QNX, Palm OS, UNIX, Linux, Windows 2000, NT, XP, or the like) runs in the memory 112. As will be explained in more detail below, a user program 122 communicates with a SPS library 124 and the operating system 120. The user program 122 thereby receives position information from the GPS library, and may also communicate commands to the SPS library. The user program 122 may be any program that utilizes positioning information, including, as examples, a mapping program, course charter, location aid, and the like.
The host 102 connects through the hardware tracker interface 110 and the interface connection 126 to the tracker hardware 104. The hardware tracker interface 110 may be virtually any type of data transfer interface (as examples, a serial, parallel, compact flash, PC Card, or network interface). The interface connection 126 may then be, as examples, a serial cable, parallel cable, or network cable, and may optionally be wireless. In one implementation, the hardware tracker interface 110 is an RS232 port running at 38,400 bps, N-8-1 that communicates up to 2 KB of data per second between the host 102 and the tracker hardware 104.
In other implementations, the tracker hardware (as illustrated by the reference numeral 128) is more closely incorporated into the host 102. Thus, rather than connecting to the host 102 through the interface connection 126, for example, the tracker hardware 128 may be directly coupled to the host 102 address, data, and control buses. As will be explained in more detail below, the host 102 receives and processes navigation information from the hardware tracker 104, 128 in order to provide the user programs 122 with position information.
Although aspects of the present invention are depicted as being stored in memory 112, one skilled in the art will appreciate that all or part of systems and methods consistent with the present invention may be stored on or read from other machine-readable media, for example, secondary storage devices such as hard disks, floppy disks, and CD-ROMs; a signal received from a network; or other forms of ROM or RAM either currently known or later developed. Further, although specific components of positioning system 100 are described, one skilled in the art will appreciate that a positioning system suitable for use with methods, systems, and articles of manufacture consistent with the present invention may contain additional or different components. For example, the CPU 106 may be a microprocessor, microcontroller, application specific integrated circuit (“ASIC”), discrete or a combination of other types of circuits acting as a central processing unit. The memory 112 may be RAM, DRAM, SDRAM, or any other type of read/writeable memory.
Turning next to FIG. 2, that figure shows one example of an implementation of the tracker hardware 104. The tracker hardware 104 acquires and tracks SPS satellites and sends raw measurement data to the host 102 for position calculation. To that end, the tracker hardware 104 includes an antenna 202 for receiving SPS satellite signals and a radio frequency (“RF”) filter 204 for passing the signals to the RF interface circuit 206. The RF interface circuit 206 processes the signals, produces 2-bit Inphase and Quadrature (“I/Q”) signals and recovers SPS clocks. The RF interface circuit 206 provides the I/Q signals and SPS clocks to the location processing circuit 208 for digital processing. A reference frequency source 210 (e.g., a crystal oscillator) provides a reference clock for the RF interface circuit 206, while the optional real time clock (“RTC”) source 212 provides a reference clock for the location processing circuit 208.
The tracker hardware 104 may be implemented with components available from SiRF Technology, Inc. of San Jose Calif. For example, the RF interface circuit 206 may be implemented as a GRF2i/LP integrated circuit. The location processing circuit may be implemented, as examples, as a GSP2t integrated circuit or GSP2e integrated circuit. The tracker hardware 104 minimizes the overhead on the host 102 and operating system 120 by keeping low the maximum transmission rate of raw measurements to the host 102 (e.g., one measurement per second).
With regard next to FIG. 3, that figure shows a detailed block diagram of a hardware and software diagram 300 for the positioning system 100. The memory 112 in the host 102 includes a SPS library 124, user programs 122 (e.g., map displaying, map matching, dead reckoning and route calculation programs), and the operating system 120 (which may be a multi-threaded operating system). The SPS library 124 includes a positioning engine 302, a user interface 304, a tracker interface 306, and an operating system interface 308. The user tasks 310 implement device drivers or link directly to the user programs 122, as examples.
In addition to the hardware tracker 104, persistent storage 312 and a real time clock 314 may optionally be provided. The persistent storage 312 may be, as examples, 2 KB of Flash memory, battery backed up RAM or a disk drive. The SPS library 124 may use the RTC in the host 102, the RTC 314, or may operate without an RTC.
The user interface 304 is called by the user programs 122 to start and configure the positioning system. The positioning engine 302 calls a function provide by the user program 122 (e.g., GPS_Output) to deliver positioning messages (e.g., position updates and other synchronous and asynchronous data) to the user program 122. The tracker interface 306′ provides for communication between the tracker hardware 104 and the host 102 and, to that end, may load and call the operating system 120 serial communication drivers. The operating system interface 308 calls operating system functions for task scheduling and synchronization, RTC access, and storage access.
FIG. 4 shows a flow diagram of a user program 122. The user program 122 calls GPS_Start to start the positioning engine 302 (step 402). The user program 122 determines whether to configure the positioning engine 302 (step 404). The program 122 configures the positioning engine 302 by sending a message to the positioning engine 302 using the GPS_Input function, for example (step 406). Next, the program 122 waits for a new position fix (or other information) from the positioning engine 302 (step 408).
When information is received, the user program 122 processes the information, for example, to display or update a map (step 410). If the program 122 continues to run (step 412), processing returns to step 404. Otherwise, the program 122 stops the positioning engine (step 414) and terminates. The positioning engine runs separately and, when new positioning information is available, creates a message for the program 122 (step 416) and sends the message to the program 122 (step 418). Tables 1-5 below show exemplary function calls.







TABLE 1





GPS_Start( )















/* Starts GPS Engine tasks, initial acquisition begins: */


tGPS_UINT32        result;


result = GPS_Start (








       GPS_CTRL_MODE_AUTO,
  /* default - hot start */


       0,
/* use default clock offset */


       1,
/* use port 1 */


       38400
/* baud rate */


      );
















TABLE 2





User Callback GPS_Output( )

















/* User callback function. Receives all communication from GPS. */



#include “GPS_interface.h”



void GPS_Output(



  tGPS_UINT32 message_id,



  void *    message_structure,



  tGPS_UINT32  length )



{



  tGPS_NAV_MEASURED_NAVIGATION nav_data;



  switch ( message_id )



 {



    case GPS_NAV_MEASURED_NAVIGATION:



     memcpy( &nav_data, message_structure,



sizeof(tGPS_NAV_MEASURED_NAVIGATION) );



    if ( nav_data.nav_mode & GPS_MODE_MASK )



     {



     printf(“x=%ld, y=%ld, z=%ld \n”,



        nav_data.ecef_x, nav_data.ecef_y, nav_data.ecef_z);



     else



       printf(“no fix \n”);



     break;



    case GPS_NAV_MEASURED_TRACKER:



     /*...*/



     break;



    default:



     /*...*/



     break;



  } // switch



} // GPS_Output( )
















TABLE 3





Configure using GPS_Input( )

















/* Configures GPS Engine to turn off SBAS correction: */



 tGPS_NAV_SET_DGPS_SOURCE  DGPSSrc;



 tGPS_UINT32        result;



 DGPSSrc.bit_rate = 0;



 DGPSSrc.freq = 0;



 DGPSSrc.src = GPS_DGPS_SRC_NONE;



 result = GPS_Input( GPS_NAV_SET_DGPS_SOURCE,



 (void*)&DGPSSrc,



sizeof(DGPSSrc) );
















TABLE 4





Configure using GPS_Input( )















 /* Forces cold start of GPS receiver: */


 tGPS_NAV_INITIALIZE      InitMsg;


 tGPS_UINT32        result;


 memset(&InitMsg, 0, sizeof(InitMsg));


InitMsg.restart_flags = GPS_RESTART_COLD;


 result = GPS_Input (  GPS_NAV_INITIALIZE, (void*)&InitMsg,


 sizeof(InitMsg) );
















TABLE 5





GPS_Stop( )


















/* Stops GPS Engine and all SiRFNav tasks: */




tGPS_UINT32        result;




result = GPS_Stop( );









Below, one exemplary implementation of the user interface 304, tracker interface 306, and an operating system interface 308 is set forth. Table 6 shows which functions and messages are associated with each interface, while Tables 7-10 set forth files and data types used or referred to in the follow description.







TABLE 6





Interface Functions and Messages

















User Interface:



GPS_Start( )



GPS_Stop( )



GPS_Output( )



GPS_Input( )



GPS_NAV_MEASURED_NAVIGATION output message



GPS_NAV_MEASURED_TRACKER output message



GPS_NAV_SW_VERSION output message



GPS_NAV_CLOCK_STATUS output message



GPS_NAV_ERROR output message



GPS_ADC_ODOMETER_DATA output message



GPS_NAV_COMPLETE output message



GPS_NAV_TEXT output message



GPS_NAV_INITIALIZE input message



GPS_NAV_POLL_SW_VERSION input message



GPS_NAV_SET_DGPS_SOURCE input message



GPS_NAV_POLL_CLOCK_STATUS input message



GPS_NAV_SET_SBAS_PRN input message



Operating system interface:



OS_Thread_Create( )



OS_Thread_Delete( )



OS_Thread_Sleep( )



OS_Mutex_Create( )



OS_Mutex_Delete( )



OS_Mutex_Enter( )



OS_Mutex_Exit( )



OS_Semaphore_Create( )



OS_Semaphore_Delete( )



OS_Semaphore_Wait( )



OS_Semaphore_Release( )



OS_Storage_Open( )



OS_Storage_Close( )



OS_Storage_Write( )



OS_Storage_WriteAll( )



OS_Storage_Read( )



OS_RTC_Read( )



Tracker interface:



GPS_COMM_TRK_Create( )



GPS_COMM_TRK_Delete( )



GPS_COMM_TRK_Open( )



GPS_COMM_TRK_Reopen( )



GPS_COMM_TRK_Close( )



GPS_COMM_TRK_Wait( )



GPS_COMM_TRK_Read( )



GPS_COMM_TRK_Write( )

















TABLE 7





Include file
Description







gps_types.h
Type definitions used in GPS library interfaces


gps_rtos.h
Definitions and prototypes of the GPS



operating system interface


gps_ctrl.h
Definitions and prototypes of the GPS control



interface


gps_interface.h
Definitions and prototypes of the GPS



communication interface


gps_messages.h
Definitions and structure defines of messages



used by the communication interface


gps_comm_trk.h
Definitions and prototypes of the tracker



communication interface


gps_proto_sirfbinary.h
Definitions and prototypes of the binary serial



protocol


gps_debug.h
Definitions for development and debugging

















TABLE 8





Source file
Description







gps_rtos.c
Contains implementation of the GPS operating system



interface


gps_comm_trk.c
Contains implementation of the tracker communication



interface



















TABLE 9







Library file
Description









SiRFNavServer.lib
GPS receiver library

















TABLE 10







Data Types









Type name
Data range
Defined as





tGPS_SINT8
−128 . . . 127
signed char


tGPS_UINT8
0 . . . 255
unsigned char


tGPS_SINT16
−32768 . . . 32767
signed short


tGPS_UINT16
0 . . . 65535
unsigned short


tGPS_SINT32
−2147483648 . . . 2147483647
signed long


tGPS_UINT32
0 . . . 4294967295
unsigned long


tGPS_HANDLE
32 bit pointer
void *









The user or GPS interface includes a GPS control interface and a GPS communication interface. The GPS control Interface functions allow a user program to start and stop the GPS engine using the functions shown in Table 11.











TABLE 11







Function
Description
Provided in









GPS_Start( )
Starts GPS engine
GPS library



GPS_Stop( )
Stops GPS engine
GPS library










The GPS communication interface functions allow a user program to send and receive messages to and from the GPS engine using the functions shown in Table 12.









TABLE 12





Function
Description
Provided in







GPS_Output( )
Receives a data from the GPS engine
user code


GPS_Input( )
Send commands to the GPS engine
GPS library









GPS_Start( ) initializes and starts positioning engine threads and communication interface. This function should be called by user programs to start GPS activity.








TABLE 13








Include file



  gps_ctrl.h



Syntax



  tGPS_RESULT GPS_Start(tGPS_UINT32 start_mode,



      tGPS_UINT32 clock_offset,



      tGPS_UINT32 port_num,



      tGPS_UINT32 baud_rate )













Parameter
Data range
Units
Description





start_mode


Start configuration flags.





See Table 14below for





details.


clock_offset
0, 25000 . . . 146000
Hz
Default GPS clock offset.





This value is used by the





factory start or when a





saved value is not available.





This value should reflect a





tracker's hardware





peculiarity. If zero is





provided here a default





value of 96250 Hz is used.


port_num
1 . . . 64

Specifies a





communication port where





tracker is connected to.





1 = serial port 1, 2 = serial





port 2, . . .


baud_rate
4800, 38400, 57600,
bps
Specifies a baud rate at



115200

which tracker is connected





to. Default 2t tracker baud





rate is 38400 bps.































TABLE 14







31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16










Reserved. Write 0 only.

























15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0













Text
ADC
Reserved. Write 0 only.
Start type. See


enable
mode.

below for allowed



See

values.



below.
















TABLE 15







Text Enable









Value
Macro
Description





0

Development text




messages are disabled




after start. Can be




enabled later by GPS




input message.


1
GPS_CTRL_MODE_TEXT_ENABLE
Enables development




text messages right




after start




(via GPS_Output( )




function)
















TABLE 16







ADC Mode









Value
Macro
Description





0

ADC messages from tracker are disabled.


1
GPS_CTRL_MODE_ADC_ENABLE_1HZ
Enables ADC message from tracker at




1 Hz rate


2
GPS_CTRL_MODE_ADC_ENABLE_10HZ
Enables ADC message from tracker at




10 Hz rate


3

Reserved
















TABLE 17







Start Type









Value
Macro
Description





0
GPS_CTRL_MODE_AUTO
GPS will automatically choose a




start mode accordingly to




availability of time, position and




ephemeris information. This




start mode should be used for




normal operation.


1
GPS_CTRL_MODE_HOT
For testing purposes only. GPS




will make a hot start.


2
GPS_CTRL_MODE_WARM
For testing purposes only. GPS




will make a warm start.


3
GPS_CTRL_MODE_COLD
For testing purposes only. GPS




will make a cold start.


4
GPS_CTRL_MODE_FACTORY
For testing purposes only. GPS




will make a factory cold start. 




All saved information will be




deleted.


5
GPS_CTRL_MODE_TEST
For SiRF internal testing




purposes only.


Other

Reserved


value
















TABLE 18







Return Values








Return value
Description





GPS_SUCCESS
GPS engine has started



successfully


GPS_CTRL_ALREADY_STARTED
Error: GPS engine is already



running


GPS_CTRL_INVALID_MODE
Error: invalid start mode


GPS_CTRL_CLOCK_OFFSET_OUT_OF_RANGE
Error: clock offset is out of range


GPS_CTRL_ERROR_OPENING_PORT
Error: could not open serial port


GPS_CTRL_RTOS_ERROR
Error creating OS objects (threads,



semaphores, mutexes)
















TABLE 19





Example

















#include “gps_types.h”



#include “gps_ctrl.h”



if ( GPS_Start(GPS_CTRL_MODE_AUTO |



GPS_CTRL_MODE_TEXT_ENABLE, 



96250, 1, 38400) != GPS_SUCCESS )



{



  // error handler



}



// GPS engine has started successfully



...









The GPS_Stop function stops the positioning engine threads and communication interface. This function should be called by the user program to stop GPS activity.














Include file



gps_ctrl.h



Syntax



tGPS_RESULT GPS_Stop( void )











Return value
Description





GPS_SUCCESS
GPS engine has stopped



successfully


GPS_CTRL_ALREADY_STOPPED
Error: GPS engine is already



stopped
















TABLE 21





Example

















#include “gps_types.h”



#include “gps_ctrl.h”



if ( GPS_Stop( ) != GPS_SUCCESS )



{



   // error handler



}



// GPS engine has stopped successfully



...









The GPS_Output function retrieves a message from positioning engine. There are no return values. The function is called by the positioning engine whenever any message is sent out. This function is implemented by the user program and statically linked with the GPS library.








TABLE 22








Syntax



void GPS_Output( tGPS_UINT32 message_id, void *message_structure,



tGPS_UINT32 length )













Parameter
Data range
Units
Description





message_id
GPS_NAV_MEASURED_NAVIGATION

Message



GPS_NAV_MEASURED_TRACKER

identifier. See



GPS_NAV_RAW_TRACKER

chapter 7 for



GPS_NAV_SW_VERSION

message



GPS_NAV_CLOCK_STATUS

details.



GPS_NAV_50BPS_DATA





GPS_NAV_ERROR





GPS_NAV_ACK





GPS_NAV_NAK





GPS_NAV_VISIBLITY_LIST





GPS_NAV_NL_MEAS_DATA





GPS_NAV_NL_DGPS_DATA





GPS_NAV_NL_SV_STATE_DATA





GPS_NAV_NL_INIT_DATA





GPS_ADC_ODOMETER_DATA





GPS_NAV_COMPLETE





GPS_NAV_TEXT




message_structure
32 bit pointer

Pointer to the





message





structure with





data


Length
Varies depending on the message
bytes
Length of the





message





structure
















TABLE 23





Example

















#include “gps_types.h”



#include “gps_interface.h”



#include “gps_messages.h”



void GPS_Output( tGPS_UINT32 message_id,



void *message_structure, tGPS_UINT32 length )



{



  tGPS_NAV_MEASURED_NAVIGATION nav_data;



  switch ( message_id )



  {



    case GPS_NAV_MEASURED_NAVIGATION:



      memcpy( &nav_data, message_structure,



sizeof(tGPS_NAV_MEASURED_NAVIGATION) );



      if ( nav_data.nav_mode & GPS_MODE_MASK )



        printf(“x=%ld, y=%ld, z=%ld \n”,



        nav_data.ecef_x, nav_data.ecef_y,



        nav_data.ecef_z);



      else



        printf(“no fix \n”);



      break;



    case GPS_NAV_MEASURED_TRACKER:



      // use tracker information here



      break;



  default:



      break;



  } // switch



} // GPS_Output( )









The GPS_Input function sends a command to the GPS engine. The function may be called by the client program to send a command to the GPS receiver.








TABLE 24








Include file



gps_interface.h



Syntax



tGPS_UINT32 GPS_Input( tGPS_UINT32 message_id, void *message_structure,



tGPS_UINT32 length )













Parameter
Data range
Units
Description





message_id
GPS_NAV_INITIALIZE

Message identifier.



GPS_NAV_POLL_SW_VERSION

See chapter 7 for



GPS_NAV_SET_DGPS_SOURCE

message details.



GPS_NAV_SET_NAV_MODE





GPS_NAV_SET_DOP_MODE





GPS_NAV_SET_DGPS_MODE





GPS_NAV_SET_ELEV_MASK





GPS_NAV_SET_POWER_MASK





GPS_NAV_SET_STAT_NAV





GPS_NAV_POLL_CLOCK_STATUS





GPS_NAV_POLL_RX_MGR_PARAMS





GPS_NAV_SET_MSG_RATE





GPS_NAV_SET_SBAS_PRN




message_structure
32 bit pointer

Pointer to the





message structure





with data to send


length
Varies depending on the message
bytes
Length of the





message structure
















TABLE 25







Return values








Return value
Description





GPS_SUCCESS
Message was sent successfully


GPS_ERROR
Error: Message was not



acknowledged


GPS_ERROR_NOT_STARTED
Error: GPS engine is not running
















TABLE 26





Example

















#include “gps_types.h”



#include “gps_interface.h”



#include “gps_messages.h”



/* Forces cold start of GPS receiver: */










tGPS_NAV_INITIALIZE
InitMsg;



tGPS_UINT32
result;









memset( &InitMsg, 0, sizeof(tGPS_NAV_INITIALIZE) );



InitMsg.restart_flags = GPS_RESTART_COLD;



result = GPS_Input( GPS_NAV_INITIALIZE, (void*)&InitMsg,



sizeof(tGPS_NAV_INITIALIZE) );









The GPS communication interface messages are exchanged between the GPS client (e.g., a user program) and positioning or GPS engine via the user interface input and output functions.







TABLE 27







Primary GPS output messages









Message id




value
Message id macro
Description













2 
(0x02)
GPS_NAV_MEASURED_NAVIGATION
Provides ECEF position, velocity,





GPS time, position status


4 
(0x04)
GPS_NAV_MEASURED_TRACKER
Provides satellite status, azimuth,





elevation and C/No information


6 
(0x06)
GPS_NAV_SW_VERSION
Provides GPS engine software 





version


7 
(0x07)
GPS_NAV_CLOCK_STATUS
Provides current GPS clock status


10 
(0x0A)
GPS_NAV_ERROR
Provides error information


45 
(0x2D)
GPS_ADC_ODOMETER_DATA
Provides ADC, odometer and GPIO





values from tracker


47 
(0x2F)
GPS_NAV_COMPLETE
This message is sent as a last one in





the navigation cycle. Informs that





navigation cycle is complete.


255 
(0xFF)
GPS_NAV_TEXT
Provides development text





information
















TABLE 28







Primary GPS input messages









Message id




value
Message id macro
Description













128 
(0x80)
GPS_NAV_INITIALIZE
Performs re-





initialization of the





GPS receiver:





factory, cold, warm





or hot restarts.


132 
(0x84)
GPS_NAV_POLL_SW_VERSION
Asks for the GPS





engine software





version


133 
(0x85)
GPS_NAV_SET_DGPS_SOURCE
Sets differential





correction source


144 
(0x90)
GPS_NAV_POLL_CLOCK_STATUS
Asks for the current





GPS clock status


170 
(0xAA)
GPS_NAV_SET_SBAS_PRN
Sets SBAS





(WAAS/EGNOS)





PRN number
















TABLE 29







Additional GPS output messages for development and debug process









Message id




value
Message id macro
Description













8 
(0x08)
GPS_NAV_50BPS_DATA
Provides 50 bps





subframe data


11 
(0x0B)
GPS_NAV_ACK
Command





acknowledgment


12 
(0x0C)
GPS_NAV_NAK
Command not





acknowledgment


13 
(0x0D)
GPS_NAV_VISIBLITY_LIST
Provides current





visibilty list


28 
(0x1C)
GPS_NAV_NL_MEAS_DATA
Provides navigation





library measurement





data


29 
(0x1D)
GPS_NAV_NL_DGPS_DATA
Provides navigation





library differential data


30 
(0x1E)
GPS_NAV_NL_SV_STATE_DATA
Provides navigation





library satellite state





data


31 
(0x1F)
GPS_NAV_NL_INIT_DATA
Provides navigation





library initialization





data
















TABLE 30







Additional GPS input messages for development and debug process









Message id




value
Message id macro
Description













136 
(0x88)
GPS_NAV_SET_NAV_MODE
Sets navigation mode


137 
(0x89)
GPS_NAV_SET_DOP_MODE
Sets DOP mask control mode


138 
(0x8A)
GPS_NAV_SET_DGPS_MODE
Sets differential mode of operation


139 
(0x8B)
GPS_NAV_SET_ELEV_MASK
Sets elevation mask


140 
(0x8C)
GPS_NAV_SET_POWER_MASK
Sets power mask


143 
(0x8F)
GPS_NAV_SET_STAT_NAV
Configures static navigation mode


152 
(0x98)
GPS_NAV_POLL_RX_MGR_PARAMS
Asks for current navigation parameters


166 
(0xA6)
GPS_NAV_SET_MSG_RATE
Sets message output rate









The GPS_NAV_MEASURED_NAVIGATION output message provides ECEF position, velocity, GPS time and position status information. The message is outputted periodically at 1 Hz rate:








TABLE 31








  Include file



  gps_messages.h



Message id:













Value
Macro






2 (0x02)
GPS_NAV_MEASURED_NAVIGATION
















TABLE 32







Message structure


tGPS_NAV_MEASURED_NAVIGATION














Data range





Structure

(after de-
Scale




member
Data type
scaling)
factor
Units
Description















ecef_x
SINT32

1
meters
Computed ECEF


ecef_y
SINT32

1
meters
position.


ecef_z
SINT32

1
meters



ecef_vel_x
SINT16

0.125
m/sec
Computed ECEF


ecef_vel_y
SINT16

0.125
m/sec
velocity


ecef_vel_z
SINT16

0.125
m/sec



nav_mode
UINT8

n/a
n/a
Navigation status







flags. See below for







details.


hdop
UINT8
0 . . . 50.0
0.2
n/a
Horizontal Dilution







Of Precision


nav_mode2
UINT8

n/a
n/a
Navigation status







flags. See below for







details.


gps_week
UINT16
>0
1
n/a
Computed full GPS







week number.


gps_tow
UINT32
0 . . . 604799.99
0.01
sec.
Computed GPS time







of the week.


sv_used_cnt
UINT8
0 . . . 12
1
n/a
Number of satellites







used in solution.


sv_used
UINT8[12]
1 . . . 32
1
n/a
Array of PRN







numbers of satellites







used in solution





Note:


To get a real value of the parameter a value from the structure should be multiplied by the scale factor.













TABLE 33







nav_mode bit fields














7
6
5
4
3
2
1
0














DGPS
DOP
Altitude status
reserved 0
Position status


status
mask






status
















TABLE 34







Position status









Value
Macro
Description





0

No navigation solution


1

1 satellite degraded solution


2

2 satellites degraded solution


3

3 satellites solution (2D)


4

More than 3 satellites solution (3D)


5

3 satellites least square solution (2D)


6

More than 3 satellites least square




solution (3D)


7

Dead reckoning
















TABLE 35







Altitude status









Value
Macro
Description





0

No altitude hold


1

Altitude used from filter


2

Altitude used from user


3

Forced altitude (from user)
















TABLE 36







DOP mask status:









Value
Macro
Description





0

DOP mask not




exceeded


1
GPS_MODE_DOP_MASK_EXCEED
DOP mask exceeded
















TABLE 37







DGPS status:









Value
Macro
Description





0

Differential corrections are not




used in solution


1
GPS_MODE_DGPS_USED
Differential corrections are used in




solution
















TABLE 38







nav_mode2 bit fields:














7
6
5
4
3
2
1
0





reserved
reserved
reserved
reserved
reserved
DR timed
Solution
reserved







out
validation status
















TABLE 39







Solution validation status:









Value
Macro
Description





0

Solution is not




validated


1
GPS_MODE2_SOLUTION_VALIDATED
Solution is validated
















TABLE 40







DR timed out status:









Value
Macro
Description





0

Dead reckoning not timed




out


1
GPS_MODE2_DR_TIMED_OUT
Dead reckoning has timed




out









The GPS_NAV_MEASURED_TRACKER output message provides satellite status, azimuth, elevation and C/No information. The message is outputted periodically at 1 Hz rate.









TABLE 41









  Include file



  gps_messages.h



Message id:














Value
Macro







4 (0x04)
GPS_NAV_MEASURED_TRACKER

















TABLE 42





Message Structure

















Message structure



tGPS_NAV_MEASURED_TRACKER

















Data range





Structure

(after de-
Scale




member
Data type
scaling)
factor
Units
Description





gps_week
UINT16
1 . . .
1

Computed full GPS week







number.


gps_tow
UINT32
0 . . . 604799.99
0.01
sec.
Computed GPS time of







the week.


chnl_cnt
UINT8
12
1

Number of receiver's







channels


chnl
tGPS_SV_INFO[12]



Array of structures







containing satellite







information for each







receiver channel. See







below.
















TABLE 43







tGPS_SV_INFO sub-structure:














Data range





Structure

(after de-
Scale




member
Data type
scaling)
factor
Units
Description















svid
UINT8
1 . . . 32
1

Satellite PRN number


azimuth
UINT8
0 . . . 359.5
1.5
deg.
Satellite azimuth angle.


elevation
UINT8
0 . . . 90.0
0.5
deg
Satellite elevation angle


state
UINT16

n/a

Satellite tracking status.







See below.


cno
UINT8[10]
0 . . . 60
1
dB-Hz
Array of satellite signal to







noise ratios for the past







second. Measurements are







made every 100 ms. Value







at index zero is the oldest.





Note:


To get a real value of the parameter a value from the structure should be multiplied by the scale factor.













TABLE 44







state bit fields:














15
14
13
12
11
10
9
8





reserved 0
reserved 0
reserved 0
reserved 0
reserved 0
reserved 0
reserved 0
Initial









acquisition









in









progress
















TABLE 45







state bit fields:














7
6
5
4
3
2
1
0





Ephemeris
Acquisition
Code
Carrier
Sub
Bit
Delta
Acquisition


data
failed
locked
Pulling
Frame
sync done
Phase
success


available


done
sync done

valid









The GPS_NAV_SW_VERSION output message provides a positioning engine software version string. Message is sent as a reply to the GPS_NAV_POLL_SW_VERSION input message.









TABLE 46









  Include file



  gps_messages.h



Message id:














Value
Macro







6 (0x06)
GPS_NAV_SW_VERSION

















TABLE 47







Message structure


tGPS_NAV_SW_VERSION














Data range






Data
(after de-
Scale




Structure member
type
scaling)
factor
Units
Description





sw_version[100]
UINT8
ASCII


GPS engine




characters


software version.







Version string







is NULL







terminated.







Message length is







variable but does







not exceed







100 bytes.









The GPS_NAV_CLOCK_STATUS output message provides current GPS clock status information. Message is outputted periodically at 1 Hz rate or on demand as a reply to GPS_NAV_POLL_CLOCK_STATUS input message.









TABLE 48









  Include file



  gps_messages.h



Message id:














Value
Macro







7 (0x07)
GPS_NAV_CLOCK_STATUS

















TABLE 49







Message structure


tGPS_NAV_CLOCK_STATUS












Structure
Data
Data range
Scale




member
type
(after de-scaling)
factor
Units
Description















gps_week
UINT16
1 . . .
1

Computed full GPS







week number.


gps_tow
UINT32
0 . . . 604799.99
0.01
sec
Computed GPS time







of the week.


sv_used_cnt
UINT8
0 . . . 12
1

Number of satellites







used in solution.


clk_offset
UINT32
25000 . . . 146000
1
Hz
Computed clock offset


clk_bias
UINT32
0 . . . 0.1
1e−9
sec
Computed clock bias


est_gps_time
UINT32
0 . . . 604799.999
0.001
sec
Estimated GPS time





Note:


To get a real value of the parameter a value from the structure should be multiplied by the scale factor.






The GPS_NAV_ERROR output message outputs notification, warning, and alert messages.









TABLE 50









  Include file



  gps_messages.h



Message id:














Value
Macro







10 (0x0A)
GPS_NAV_ERROR

















TABLE 51







Message structure


tGPS_NAV_ERROR











Structure
Data
Data range
Scale



member
type
(after de-scaling)
factor
Description





err_id
UINT16
0 . . . 0x0FFF
n/a
Notification code




0x1000 . . . 0x1FFF
n/a
Warning code




0x2000 . . . 0x2FFF
n/a
Alert code


param_cnt
UINT16
0 . . . 5
1
Number of 32-bit






parameters in






param[ ]


param[5]
UINT32
UINT32 range
n/a
Array of






information






parameters.






Meaning depends






on error code









The GPS_ADC_ODOMETER_DATA output message provides ADC, odometer and GPIO lines state from tracker. Message is outputted periodically at 1 or 10 Hz rate depending on setting used in GPS_Start( ) function.









TABLE 52









  Include file



  gps_messages.h



Message id:














Value
Macro







45 (0x2D)
GPS_ADC_ODOMETER_DATA

















TABLE 53







Message structure


tGPS_ADC_ODOMETER_DATA














Data range





Structure
Data
(after de-
Scale




member
type
scaling)
factor
Units
Description





current_time
UINT32
>=0
1
ms
Tracker Time, millisecond







counts from tracker reset


adc2_avg
INT16
−8192 . . . 8191
1
n/a
Averaged measurement from







ADC[2] input. See below for







voltage formula.


adc3_avg
INT16
−8192 . . . 8191
1
n/a
Averaged measurement from







ADC[3] input. See below for







voltage formula.


odo_count
UINT16
0 . . . 0xFFFF
1
n/a
Odometer counter







measurement at the most







recent 100 ms tracker input


gpio_stat
UINT8
0 . . . 0xFF
n/a
n/a
GPIO input states at the most







recent 100 ms tracker input.







Bit field, see below.
















TABLE 54







gpio_stat bit field:














7
6
5
4
3
2
1
0





GPIO12
GPIO8
GPIO7
GPIO5
GPIO4
GPIO3
GPIO2
GPIO0


input state
input state
input state
input state
input state
input state
input state
input state
















TABLE 55





GPIOxx state:



















Value
Macro
Description







0

Input pin xx is in low state



1

Input pin xx is in high state










In one implementation, the Voltage formula is Uin [V]=Vref*((adcX_avg+8192)/16384), where: Vref=2.55V, and adcX_avg is a measurement value from message above. The analog to digital converter may, for example, take measurements at 50 Hz rate and the reported value adcX_avg may be an average of the last 5 samples.
The GPS_NAV_COMPLETE output message is sent at the end of the navigation cycle to confirm that the GPS engine has finished a position computation cycle (with or without success). In one implementation, this message is outputted at 1 Hz rate.









TABLE 56









  Include file



  gps_messages.h



Message id:














Value
Macro







47 (0x2F)
GPS_NAV_COMPLETE

















TABLE 57







Message structure


tGPS_NAV_COMPLETE












Structure
Data
Data range (after
Scale




member
type
de-scaling)
factor
Units
Description





control
UINT8
0


Not in use.









The GPS_NAV_TEXT output message outputs debug and development messages in text format.









TABLE 58









  Include file



  gps_messages.h



Message id:














Value
Macro







255 (0xFF)
GPS_NAV_TEXT

















TABLE 59







Message structure


tGPS_NAV_TEXT












Structure
Data
Data range
Scale




member
type
(after de-scaling)
factor
Units
Description





msg_text[256]
UINT8
ASCII


Text of




characters


the message









The GPS_NAV_INITIALIZE input message performs GPS engine re-initialization. Message should be used to perform factory, cold, warm or hot restart.









TABLE 60









  Include file



  gps_messages.h



Message id:














Value
Macro







128 (0x80)
GPS_NAV_INITIALIZE

















TABLE 61







Message structure


tGPS_NAV_INITIALIZE












Structure
Data
Data range (before
Scale




member
type
scaling)
factor
Units
Description





ecef_x
SINT32

1
meters
Approximate ECEF


ecef_y
SINT32

1
meters
position. Those values


ecef_z
SINT32

1
meters
are used by warm start







with initialization only.


clk_offset
SINT32
0, 25000 . . . 146000
1
Hz
Default GPS clock







offset. This value is







used by the factory re-







start only. If zero is







provided here a default







value of 96250 Hz is







used.


gps_tow
UINT32
0 . . . 604799
1
sec.
Approximate GPS time







of the week. This value







is used by warm start







with initialization only


gps_week
UINT16
0 . . .
1

Approximate full GPS







week number. This







value is used by warm







start with initialization







only.


chnl_cnt
UINT8
12
1

Number of channels to







use.


restart_flags
UINT8



Restart configuration







flags. See below for







details.
















TABLE 62







restart_flags bit fields:














7
6
5
4
3
2
1
0














reserved 0
reserved 0
Enable
reserved 0
Restart mode. See below




text

for allowed values.




output
















TABLE 63







Restart mode









Value
Macro
Description





0
GPS_RESTART_HOT
Hot restart


2
GPS_RESTART_WARM_NOINIT
Warm restart with no




initialization


3
GPS_RESTART_WARM_INIT
Warm restart with




initialization (fields ecef_x,




ecef_y, ecef_z, gps_tow,




gps_week are used)


6
GPS_RESTART_COLD
Cold restart


8
GPS_RESTART_FACTORY
Factory restart


Other

Reserved


value
















TABLE 64







Enable text output:









Value
Macro
Description





0

Development text output




(messages GPS_NAV_TEXT)




is disabled


1
GPS_RESTART_TEXTOUT
Development text output




(messages GPS_NAV_TEXT)




is enabled









In one implementation, the navigation engine will initiate restart within one second and a default clock offset value is 96250 Hz. When the actual clock offset is unknown a value of 96250 Hz should be used. However, if the real clock offset is far from a specified value a longer TTFF will be observed.







TABLE 65





Example

















#include “gps_types.h”



#include “gps_interface.h”



/* Forces cold start of GPS receiver: */










tGPS_NAV_INITIALIZE
InitMsg;



tGPS_UINT32
result;









memset( &InitMsg, 0, sizeof(tGPS_NAV_INITIALIZE) );



gps_init.chnl_cnt = 12;



gps_init.restart_flags = GPS_RESTART_HOT |



GPS_RESTART_TEXTOUT;



result = GPS_Input( GPS_NAV_INITIALIZE, (void*)&InitMsg,



sizeof(tGPS_NAV_INITIALIZE) );










The GPS_NAV_POLL_SW_VERSION input message asks for the software version of the position/GPS library.









TABLE 66









  Include file



  gps_messages.h



Message id:














Value
Macro







132 (0x84)
GPS_NAV_POLL_SW_VERSION

















TABLE 67







Message structure


tGPS_NAV_POLL_SW_VERSION












Structure
Data
Data range
Scale




member
type
(before scaling)
factor
Units
Description





control
UINT8
0


Not in use.









The software version string may be returned, for example, in a GPS_NAV_SW_VERSION output message via GPS_Output( ) function.
The GPS_NAV_SET_DGPS_SOURCE input message selects a data source for differential (DGPS) corrections.









TABLE 68









   Include file



   gps_messages.h



Message id:














Value
Macro







133 (0x85)
GPS_NAV_SET_DGPS_SOURCE

















TABLE 69







Message structure


tGPS_NAV_SET_DGPS_SOURCE












Structure

Data range
Scale




member
Data type
(before scaling)
factor
Units
Description





src
UINT8
see below
n/a
n/a
Selects differential







correction data source.







Default is NONE after







factory reset.


freq
UINT32
0


Internal beacon frequency.







Not used, set to 0.


bit_rate
UINT8
0


Internal beacon bit rate.







Not used, set to 0.
















TABLE 70







Differential correction source:









Value
Macro
Description





0
GPS_DGPS_SRC_NONE
Differential corrections are




not used for navigation


1
GPS_DGPS_SRC_SBAS
Selects SBAS as a data source


Other value

Reserved









These settings may be saved in nonvolatile data storage.
The GPS_NAV_POLL_CLOCK_STATUS input message asks for the current GPS clock status of the GPS library.









TABLE 71









   Include file



   gps_messages.h



Message id:














Value
Macro







144 (0x90)
GPS_NAV_POLL_CLOCK_STATUS

















TABLE 72







Message structure


tGPS_NAV_POLL_CLOCK_STATUS












Structure
Data
Data range
Scale




member
type
(before scaling)
factor
Units
Description





control
UINT8
0


Not in use.









The clock status data may be returned in GPS_NAV_CLOCK_STATUS output message via GPS_Output( ) function.
The GPS_NAV_SET_SBAS_PRN input message manually forces PRN for use in SBAS corrections.









TABLE 73









   Include file



   gps_messages.h



Message id:














Value
Macro







170 (0xAA)
GPS_NAV_SET_SBAS_PRN

















TABLE 74







Message structure


tGPS_NAV_SET_DGPS_MODE












Structure
Data
Data range
Scale




member
type
(before scaling)
factor
Units
Description





prn
UINT8
0, 120 . . . 138
1

PRN number, 0 =







Automatic search


reserved_0
UINT32



Reserved


reserved_1
UINT32



Reserved









These settings may be saved in permanent data storage.
The Operating System Interface functions are operating system dependent and are implemented in the open source format available from SiRF Technology, Inc. The functions include Thread, mutex and semaphore functions. Permanent storage and RTC functions may be available depending on hardware availability.







TABLE 75







Thread control functions









Function name
Description
Provided in





OS_Thread_Create( )
Function creates a thread
gps_rtos.c


OS_Thread_Delete( )
Function deletes a thread
gps_rtos.c


OS_Thread_Sleep( )
Function suspends a thread for a
gps_rtos.c



given time
















TABLE 76







Mutex control functions









Function name
Description
Provided in





OS_Mutex_Create( )
Function creates a mutex object -
gps_rtos.c



a software critical section


OS_Mutex_Delete( )
Function deletes a mutex object
gps_rtos.c


OS_Mutex_Enter( )
Function obtains a mutex object
gps_rtos.c


OS_Mutex_Exit( )
Function releases a mutex object
gps_rtos.c
















TABLE 77







Semaphore control functions











Implemented


Function name
Description
in





OS_Semaphore_Create( )
Function creates a semaphore
gps_rtos.c



object


OS_Semaphore_Delete( )
Function deletes a semaphore
gps_rtos.c



object


OS_Semaphore_Wait( )
Function waits for a
gps_rtos.c



semaphore


OS_Semaphore_Release( )
Functions releases a
gps_rtos.c



semaphore object
















TABLE 78







Permanent storage control functions









Function name
Description
Implemented in





OS_Storage_Open( )
Functions opens a storage
gps_rtos.c



system


OS_Storage_Close( )
Functions closes a storage
gps_rtos.c



system


OS_Storage_Write( )
Function writes given words
gps_rtos.c



to the non-volatile storage



area (battery backed RAM,



file, registry, etc.)


OS_Storage_WriteAll( )
Function writes all storage
gps_rtos.c



data to the non-volatile



storage area (battery backed



RAM, file, registry, etc.)


OS_Storage_Read( )
Function retrieves a data from
gps_rtos.c



the non-volatile storage area
















TABLE 79







Real Time Clock control function









Function name
Description
Implemented in





OS_RTC_Read( )
Function returns a current time
gps_rtos.c



from on-board's real time clock.









The OS_Thread_Create( ) function uses an appropriate operating system service to create a thread. The function is called by the GPS engine at the startup to create all desired threads.







TABLE 80







   File


   gps_rtos.c


   Syntax


   tGPS_UINT32 OS_Thread_Create( tGPS_UINT32 thread_id,


                 tGPS_HANDLE function_ptr,


                 tGPS_THREAD *thread_handle )













Parameter
Data range
Units
Description





thread_id
Thread macros defined

Identifier of the thread to



in gps_rtos.h

be created


function_ptr


Thread function


thread_handle


Handle of the created





thread
















TABLE 81







Return values










Return value
Description







GPS_SUCCESS
Thread was created successfully



GPS_RTOS_ERROR
An error occurred










A maximum number of desired threads may be specified by a GPS_RTOS_THREAD_MAX define.
The OS_Thread_Delete( ) function uses appropriate OS service to stop a thread and/or to wait for thread to gracefully stop. Function is called by the GPS engine from GPS_Stop( ) to stop all SiRFNav threads.









TABLE 82









File



gps_rtos.c



Syntax



   tGPS_UINT32 OS_Thread_Delete(tGPS_THREAD



   thread_handle, tGPS_UINT32 timeout )














Parameter
Data range
Units
Description





thread_handle


Thread handle


Timeout

ms
Grace period allowed before





terminating the thread
















TABLE 83







Return values










Return value
Description







GPS_SUCCESS
Thread was deleted successfully



GPS_RTOS_ERROR
An error occurred










Thread identifiers and functions may be specified, for example, in the gps_rtos.h header file.
The OS_Thread_Sleep( ) function uses appropriate OS service to suspend a thread for a given number of milliseconds. Function is called by the GPS engine to suspend current thread temporarily.









TABLE 84









File



gps_rtos.c



Syntax



tGPS_UINT32 OS_Thread_Sleep (tGPS_UINT32 milliseconds )














Parameter
Data range
Units
Description





Miliseconds

ms
Time for what thread will be





suspended
















TABLE 85







Return values










Return value
Description







GPS_SUCCESS
Thread sleep has finished successfully










The OS_Mutex_Create( ) function uses an operating system service to create a Mutex (mutually exclusive) object, or OS-specific equivalent such as a software critical section. This function is called by the GPS engine at the startup to create all desired mutexes.







TABLE 86







File


gps_rtos.c


Syntax


tGPS_UINT32 OS_Mutex_Create( tGPS_MUTEX *mx_handle )













Parameter
Data range
Units
Description





mx_handle


Handle of the created mutex





object
















TABLE 87







Return values










Return value
Description







GPS_SUCCESS
Mutex was successfully created



GPS_RTOS_ERROR
An error occurred










The maximum number of desired mutexes may be specified by a GPS_RTOS_MUTEX_MAX define.
The OS_Mutex_Delete( ) function uses an operating system service to delete a Mutex object. The function is called by the GPS engine at the stopping procedure to delete all used mutexes.







TABLE 88







File


gps_rtos.c


Syntax


tGPS_UINT32 OS_Mutex_Delete( tGPS_MUTEX mx_handle )















Parameter
Data range
Units
Description







mx_handle


Mutex object handle

















TABLE 89







Return values










Return value
Description







GPS_SUCCESS
Mutex was successfully deleted



GPS_RTOS_ERROR
An error occurred










The OS_Mutex_Enter( ) function uses an operating system service to obtain a Mutex object. This function is called by the GPS engine just before entering into a critical section.









TABLE 90









File



gps_rtos.c



Syntax



tGPS_UINT32 OS_Mutex_Enter( tGPS_MUTEX mx_handle )
















Parameter
Data range
Units
Description







mx_handle


Mutex object handle

















TABLE 91







Return values










Return value
Description







GPS_SUCCESS
Mutex was successfully obtained



GPS_RTOS_ERROR
An error occurred










The OS_Mutex_Exit( ) function uses appropriate OS service to release a Mutex object. Function is called by the GPS engine just after leaving from a critical section.









TABLE 92









File



gps_rtos.c



Syntax



tGPS_UINT32 OS_Mutex_Exit( tGPS_MUTEX mx_handle )
















Parameter
Data range
Units
Description







mx_handle


Mutex object handle

















TABLE 93







Return values










Return value
Description







GPS_SUCCESS
Mutex was successfully released



GPS_RTOS_ERROR
An error occurred










The OS_Semaphore_Create( ) function uses an operating system service to create a Semaphore object. The function is called by the GPS engine at the startup to create all desired semaphores.









TABLE 94









File



gps_rtos.c



Syntax



tGPS_UINT32 OS_Semaphore_Create( tGPS_SEMAPHORE



*sem_handle,



tGPS_UINT32 init_value )














Parameter
Data range
Units
Description





sem_handle


Handle of the created





semaphore object


init_value
any UINT32

Semaphore initialization value
















TABLE 95







Return values










Return value
Description







GPS_SUCCESS
Semaphore was successfully created



GPS_RTOS_ERROR
An error occurred










The maximum number of desired semaphores may specified by a GPS_RTOS_SEM_MAX define.
The OS_Semaphore_Delete( ) function uses an operating system service to delete a Semaphore object. The function is called by the GPS engine at the stopping procedure to delete all used semaphores.









TABLE 96









File



gps_rtos.c



Syntax



tGPS_UINT32 OS_Semaphore_Delete( tGPS_SEMAPHORE



sem_handle )
















Parameter
Data range
Units
Description







sem_handle


Semaphore object handle

















TABLE 97







Return values










Return value
Description







GPS_SUCCESS
Semaphore was successfully deleted



GPS_RTOS_ERROR
An error occurred










The OS_Semaphore_Wait( ) function uses an operating system service to wait for Semaphore object. Function is called by the GPS threads to wait for events.









TABLE 98









File



gps_rtos.c



Syntax



tGPS_UINT32 OS_Semaphore_Wait( tGPS_SEMAPHORE



sem_handle, tGPS_UINT32 timeout )














Parameter
Data range
Units
Description





sem_handle


Semaphore object handle


Timeout
0-4000000000 or
ms
Maximum time allowed to wait



GPS_INFINITE

for semaphore
















TABLE 99







Return values








Return value
Description





GPS_SUCCESS
Semaphore was successfully



obtained


GPS_RTOS_ERROR
An error occurred


GPS_RTOS_SEM_WAIT_TIMEOUT
Waiting for the semaphore has



timed out, semaphore was not



obtained.









The OS_Semaphore_Release( ) function uses appropriate OS service to release a Semaphore object. The function is called by the GPS engine to schedule other thread.









TABLE 100









File



gps_rtos.c



Syntax



tGPS_UINT32 OS_Semaphore_Release( tGPS_SEMAPHORE



sem_handle )
















Parameter
Data range
Units
Description







sem_handle


Semaphore object handle

















TABLE 101







Return values










Return value
Description







GPS_SUCCESS
Semaphore was successfully released



GPS_RTOS_ERROR
An error occurred










The OS_Storage_Open( ) function uses an operating system or BIOS service to open a non volatile storage system. The function is called by the GPS engine at the startup to open a storage.









TABLE 102









File



gps_rtos.c



 Syntax



 tGPS_RESULT OS_Storage_Open( void )
















Parameter
Data range
Units
Description







none

















TABLE 103







Return values










Return value
Description







GPS_SUCCESS
Storage has been opened successfully



GPS_RTOS_ERROR
An error occurred










When the nonvolatile storage is not available then function may return GPS_RTOS_ERROR.
The OS_Storage_Close( ) function uses appropriate OS or BIOS service to close a non volatile storage system. The function is called by the GPS engine at the shut down procedure to close a storage.









TABLE 104









File



gps_rtos.c



Syntax



tGPS_RESULT OS_Storage_Close( void )
















Parameter
Data range
Units
Description







none

















TABLE 105







Return values










Return value
Description







GPS_SUCCESS
Storage has been closed successfully



GPS_RTOS_ERROR
An error occurred










When the nonvolatile storage is not available then function may return GPS_RTOS_ERROR.
The OS_Storage_Write( ) function uses appropriate OS or BIOS service to write given words to a non volatile storage system (battery backed RAM, file system, etc.). The function is called by the GPS engine periodically, for example every 30 seconds, to save time, position and ephemeris information. That information is used later to speed up the GPS start procedure (e.g., for hot or warm starts).









TABLE 106









File



gps_rtos.c



Syntax



tGPS_RESULT OS_Storage_Write( tGPS_UINT32 offset,



tGPS_UINT16 *data,



tGPS_UINT16 words )














Parameter
Data range
Units
Description





offset

bytes
Offset from the beginning of





the storage structure where new





data should be written


data


Pointer to the data to write


words

16 bit
Number of 16 bit words to




words
write
















TABLE 107







Return values










Return value
Description







GPS_SUCCESS
Write done successfully



GPS_RTOS_ERROR
An error occurred










The OS_Storage_WriteAll( ) function uses an operating system or BIOS service to write a GPS data structure to a nonvolatile storage system. The function is called by the GPS engine periodically, for example every 30 seconds, to save time, position and ephemeris information. That information is used later to speed up the GPS start procedure (hot or warm starts)









TABLE 108









File



gps_rtos.c



Syntax



tGPS_RESULT OS_Storage_WriteAll( tGPS_UINT8 *data,



tGPS_UINT16 length )
















Parameter
Data range
Units
Description







data


Pointer to the data to write



length

bytes
Length of the data

















TABLE 109







Return values










Return value
Description







GPS_SUCCESS
Write done successfully



GPS_RTOS_ERROR
An error occurred










The OS_Storage_Read( ) function uses an operating system or BIOS service to read GPS data structure from a nonvolatile storage system. The function is called by the GPS engine at the startup to retrieve time, position and ephemeris information. This information is used to speed up the GPS start procedure (e.g., for hot or warm starts).









TABLE 110









File



gps_rtos.c



Syntax



tGPS_RESULT OS_Storage_Read( tGPS_UINT8 *data,



tGPS_UINT16 words )
















Parameter
Data range
Units
Description







data


Pointer to the data to read



words

16 bit
Length of the data





words

















TABLE 111







Return values










Return value
Description







GPS_SUCCESS
Read done successfully



GPS_RTOS_ERROR
An error occurred










The OS_RTC_Read( ) function uses an operating system or BIOS service to read a real time clock information from the host's RTC. The function is called periodically by the GPS engine.









TABLE 112









File



gps_rtos.c



Syntax



tGPS_UINT32 OS_RTC_Read( tGPS_UINT16 *weekno,



tGPS_UINT32 *timeOfWeek )
















Parameter
Data range
Units
Description







weekno
1 ..

GPS full week number



timeOfWeek
0 .. 604799999
ms
GPS time of the week

















TABLE 113







Return values










Return value
Description







GPS_SUCCESS
Read done successfully



GPS_RTOS_ERROR
An error occurred










The tracker communication interface functions allow messages to be sent and received between the tracker hardware and the user programs and position library.







TABLE 114







tracker communication interface functions









Function
Description
Implemented in





GPS_COMM_TRK_Create( )
Creates tracker
gps_comm_trk.c



interface port handle


GPS_COMM_TRK_Delete( )
Deletes tracker
gps_comm_trk.c



interface port handle


GPS_COMM_TRK_Open( )
Opens and
gps_comm_trk.c



configures tracker



port


GPS_COMM_TRK_Reopen( )
Reopens and/or
gps_comm_trk.c



reconfigures tracker



port


GPS_COMM_TRK_Close( )
Closes tracker port
gps_comm_trk.c


GPS_COMM_TRK_Wait( )
Waits for data from
gps_comm_trk.c



the tracker


GPS_COMM_TRK_Read( )
Reads data from the
gps_comm_trk.c



tracker


GPS_COMM_TRK_Write( )
Send commands to
gps_comm_trk.c



the tracker









The GPS_COMM_TRK_Create( ) function uses an OS or BIOS service to create a tracker communication handle. The function is called by the GPS engine at the startup to create a communication handle.









TABLE 115









File



gps_comm_trk.c



Syntax



tGPS_UINT32 GPS_COMM_TRK_Create( tGPS_COMM



*port_handle )














Parameter
Data range
Units
Description





port_handle


Pointer to the communication





port handle
















TABLE 116







Return values










Return value
Description







GPS_SUCCESS
Port handle was successfully created



GPS_COMM_ERROR
Error creating port handle










The GPS_COMM_TRK_Delete( ) function uses an OS or BIOS service to delete a tracker communication handle. The function is called by the GPS engine at the stopping procedure to delete a communication handler.









TABLE 117









File



  gps_comm_trk.c



  Syntax



  tGPS_UINT32 GPS_COMM_TRK_Delete( tGPS_COMM



  port_handle )














Parameter
Data range
Units
Description





port_handle


Pointer to the communication





port handle
















TABLE 118







Return values










Return value
Description







GPS_SUCCESS
Port handle was successfully deleted



GPS_COMM_ERROR
An error occurred while deleting port




handle










The GPS_COMM_TRK_Open( ) function uses an OS or BIOS service to open and configure a tracker communication port. The function is called by the GPS engine at the startup.







TABLE 119







File


gps_comm_trk.c


Syntax


tGPS_UINT32 GPS_COMM_TRK_Open( tGPS_COMM port_handle,


tGPS_UINT32 port_num, tGPS_UINT32 baud_rate )













Parameter
Data range
Units
Description





port_handle


Pointer to the communication port





handle


port_num


Specifies a communication port





where tracker is connected to. 1 =





serial port 1, 2 = serial port 2, . . .


baud_rate
4800, 38400,
bps
Specifies a baud rate at which tracker



57600,

is connected to. Default 2t tracker



115200

baud rate is 38400 bps.
















TABLE 120







Return values










Return value
Description







GPS_SUCCESS
Port was successfully opened



GPS_COMM_ERROR
An error occurred while opening or




configuring the port










The GPS_COMM_TRK_Reopen( ) function uses an OS or BIOS service to re-open a tracker communication port. The function is called by the GPS engine after coming back from a power suspend mode. When power suspend mode is not required then the function may return GPS_SUCCESS only.









TABLE 121









File



gps_comm_trk.c



Syntax



tGPS_UINT32 GPS_COMM_TRK_Reopen( tGPS_COMM



port_handle )
















Parameter
Data range
Units
Description







port_handle


Pointer to the






communication






port handle

















TABLE 122







Return values










Return value
Description







GPS_SUCCESS
Port was successfully re-opened



GPS_COMM_ERROR
An error occurred










The GPS_COMM_TRK_Close( ) function uses an OS or BIOS service to close a tracker communication port. The function is called by the GPS engine at the stopping procedure to close the port.









TABLE 123









File



gps_comm_trk.c



Syntax



tGPS_UINT32 GPS_COMM_TRK_Close( tGPS_COMM



port_handle )
















Parameter
Data range
Units
Description







port_handle


Pointer to the






communication






port handle

















TABLE 124







Return values










Return value
Description







GPS_SUCCESS
Port was successfully closed



GPS_COMM_ERROR
An error occurred










The GPS_COMM_TRK_Wait( ) function uses an OS or BIOS services to wait for data from a tracker communication port. The function is called by the GPS engine to wait for the tracker data.







TABLE 125







File


gps_comm_trk.c


Syntax


tGPS_UINT32 GPS_COMM_TRK_Wait( tGPS_COMM port_handle,


tGPS_UINT32 timeout )















Parameter
Data range
Units
Description







port_handle


Pointer to the






communication






port handle



timeout
0-4000000000 or
ms
Timeout value




GPS_INFINITE

















TABLE 126







Return values










Return value
Description







GPS_SUCCESS
Data from tracker




is available



GPS_COMM_DATA_NOT_AVAILABLE
Error: data from




tracker was not




available within




given time










The GPS_COMM_TRK_Read( ) function uses appropriate OS or BIOS services to read data from a tracker communication port. The function is called by the GPS engine to read tracker data.









TABLE 127









  File



  gps_comm_trk.c



Syntax



  tGPS_UINT32 GPS_COMM_Trk_Read(tGPS_COMM



  port_handle,



        tGPS_UINT8 *data,



        tGPS_UINT32 length,



        tGPS_UINT32 *bytes_read )














Parameter
Data range
Units
Description





port_handle


Pointer to the communication





port handle


data


Pointer to the read data


length
1 . . . 65535
bytes
Number of requested bytes


bytes_read
0 . . . length
bytes
Number of bytes read
















TABLE 128







Return values








Return value
Description





GPS_SUCCESS
Data read was successful


GPS_COMM_DATA_NOT_AVAILABLE
An error occurred









The GPS_COMM_TRK_Write( ) function uses appropriate OS or BIOS services to write data to the tracker communication port. The function is called by the GPS engine to send commands to the tracker hardware.









TABLE 129









File



gps_comm_trk.c



Syntax



tGPS_UINT32 GPS_COMM_Trk_Write( tGPS_COMM



port_handle, tGPS_UINT8 *data, tGPS_UINT32 length )














Parameter
Data range
Units
Description





port_handle


Pointer to the communication





port handle


data


Pointer to the data to send


length
1 . . . 65535
bytes
Number of bytes to send
















TABLE 130







Return values










Return value
Description







GPS_SUCCESS
Data write was successful



GPS_COMM_ERROR
An error occurred










Turning next to FIG. 5, that figure shows a block diagram 500 of the Cooperation between threads, tasks and hardware in one implementation of a host based GPS solution. In particular, the tracker hardware 104 communicates through a serial driver 502 (for example, the Windows CE serial driver). The serial driver 502 communicates and cooperates with a file system 504 (for example, the Windows CE file system), which includes input buffers and output buffers for the communications that will occur.
FIG. 5 shows a pass through data flow path to the tracker hardware 104. The path includes the SendPasahroughDataToTracker thread 506 that forwards data directly from a client program, through a pass through control function 508 to a tracker interface send function 510. In the reception direction, the tracker interface receive function 512 forwards data from the tracker hardware 104 to the navigation/positioning engine queue 514 (if the message is destined for the positioning engine), or to the user interface queue 516 (if the message is destined directly for the user program). The DataForwarder thread 518 removes messages from the user interface queue 516 and sends them via the user callback function 520 to the user program. When the host 102 includes the Component Object Module interface (available from Microsoft), the user callback function 520 may be the IcallBack function.
The receive manager and navigation thread 522 removes messages destined for the GPS library from the positioning engine queue 514, and also places messages destined for the user programs on the user interface queue 516. The messages for the GPS library are processed by the tasks including the NavPeriodicTask 524. A set of shared buffers, control flags, completion flags, and the like 526 are maintained by the GPS library. Finally, it is noted that the COM interface provides a set of control functions 528.
Turning next to FIG. 6, that figure illustrates one execution schedule 600 for the receive manager thread 522 and the NavPeriodicTask 524. In the schedule 600, the NavPeriodicTask 524 runs as a low-priority (background) thread, while the receiver manager and navigation thread 522 run in one normal-priority thread.
With regard to FIG. 7, that figure shows a synchronization diagram 700. The synchronization diagram 700 illustrates the timing and interaction between the threads and tasks shown in FIG. 5.
With reference to FIG. 7, receive manager (RxM) and navigation (Nav) run sequentially in one loop that waits for new data from Tracker Interface (TRK_IF) Receiver before each iteration. Either RxM or Nav may signals NavPeriodicTask 524 to proceed with one iteration of its loop (unless NavPeriodicTask 524 already performing its task, in which case it will finish the task and skip one loop).
The RxM and Nav thread 522 may wait on a Critical Section when writing data to the UI Queue 516, or when sending data to Tracker 104. There will typically be a thread running while RxM&Nav are waiting. In one implementation, NavPeriodicTasks 524 runs at smaller priority than the other tasks and it will not run as long as any other thread is running. In an alternative implementation, NavPeriodicTasks 524 runs at normal priority, but does not present a conflict as long as RxM&Nav have sufficient priority to consume data generated by NavPeriodicTasks 524.
The RxM and Nav thread 522 runs the RxM control task that maintains a state machine for the Rx and manages the state machine transitions based on current state. The RxM communicates with the tracker hardware 104 through the tracker interface. It both sends data and commands to the tracker hardware 104 to pace it through initial acquisition and tracking of SPS satellites, and receives data and status messages from the receiver with raw SPS satellite tracking data. The primary purpose of the RxM task is to manage and control the operation of the tracker hardware 104. It also preprocesses the raw tracker data and submits the processed data to the Navigation Processing Task. The RxM gets scheduled or called by the Nav Task once the tracker hardware 104 starts tracking.
The NavPeriodicTasks thread 524 is a pseudo task that performs miscellaneous support operations for the RxM and Nav tasks. Its functions include determining and performing updates to the satellite state tables, and generating new visible SPS satellite list when new ephemeris data is collected, or whenever it is requested.
The Nav Processor Thread performs position, velocity and time computations based on the RxM generated individual SPS satellite data. This makes use of the functionality offered through the navigation library in optimally computing the navigation position data. The computed navigation data is made available to the Data Forwarding thread. At the beginning of each iteration, the Nay Processor calls or schedules the RxM task to run, and then it performs navigation computations and generates the user position, velocity, and time data. Based on the computation results, if pre-selected error thresholds are exceeded, the Nay Processor may send commands to the receiver, either directly or through the RxM, to force the receiver to reset.
The I/O Reader thread and Tracker Interface Receiver 512 sends data to queues as shown in FIG. 5. In addition, data length error checks may be performed with error counts logged in a global variable. Erroneous message bytes will be reported to the user program through debug messages.
Note that in some implementations, the I/O Writer thread 510 is not used. Instead, its role may been taken by TRK_IF, whose methods are invoked from the RxM+Nav thread 522 and SendPassThruDataToTracker 504. TRK_IF writes directly to the serial port. (All I/O functions will be grouped into one class). In WinCE, buffering is performed on the File System level, which allows TRK_IF to return quickly upon sending data. On Nucleus, additional buffering may be provided.
The DataForwarderThread 518 reads from the UI Queue 516 and calls the user program's ICallBack interface for each binary message to be sent. If the UI queue's Semaphore is still signaled after Callback returns, the DataForwarderThread 518 may continue piping data until the UI queue 516 is empty. In one implementation, the UI Queue 516 is not locked while Callback is being executed, which allows other threads to run while waiting for Callback to return. Client Callback typically puts data in internal storage for another thread to use. Generally, one Callback is called at a time. The UI Queue 516 is prioritized and it will put pass-thru messages before all others in the queue.
The SendPassThruDataToTracker function 506 is an API call for sending pass-thru messages from the user program to the tracker hardware 104. Note that the pass through control function 504 may be implemented as a filter to enable or disable pass-thru messages:
A Shutdown may be performed by purging all queues and I/O. For example, 300 ms (enough for RxM&Nav to complete) may then be given for threads to complete. Although some threads may not complete in that time, such as the DataForwarderThread 518 (that may be waiting for Callback to return), and NavPeriodicTask 524, for which there may or may not be a provision to interrupt long-term calculations. Regardless, threads which do not complete on time are terminated.
The following synchronization objects may be used: a Semaphore and Critical Section in UI Queue 516 for triggering UI output, a Semaphore and Critical Section in Trk2Nav Queue 514 for triggering Nav update, a Positioning/Navigation Library sync flag (from NavPeriodTasks to RxM and Nav), and a shutdown semaphore and flag. Note that the Critical Section(s) in the Tracker Interface are for protecting access to the serial port.
Queues may have the following API and features: Constructor/destructor, void *GetBuffer(int priority, long size) to obtain a pre-allocated, buffer for Put( ) void Put( ) to queues the buffer with specified priority, void *BeginGet( ) to waits until data ready or shutdown, void EndGet( ), void Remove( ), void Purge( ) to cancel all BeginGet calls, an internal Semaphore for notifying BeginGet( ) when data is ready, and an internal Critical Section.
With regard to error checking, all queue overruns, I/O errors, timeouts and COM errors may optionally be reported to client, packaged in debug messages, UI queue 516 overruns will be reported as an error to user program, Tracker message time-outs may be handled by Nav, and Trk2Nav Queue 514 overruns may be signaled to RxM and Nay.
It is further noted that the Windows registry may provide a mechanism for configuring thread priorities (that may, for example, be set once at startup and remain unchanged during execution), I/O buffer sizes, and queue sizes. Note that the SetupComm( ) function may be used to increase the size of existing WinCE I/O buffers. Doing so prevents input data loss under stress conditions. This may also be configurable through registry, and default values may be chosen to accommodate several seconds of I/O (e.g., 4 kb for input and 1 kb for output).
The foregoing description of an implementation of the invention has been presented for purposes of illustration and description. It is not exhaustive and does not limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practicing of the invention. For example, the described implementation includes software but the present invention may be implemented as a combination of hardware and software or in hardware alone. Note also that the implementation may vary between systems. The invention may be implemented with both object-oriented and non-object-oriented programming systems. The claims and their equivalents define the scope of the invention.

## Claims

1. A system for processing positioning signals, the system comprising:
a mobile phone including:
an input interface receiving input from a user of the mobile phone;
a display outputting information to the user of the mobile phone;
a tracker hardware interface configured to receive positioning information from a tracker hardware internal or external to the mobile phone, wherein the tracker hardware acquires and tracks satellite signals;
a memory including a GPS library having: 1) a GPS Engine, 2) a user interface, 3) a tracker interface, and 4) an operating system interface, the tracker interface configured to communicate with the tracker hardware through the tracker hardware interface, the user interface configured to provide communication between the GPS library and a plurality of respectively different user programs that utilize a location of the mobile phone computed by the GPS Engine, the GPS library using the operating system interface to call operating system functions; and
a processor,

wherein at least one of the user programs calls a GPS_start function that uses the user interface to instruct the GPS Engine to compute the location of the mobile phone, and
in response to the GPS_start function being called, the GPS engine computes the location of the mobile phone based on the positioning information obtained by the tracker interface and calls a GPS_output function that uses the user interface to output the location of the mobile device to the at least one user program.

2. The system of claim 1, wherein the tracker hardware interface comprises a serial interface.

3. The system of claim 1, wherein the user program calls a GPS_Input function that uses the user interface to send instructions to the GPS engine.

4. The system of claim 3, wherein a configuration instruction for configuring the GPS engine is sent to the GPS engine through the user interface using the GPS_Input function.

5. The system of claim 1, wherein the user programs includes at least one of: a mapping program displaying the location of the mobile phone, a course charter program displaying a path traveled by the mobile phone and a location aid program displaying location information of the mobile phone.

6. The system of claim 1, wherein the user program calls a GPS_Stop function that uses the user interface to instruct the GPS engine to stop computing the location of the mobile phone.