Abstract:
A half duplex digital communications system and control means providing a data interface to a plurality of radio transceivers such as between a personal computer or other information processing device to one or more radio transmitter/receiver systems having a serial data interface in a manner that provides control of the radio and means to send and receive data via the radio without regard to the characteristics of the radio or its serial interface. A common control protocol is employed to control the radio transmitter/receiver device in a generic manner through software implementation, allowing compatibility with future data systems.

Description:
PRIORITY CLAIM UNDER 35 U.S.C. §119(e) 
       [0001]    This patent application claims the priority benefit of the filing date of a provisional application Ser. No. 60/573,984, filed in the United States Patent and Trademark Office on May 24, 2004. 
       CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0002]    The present application is a divisional application of and claims priority from related, co-pending, and commonly assigned U.S. patent application Ser. No. 11/007,774 filed on Dec. 8, 2004, entitled “Apparatus and Method for Providing a Data Interface to a Plurality of Radio Transceivers” all by David Keppler and Nathan Lutchansky. Accordingly, U.S. patent application Ser. No. 11/007,774 is herein incorporated by reference. 
     
    
     STATEMENT OF GOVERNMENT INTEREST 
       [0003]    The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment of any royalty thereon. 
       BACKGROUND OF THE INVENTION 
       [0004]    Radio transmitter/receiver systems designed and built since the 1950&#39;s often include data communications capabilities in addition to or instead of voice/audio communications capabilities. The most common interface for connecting data communication equipment (DCE) like radio transmitters and receivers to data terminal equipment (DTE) such as personal computers is the serial interface, defined by the Electronics Industry Alliance (EIA) standards RS-232, RS-422, RS-530, and others. 
         [0005]    Serial interfaces provide a common electrical interface for sending and receiving streams of data as a sequence of voltage levels in which one voltage level indicates a digital one (1) and a different voltage level indicates a digital zero (0). Some serial interfaces, known as synchronous serial interfaces, provide timing information in the form of a separate clock signal by which the transmitter and receiver synchronize the rate at which data flows through the interface. Asynchronous serial interfaces do not have this separate clock signal and rely on oscillators within each device to maintain implicit timing. Serial interfaces may also contain separate control signals to provide status information, enable and disable the flow of data, and/or manipulate the state of the DCE. 
         [0006]    Radio transmitter/receiver systems in use today may implement any one of a wide range of different serial standards and configurations, but the most common DTE in use today is the personal computer (PC) which only provides an asynchronous RS-232 interface. As a result, PCs are unable to utilize many radio transmitter/receiver systems that provide a serial interface based on a different standard, and are unable to take advantage of advanced wireless communications protocols that require a synchronous serial interface between the PC and the radio. 
         [0007]    To alleviate this incompatibility, specialized hardware in the form of add-on boards is commercially available that augments standard PCs with additional serial interfaces that are compatible with some radios. However, this hardware is only compatible with a limited number of commonly-used radios, and the add-on boards are specific to the form-factor of the PC, depending on whether the PC is intended for a desktop, industrial, or mobile environment. 
         [0008]    Interfacing with radio transmitter/receiver systems using serial links also imposes additional restrictions on the DTE. Most radio equipment operates only in a half-duplex mode, in which a radio device is unable to transmit and receive simultaneously. The DTE must control the direction of data exchange by manipulating the “push-to-talk” (PTT) control signal on the serial interface to activate and de-activate the transmitting circuitry on the radio device. Further, many radio transmitters impose additional time delay requirements when transitioning between transmit and receive mode; for example, a transmitter may require several hundred milliseconds for the amplifiers to ramp up to full power before data may be sent, or the data modulator may require a short delay to finish flushing all of the data to be transmitted out of the internal buffers. These timing requirements often necessitate custom software on the DTE that is specific to the serial interface circuitry and/or radio system. 
         [0009]    For some uses, particularly in the military environment, a single PC must be able to interface with multiple radios to provide services that translate between or aggregate the communications capabilities of multiple radio links. These radios are often located distant from one another due to antenna positioning requirements, physical space constraints, or safety reasons. Standard serial interfaces typically frustrate the implementation of such multi-radio systems due to the high cost and technical difficulty of extending serial links more than a few feet from the DTE to the DCE. Providing a simple and low-cost means of extending the range of the link between a PC and a radio would increase the potential capabilities of radio data systems. 
         [0010]    Prior art exists that solves some, but not all, of these issues in a limited environment for some radio systems. Remote control units for radios are able to extend the serial link between the DTE and the radio for hundreds of feet or even several miles, but these units are specific to a particular model of radio system and the serial interface is still unlikely to be compatible with a standard PC. Converters are available to interface from certain radio-specific serial interfaces to a common PC serial interface, but these converters prevent the use of more efficient data encoding mechanisms and do not provide a means of extending the distance between DTE and radio. 
       OBJECTS AND SUMMARY OF THE INVENTION 
       [0011]    It is an object of the present invention to provide a half duplex digital communications system and control means for interfacing with radio transmitter/receiver systems having a serial interface that supports a plurality of serial interface standards. 
         [0012]    It is a further object of the present invention to provide a method and apparatus for controlling the operation of and sending and/or receiving data to and from a radio transmitter/receiver system through a standard data interface available on common PCs. 
         [0013]    It is still a further object of the present invention to provide a method and apparatus for providing a common control protocol to interface with a radio transmitter/receiver system that is independent from the characteristics of the particular radio. 
         [0014]    It is yet still a further object of the present invention to provide a method and apparatus for extending access to a radio transmitter/receiver system over long distances by carrying a common control protocol over existing data networks. 
         [0015]    An additional object of the present invention is to provide a method and apparatus for encapsulating and decapsulating data that is sent and received via a radio transmitter/receiver system in a plurality of serial formats, where the formats are implemented in general-purpose processing units and can be updated electronically. 
         [0016]    The invention disclosed herein provides a method and apparatus for connecting a DTE such as a PC or other information processing device to a radio transmitter/receiver system in a manner that allows the DTE to control the radio and send and receive data via the radio using a common control protocol independent of the type of radio device in use and without regard to the serial interface standard supported by the radio device. The DTE may communicate with the invention via a data interface or network protocol commonly found on PCs, such as an asynchronous serial interface, the Universal Serial Bus (USB), or an Internet Protocol (IP) network. 
         [0017]    According to an embodiment of the invention, [TBC] 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  depicts a block diagram of the components of the invention relative to the systems with which it commonly interfaces. 
           [0019]      FIG. 2  depicts a detailed block diagram of the invention. 
           [0020]      FIG. 3  depicts the synchronous data sampler/driver of the present invention. 
           [0021]      FIG. 4  depicts the DTE interface circuits in three different embodiments of the present invention. 
           [0022]      FIG. 5  depicts the flow of data through one of the embodiments of the present invention. 
           [0023]      FIG. 6  depicts the flow of data through alternate embodiments of the present invention. 
           [0024]      FIG. 7  depicts a flow diagram of the steps for interpreting commands defined in the common control protocol of the present invention. 
           [0025]      FIG. 8  depicts a flow diagram of the steps for transmitting data via synchronous serial interfaces. 
           [0026]      FIG. 9  depicts a flow diagram of the steps for receiving data via synchronous serial interfaces. 
           [0027]      FIG. 10  depicts a typical application scenario for the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0028]    Referring to  FIG. 1 , a preferred embodiment of this invention comprises a general-purpose central processing unit (CPU)  100 , a radio data serial interface circuit  110 , a radio control serial interface circuit  120 , and a data terminal equipment (DTE) interface circuit  300 . 
         [0029]    CPU  100  executes a program that interacts with the DTE through a control channel via the DTE interface  300 , with which it exchanges commands using the common control protocol. These commands enable the DTE to pass data through the invention via the radio data serial interface  110  and the radio control serial interface  120  to the radio transmitter/receiver device. 
         [0030]    Referring to  FIG. 2 , serial interface  200  is depicted in detail, showing the components present in both the radio data serial interface  110  and the radio control serial interface  120 . Serial interface  200  comprises a universal serial interface driver  210 , a selectable push-to-talk (PTT) personality conversion logic circuit  220 , a clock generator  230 , a transmit clock selector switch  240 , a data signal switch/multiplexer  250 , a universal asynchronous receiver/transmitter (UART)  260 , and a synchronous data sampler/driver  270 . The push-to-talk personality conversion logic  220  is not present in the radio control serial interface circuit  120 . 
         [0031]    Universal serial interface driver  210  converts between one of many selectable serial interface electrical standards and the digital logic levels used by the other components of the invention, providing a means of connecting to data serial interfaces on many types of data radios. Clock generator  230  and transmit clock selector switch  240 , when necessary for synchronous operation, provide the selected transmit clock signal  241  for the synchronous data sampler/driver  270 , and can source the clock from the serial interface transmit clock signal  213 , the serial interface receive clock signal  214 , or the clock generator  230 . Data signal switch/multiplexer  250  activates either the UART  260  or the synchronous data sampler/driver  270 , depending on whether an asynchronous mode or a synchronous mode is selected. UART  260 , when active, receives asynchronous, character-framed data from the data signal switch/multiplexer  250  and passes the data by octet to the CPU  100 ; and receives data to be transmitted from the CPU  100  (see  FIG. 1 ) and transmits it through the data signal switch/multiplexer  250  in character-framed format. Synchronous data sampler/driver  270 , when active, receives synchronous data from the data signal switch/multiplexer  250  and passes the data by octet to the CPU  100  (see  FIG. 1 ); and receives data to be transmitted from CPU  100  (see  FIG. 1 ) and transmits it through data signal switch/multiplexer  250 . Synchronous data sampler/driver  270  can be updated electronically to support any serial data format. The present embodiment of the invention supports several different formats, including character framing, High-level Data Control Link (HDLC), and a well-known method for framing characters on noisy radio channels. PTT personality conversion logic circuit  220 , present only in the radio data serial interface circuit  110 , creates a selectable logical mapping between PTT signal  221  supplied by CPU  100  and the control signals exposed on radio data serial interface  219 . 
         [0032]    Referring to  FIG. 3 , synchronous data sampler/driver  270  comprises two general-purpose processing units, one of which is sampler  271  and one of which is driver  272 . Sampler  271  reads data from serial interface receive signal  212 , governed by receive clock signal  214 , and converts the signal into octets to be passed to CPU  100  (see  FIG. 1 ) for delivery to the DTE. The driver  272  receives octets from the CPU  100  (see  FIG. 1 ) and sends them in a serial fashion to the serial interface transmit signal  211 , governed by the selected transmit clock signal  241 . The programs executed by sampler  271  and driver  272  determine the serial data framing and synchronization format implemented by the invention, and thus the invention is able to support new framing formats through a software update without any hardware modifications. 
         [0033]    Three methods for interfacing the invention to the DTE are shown in  FIG. 4 . In one embodiment of the invention, DTE interface  300  (see  FIG. 1 ) is comprised of a network interface  310  used to send and receive data over a data network. The DTE communicates with the invention by establishing a connection using a network protocol such as Transmission Control Protocol/Internet Protocol (TCP/IP), over which it performs commands using the common control protocol. 
         [0034]    In another embodiment of the invention, DTE interface circuit  300  (see  FIG. 1 ) is comprised of a Universal Serial Bus (USB) interface  320 , which connects to the corresponding USB interface on the DTE. The DTE performs commands using the common control protocol encapsulated within standardized USB protocols. 
         [0035]    In yet another embodiment of the invention, DTE interface circuit  300  (see  FIG. 1 ) is comprised of an asynchronous serial port  330 , which connects to a serial port on the DTE. The DTE performs commands using the common control protocol on the serial link thus established. 
         [0036]    The flow of data through the invention in the first embodiment is shown in  FIG. 5 . The use of a data network, in this case the Transmission Control Protocol/Internet Protocol (TCP/IP), provides the communications medium between the invention and the DTE, over which the common control protocol and data are carried. Three TCP/IP ports are utilized: bi-directional TCP/IP common control protocol port  710  carries the commands and responses for the common control protocol, including the data to be transmitted via the radio transmitter, between the DTE and common control protocol interpreter  400 ; uni-directional TCP/IP data receive port  720  which carries the data received by the radio receiver; and bi-directional TCP/IP radio control port  730  which carries the control data between the DTE and the radio transmitter/receiver device control serial port. Buffers  711 ,  721 ,  731 ,  732  are utilized between the serial interfaces  110 ,  120  and the DTE to accommodate network and DTE timing issues and latency common to PC and data network operation. 
         [0037]    The flow of data through the invention in the second and third embodiments is shown in  FIG. 6 . The Universal Serial Bus (USB) or asynchronous serial interfaces provide the communications medium for the common control protocol and data, utilizing two physical or logical connections between the invention and the DTE. A first USB/Serial port connection  810  carries the commands and responses for the common control protocol, including the data to be transmitted via the radio transmitter, between the DTE and the common control protocol interpreter  400 . This connection also carries the data received by the radio receiver, necessitating the use of a well-known encapsulation mechanism to allow the DTE to separate the protocol responses from the received data. The second USB/Serial port connection  820  carries the control data between the DTE and the radio transmitter/receiver device control serial port. Buffers  811 ,  812 ,  821 ,  822  are utilized between serial interfaces  110 ,  120  and the DTE to accommodate DTE latency common to PC operation. 
         [0038]    CPU  100  (see  FIG. 1 ) of the invention executes a program  400 , shown in  FIG. 7 , that processes commands and returns replies formatted in the common control protocol. These commands may cause the radio transmitter to be activated or de-activated, cause data to be sent to the radio data serial interface circuit for transmission via the radio device, or set or retrieve parameters affecting the operation or configuration of the invention. The program normally waits in an idle state for commands to be received  401 . 
         [0039]    When a command is received to instruct the invention to activate the radio transmitter  411 , the invention verifies that the radio device is not currently receiving data  412 , sends a response/acknowledgement to DTE  413 , activates the PTT signal  414 , waits a pre-determined period of time for the radio transmitter to become ready  415 , and returns to idle state  401 . 
         [0040]    When a command is received to instruct the invention to send data via radio  421 , the invention copies the specified data from the DTE to the radio data serial interface circuit to be sent by the radio transmitter  422 , and returns to an idle state  401 . 
         [0041]    When a command is received to instruct the invention to de-activate the radio transmitter  431 , the invention flushes the remaining data from the transmit buffer  432 , sends a response/acknowledgement to the DTE  433 , waits a pre-determined period of time for the radio transmitter to become idle  434 , de-activates the PTT signal  435 , and returns to the idle state  401 . 
         [0042]    Other commands may allow the DTE to request that the invention query  441  or store  442  configuration parameters or statistics  443  relating to the operation of the invention. 
         [0043]    Driver  272  (see  FIG. 3 ) software executes the following steps, shown in  FIG. 8 : an octet to be transmitted is received  510  from the CPU  100  (see  FIG. 1 ); the octet is formatted into an internal buffer according to the encoding method specified for the currently-used framing format  520 ; when a clock edge is detected  530  on selected transmit clock signal  241  (see  FIG. 3 ), the next bit of the internal buffer is transmitted  540  on the serial interface transmit signal  211  (see  FIG. 3 ); if all bits in the internal buffer have been sent, the program returns to the start to receive another octet  550  from the CPU  100  (see  FIG. 1 ). 
         [0044]    Sampler  271  (see  FIG. 3 ) software executes the following steps, shown in  FIG. 9 : when a clock edge is detected  610  on the serial interface receive clock signal  214  (see  FIG. 3 ), a data bit is sampled  620  from the serial interface receive signal  212  (see  FIG. 3 ); if sampler  271  (see  FIG. 3 ) has synchronized itself with the incoming data stream, the program continues, otherwise it returns to the start  630 ; the incoming bit is decoded  640  based on the rules specified in the currently-used framing format and combined with the other bits in the internal buffer; if sampler  271  (see  FIG. 3 ) has received a complete octet of data  650 , it delivers the decoded octet to the CPU  660 ; and the program returns  610  to waiting to receiving another bit. 
         [0045]      FIG. 10  depicts a typical application scenario for the present invention. One or more radio transmitter/receiver devices with data capability  910  are each attached to the invention  920  via both the radio data serial interface and the radio control serial interface, and the functionality of the radio transmitter/receiver devices is exposed to the DTE  940 . The invention may be connected to the DTE through a data network  930  using a network link  950 , or the invention may be connected through a direct link  960  such as USB or asynchronous serial. 
         [0046]    While the preferred embodiments have been described and illustrated, be it known and understood that the present invention is not limited to those precise embodiments described herein, and that various substitutions, equivalents, adaptations and modifications of the invention may be made thereto by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.