Abstract:
The invention relates to an information handling system comprising a handheld device operable independently and having a first connector for external connection, wherein the handheld device functions in accordance with a first protocol and a second protocol; a first appendant device for the handheld device having a second connector for connecting to the first connector, wherein the first appendant device cooperates with the handheld device according to the first protocol inasmuch as the second connector is connected to the first connector; and a second appendant device for the handheld device having a third connector for connecting to the first connector, wherein the second appendant device cooperates with the handheld device according to the second protocol inasmuch as the third connector is connected to the first connector; wherein the first connector has connector pins whose number is less than the number specified in the first protocol for successful signal transmission between the handheld device and the first appendant device.

Description:
REFERENCE TO RELATED APPLICATIONS  
         [0001]    The present application claims priority to Taiwan application NO.090116627 entitled “Apparatus and method of expansion interface converter for handheld device” filed on July 7, 2001.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to method and apparatus for obtaining flexibility in using an electronic device having an expansion interface that allows expansion modules with additional functionalities to be incorporated. More particularly, it relates to method and apparatus for converting signals and switching between interfaces of a handheld electronic device for correct connection to expansion modules.  
           [0004]    2. Description of the Related Art  
           [0005]    Personal digital assistants, or PDAs, have become popular computer products in recent years. They are designed to be light-weighted, of small size that fits into the hands of the user, and can be conveniently put into pockets, which makes them highly portable as compared to heavy and sometimes cumbersome notebooks. The first PDA only allows users to edit and store messages and to perform simple word processing functions. Through the years the technology for PDAs has improved greatly and most of the important functions found in desktop or laptop computers have counterparts on PDAs, though specially adapted to conform to small memory and display.  
           [0006]    A common feature of PDA is that it can transfer data with other computers through a mediating device called cradle. A typical cradle utilizes RS-232 as the transmission standard to allow signal transfer between the PDA and, say, a desktop computer. The cradle can also serve as a battery charger for the PDA.  
           [0007]    Some PDAs also come with a jacket into which they can slide. The jacket has a PCMCIA or COMPACT FLASH slot that can receive expansion cards or functional modules so that additional functions or memory can be incorporated into the PDAs.  
           [0008]    For the reason that RS-232 protocol used in a cradle, which is serial, is different from PCMCIA or COMPACT FLASH protocol used in a jacket, which is parallel, a PDA that can connect to the cradle and the jacket has to resort to two separate interfaces for correct connection, one serial and the other parallel, respectively. That is, there exist on the PDA at least two interfaces, one being RS-232 with 9 pins and the other being, say, PCMCIA with 68 pins, which results in a total number of connector pins up to eighty, and even more if still other interfaces are provided on the PDA. To accommodate these connector pins leads to occupation of excess space within the PDA and is in conflict with the requirement of compactness for handheld devices. Furthermore, exposing connector pins on the housing makes the PDA lose its appealing look to customers. It is needed therefore to reduce the total number of pins of a PDA so as to make it more compact and more appealing to the eye.  
         SUMMARY OF THE INVENTION  
         [0009]    In order to circumvent the shortcomings of the prior art outlined above, the present invention reduces the number of pins required of the PDA connector for connecting to a jacket by employing a parallel-serial conversion. According to one embodiment of the present invention, parallel signals of the PDA are bidirectionally converted into serial signals that can be transmitted through a compact connector interface to the jacket. Similarly, parallel signals of the jacket are bidirectionally converted into serial signals that can be transmitted though a compact connector interface to the PDA. When the PDA and the jacket are connected, straightforward parallel transmission over the PDA-jacket interface is replaced by first converting parallel signals into serial signals that are then transmitted over the compact connector interface and finally recovering the parallel signals from the serial signals transmitted. The reduction in pin number on the compact connector interface is proportional to the parallel-serial conversion ratio.  
           [0010]    In another embodiment of the present invention, the inventive PDA is capable of connecting to a cradle using the same compact connector interface for connecting to the jacket. This is made possible by incorporating into the PDA a switch circuit that switchably connects either the serial signals for the cradle or the parallel signals for the jacket to the compact connector interface. A monitor means is also incorporated into the PDA that monitors the status of the compact connector interface for transmitting correct signals to the connected device accordingly.  
           [0011]    Accordingly, the object of the present invention is to provide a method and apparatus for reducing the number of pins and the size of the connector interface between a PDA and its jacket.  
           [0012]    Another object of the present invention is to provide a method and apparatus by which a PDA is able to connect to and communicate with its jacket and its cradle using a connector.  
           [0013]    Still another object of the present invention is to provide a method and apparatus allowing a handheld device to connect to and communicate with two supplement devices using different transmission standards, one parallel and the other serial, through a compact connector. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The following detailed description, which is given by way of example, and not intended to limit the invention to the embodiments described herein, can best be understood in conjunction with the accompanying drawings, in which:  
         [0015]    [0015]FIG. 1 illustrates the inventive PDA that can connect to an expansion module through a jacket.  
         [0016]    [0016]FIG. 2 illustrates the different sizes of the interface on PDA, wherein FIG. 2 a  illustrates the large size of the interface of the prior art PDA, and FIG. 2 b  illustrates the reduced size of the interface of the inventive PDA.  
         [0017]    [0017]FIG. 3 illustrates one embodiment of the present invention wherein the parallel interface between a PDA and its mating jacket is converted into a serial interface.  
         [0018]    [0018]FIG. 4 illustrates in accordance with the present invention the conversion between parallel signals and serial signals, wherein FIG. 4 a  illustrates the serial-to-serial conversion and FIG. 4 b  illustrates the serial-to-parallel conversion.  
         [0019]    [0019]FIG. 5 illustrates the inventive PDA capable of communicating with a desktop computer through a docking cradle.  
         [0020]    [0020]FIG. 6 illustrates one embodiment of the present invention wherein the serial interface that replaces the parallel interface between a PDA and its mating jacket is made switchable for transmitting RS-232 signals between the PDA and its cradle. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    With reference to the accompanying drawings the novelty and inventiveness of the present invention are described below. Though the following description pertains to PDA device and relating docking cradle and jacket, it is understood that the present invention can be applied to computer systems not under these names.  
         [0022]    [0022]FIG. 1 illustrates the inventive PDA that can connect to an expansion module through a jacket. PDA  100  includes function keys  104  for performing certain operations when depressed, and a display  102  for showing messages and data to the user. As a common feature, the display  102  is usually covered with a touch-sensitive screen and can receive user input by touching the screen with either fingertip or stylus. This allows easy control and reduces the number of function keys to a minimum. Connector  106  is provided on the lower end of the PDA  100  and is used to connect to mating connector  108  of jacket  200 . The jacket  200  has such a shape that when the PDA  100  has been slid in, it covers substantially all the PDA  100  except the display  102  and function keys  104 . An expansion slot  202  is provided on a side of the jacket  200  for receiving expansion card  300 . Through the jacket  200 , the PDA  100  is able to transfer data with the expansion card  300  and thereby additional functions can be performed cooperatively. For example, the expansion card  300  can be a radio receiver module that, when slotted into the jacket  200  connected to the PDA  100 , turns the PDA  100  into a radio receiver. Or it can be a flash memory card that provides more memory space to the PDA  100 . The functions that the expansion card  300  can offer are various.  
         [0023]    In the prior art, for an expansion card following either PCMCIA or COMPACT FLASH standard, the connector of a PDA and the corresponding connector of its jacket both have 68 pins or 50 pins for connection, respectively. In the present embodiment, the number of pins needed for the connector  106 , and connector  108 , is reduced by converting parallel signals of either PCMCIA or COMPACT FLASH format into serial signals. Because serial signals requires less connector pins for representing same data bytes than parallel signals, the size of the connector  106  and  108  can be compacted. FIG. 2 illustrates the different sizes of the interface on PDA for comparison, wherein FIG. 2 a  illustrates the large size of the connector  106 ′ of a typical PDA  101 , and FIG. 2 b  illustrates the reduced size of the connector  106  of the inventive PDA  100 . As the connector  106  is compacted, space is spared for other use inside the inventive PDA  100 . The compactness is advantageous in making the inventive PDA  100  more attractive to users.  
         [0024]    [0024]FIG. 3 is a schematic diagram of the inventive PDA of FIG. 1 for illustrating how parallel signal transmission between the PDA  100  and its mating jacket  200  are converted into serial signal transmission in order to reduce the number connector pins. In this diagram, a set of parallel signals is represented by a solid arrow headed symbol, indicating that the number of pins is of a great amount, and a set of serial signals is represented by a linear arrow headed symbol, indicating that the number of pins is of a small amount. The symbols representing either parallel or serial signals are made two-way arrow headed to reflect that the transmission is bi-directional. For simplicity, only interface components relating to the present invention are shown in this diagram.  
         [0025]    The PDA  100 , the jacket  200 , and the expansion card  300  have parallel interface  110 ,  210 , and  310 , respectively, for parallel transmission. The interface  110  in this diagram signifies a part of the circuitry inside PDA  100  on which functions such as editing and browsing are performed and parallel signals  120  are generated and transferred. In the prior art, it is directly connected to a parallel connector for output. For parallel transmission, the connector would require too many pins the disadvantages of which are what the present invention sets out to overcome. Interface  310  is to be connected directly to interface  210  for transmitting parallel signals in the way shown in FIG. 1. For connection between interface  110  and interface  210 , they are first converted into serial interface  150  and  250 , respectively, for the purpose of reducing the number of pins that carry the transmission signals. The PDA serial interface  150  and the jacket serial interface  250  are connected through connector  106  and  108  as described in FIG. 1. On the side of the PDA  100 , the parallel signals  120  transmitted by the parallel interface  110  are converted into serial signals  140  of the serial interface  150  using a first parallel-serial converter  130 . Similarly, on the side of the jacket  200 , the parallel signals  220  of the parallel interface  210  are converted into serial signals  240  of the serial interface  250  using a second parallel-serial converter  230 . The parallel-serial signal conversion in the first converter  130  and second converter  230  is bi-directional, which is determined by respective directional control signal DIR 1  and DIR 2 . To achieve parallel-serial conversion the first converter  130  and the second converter  230  also require clock signals that determine the sampling rate. Clock signal CLK 1  and CLK 2  serve this function, and are kept at equal rates to maintain compliance between PDA signals and jacket signals. By introducing the first converter  130  and the second converter  230  between the parallel interface  110  and parallel interface  210 , which used to connect to each other straightforwardly in the prior art, parallel signals between the PDA  100  and the jacket  200  are transmitted through serial interface  150  and serial interface  250  with reduced number of connector pins.  
         [0026]    There are ways for converting parallel signals to serial signals. A method is illustrated in FIG. 4, wherein FIG. 4 a  illustrates the forward, parallel-to-serial, conversion and FIG. 4 b  illustrates the backward, serial-to-parallel, conversion.  
         [0027]    The second converter  230  operates in the same manner as the first converter  130  described below. As understood by one skilled in the art, the forward conversion of parallel signals carried on a set of pins into serial signals carried on a set of pins of lesser number is achieved by rearranging the parallel signals in such a way that, within one clock cycle of the parallel signals, parallel signals carried on a particular number of pins are collected and sequentially combined to generate a serial signal that is to be fed into one pin of the serial interface. In FIG. 4 a , DIR 1  is brought high to indicate that the signal flow is from the parallel interface  110 , with clock signal CLKp, to serial interface  150 , with clock signal CLK 1 . Because the clock rate, or clock speed, of CLK 1  is faster than that of CLKp, it is possible for a serial pin to read or sample, within one cycle of CLKp, a plurality of parallel signals on the basis of shorter cycles of CLK 1 . In the present embodiment, the clock speed of CLK 1  is eight times faster than the speed of CLKp, so that in one cycle of CLKp serial pin Sn can receive signals B 0  to B 7  from eight parallel pins P 0  to P 7 , respectively, thus effecting the forward signal conversion and reducing the number of pins required for signal transmission. Similarly, the backward conversion of a serial signal back to parallel signals can be obtained by reversing the operations just described in the forward conversion. In FIG. 4 b , DIR 1  is brought low to indicate the backward signal flow. For each cycle of CLK 1 , the signals B 0  to B 7  carried on serial pin Sn are sequentially read back to parallel pins P 0  to P 7 , respectively. The readback operation is completed in one cycle of CLKp. The above explains the parallel-serial conversion in the first converter  130  and the second converter  230 .  
         [0028]    According to the conversion method described above, for fixed 68 pins of PCMCIA interface functioning with less than 8 MHz clock frequency under normal operating conditions, acceptable performance of the PDA  100  and the jacket  200  can be obtained when CLK 1 , as well as CLK 2 , are set to be around 50 MHz and the parallel-to-serial conversion ratio is set to be eight, with one serial signal representing eight separate parallel signals as described in FIG. 4 a  and FIG. 4 b . Under such configuration, eight pins are sufficient on serial interface  150  and  250  for transmitting PCMCIA signals, excluding GND, RSRVD, and Vcc pins. This has been described in FIG. 3. Additional pins are required for transmitting GND and Vcc signals, which are omitted to simplify the drawing.  
         [0029]    It should be pointed out that one is able to modify the clock rates of the clock signal CLK 1  and CLK 2 , and the number of pins of the serial interface  150  and  250  for particular needs. As the clock signal CLK 1  and CLK 2  are set at a higher clock rate, the number of parallel signals that can be represented by one serial signal in one pin increases, and therefore fewer pins are required in serial interface  150  and  250  for representing parallel signals from parallel interface  110  and  210 , and more space can be saved. Yet extreme high clock rate may cause electromagnetic interference among electrical circuits and is to be avoided for practical reasons. Therefore, setting CLK 1  and CLK 2  at a moderate high clock rate will bring the benefits of reduced size of PDA interface without causing electrical problems. As an improvement of the present embodiment, for example, the above-mentioned 50 MHz clock rate for the first converter  130  and the second converter  230  can be reduced to 25 MHz if, instead of sampling one parallel signals in one cycle of CLK 1  in FIG. 4 a , we allow two parallel signals to be sampled in one cycle of CLK 1 , one at the rising edge of the clock signal CLK 1  and the other at the falling edge. In this way, the converter clock rate is reduced to half of its previous value and the parallel signals are represented by same number of serial signals, thereby greatly alleviating electromagnetic interference that might be caused due to too high a converter clock rate.  
         [0030]    In another embodiment, the inventive PDA  100  can also connect to a desktop computer  30 , as illustrated in FIG. 5, through a cradle  201  using the same connector  106  that is used for connecting to the jacket  200 . By combining two separate interfaces into one, further reduction of physical size of the interface for external connection is accomplished. This is made possible by introducing a switch mechanism between the parallel signals and RS-232 signals. FIG. 6 is a schematic diagram for another embodiment of the present invention. According to the embodiment, parallel signals  120  are bidirectionally converted into serial signals  140  in the same way described above. The serial signals  140  are not to be connected to the cradle straightforwardly, but are directed to first port  172  of a switch unit  170  whose second port  174  receives RS- 232  signals from internal circuitry of the PDA  100 . The switch unit  170  has a third port  176  connected to a nine-pined interface  150 ′ that is to connect to corresponding nine-pined interface  250 ′ on the side of the cradle  201  for signal transfer. The switch unit  170  comprises simple logic circuits that allow the third port  176  to electrically connect to either the first port  172  or the second port  174  according to a selecting signal SEL. When the third port  176  is connected to the first port  172 , the interface  150 ′ can be used for signal transfer between the PDA  100  and the jacket  200 . In such case, although the interface  150 ′ includes nine pins and the serial signals  140  only needs eight pins for transmission, the problem can be resolved by defining one pin of the interface  150 ′ to be unassigned or reserved when the first port  172  and the third port  176  are connected. Some adjustments on the interface  250  of the jacket  200 , which includes only eight pins, would also be required to make it physically connectable to the interface  150 ′.  
         [0031]    On the other hand, when the third port  176  connects to the second port  174  responsive to the selecting signal SEL, RS- 232  signals  160  can be transmitted through the third port  176  and the interface  150 ′ directly to the interface  250 ′ of the cradle  201 . With the help of the cradle  201  connected to the desktop computer  30  using RS- 232  cable  280 , the PDA  100  is able to transfer data with the desktop computer  30  and perform tasks following RS-232 standard. By making the third port  176  switchable between connecting to the first port  172  for transmitting parallel signals  120  and connecting to the second port for transmitting serial signals  160 , the PDA  100  is capable of information transfer with the jacket  200  and the docking cradle  201  using the same interface  150 ′, which is advantageous over prior art where the parallel signals and serial signals are separately transferred through separate connectors. The prior art requires at least 68 pins for PCMCIA transmission plus 9 pins for RS-232 transmission. But in the present invention, the inventive PDA  100  requires only 9 pins plus additional GND and Vcc pins for both PCMCIA transmission and RS-232 transmission. The reduction of pins is tremendous.  
         [0032]    The selecting signal SEL can be issued from a dedicated button on the PDA  100  when depressed by the user attempting to change connection to either the jacket  200  or the cradle  201 . A more convenient and user-friendly implementation is to incorporate a detecting unit  180  to the PDA  100  for automatically generating the selecting signal SEL without control of the user&#39;s hand. The detecting unit  180  detects and monitors the connection of the PDA  100  with either the jacket  200  or the cradle  201 . When the PDA  100  makes connection with the jacket  200  via the interface  150 ′,  250 , the connection event will be detected by the detecting unit  180 . Subsequently the selecting signal SEL is generated and causes the switch unit  170  to have the third port  176  connect to the first port  172  so that parallel signal transfer between the PDA  100 , the jacket  200 , and the expansion card  300  is made possible. On the other hand, when the PDA  100  makes connection with the cradle  201  via the interface  150 ′,  250 ′, the selecting signal SEL generated by the detecting unit  180  will cause the switch unit  170  to have the third port  176  connect to the second port  174  so that serial signal transfer between the PDA  100 , the cradle  201 , and the desktop computer  30  can be effected. By the detecting unit  180 , the PDA  180  can auto-detect which device is being connected to the interface  150 ′, and switch to the corresponding signal transfer mode.  
         [0033]    There are many ways to implement the function of the detecting unit  180 . For example, a light sensible device can be attached to appropriate section of the PDA  100  for determining the presence of the jacket  200 . When the PDA  100  and the jacket  200  are connected, the device senses the presence of the jacket  200  and issues a signal to the switch unit  170  to have the parallel signal transfer mode switched on. But when the PDA  100  and the jacket  200  are disconnected, the absence of the jacket  200  causes no signal to be issued by the light sensible device and the parallel signal transfer mode is not effected, so that the PDA  100  can transfer serial signals with the cradle  201  as default. Another example is to assign a particular pin of the interface  150 ′ as the detecting unit  180 . The detecting pin is characterized by that when it is the jacket  200  that is connected its voltage level is brought high, and when it is the docking cradle  201  that is connected its voltage level is brought low. When the voltage level is high, the parallel signal transfer mode is switched on, and when the voltage level is low, the serial signal transfer mode is switched on. This also gives the PDA  100  an auto-detection function.  
         [0034]    One further advantage of the present invention is that the first interface converter  130  and the switch unit  170  can be built into a switchable interface module that can be easily and flexibly incorporated into existing PDA hardware circuitry in which the parallel signals  120  and serial signals  160  are generated. The modularization of the switch circuitry saves time and cost for PDA manufacturers, for all that needs to be done in providing a switchable interface to a PDA is to direct the parallel signals of the PDA to the converter part of the switchable module, and to direct the serial signals to the second port of the switch unit part of the module. It is also possible to combine the connector interface  150 ′ and the detecting unit  180  as part of the switchable interface module.  
         [0035]    It is to be noted, as can be easily realized by one skilled in the art, that although the jacket serves as communicational bridge between expansion card and the PDA, the jacket itself can be designed to allow the PDA to perform certain added functions without having the expansion card slotted in. In other words, the jacket is itself an expansion module for certain functions just as the expansion card is. For example, the jacket  200  can have a built-in module or circuitry for RF transmission that provides the PDA  100  wireless communication capability. In such case the jacket and the expansion card are integrated into one device.  
         [0036]    Having described the applicant&#39;s invention, it should be noted by the examiner that the description presented above is for disclosure only, not in any sense limiting the scope of the invention. Small modification or juxtaposition of functional elements or their equivalent substitution or replacement can be easily anticipated in accordance with the spirit of the invention by those skilled in the art. All these alternatives are construed as within the scope of the invention. The extent to which the scope of the present invention covers is defined in the following claims.