[Tinyos-help] about I2C in tinyos 2.0

[jianxin chen]

Dear all,
     In my system a compass is added to MICAz node by I2C communication mode
in tinyos 2.0.
     Now I want to obtain the compass output periodically.
     The program follows, but I can not obtain the compass output.

In the configuration file
  {
      ......
   Compass.Resource  -> ATM128I2CMasterC.Resource;
   Compass. I2CPacket -> ATM128I2CMasterC.I2CPacket;
   }

 In the main fie we define
 module Compass{
   .....
 Interface Resource;
 Interface  I2CPacket<TI2CBasicAddr>
}

    In the Timer function we request the resource:
    Timer.fire(){
        Resource.request();
        .....
      }
 In the resource granted function we read the compass output by I2C  as
following
    Resource.granted(){
           if(call I2CPacket.write(I2C_START,C0,.....)==SUCCESS)
                 {
                     // delay(100);
                      if(call I2CPacket.write(I2C_START,C1,.....)==SUCCESS)
                        call I2CPacket.read(I2C_START,C1,.....);
                   }
            Resource.release();
       }

     Even I add the delay(100), it still does not  work. When I track the
program, and find the second ``call I2CPacket.write(I2C_START,C1,.....)`` is
not successful.
After careful analysis of the I2C driver, I found in the program
Atm128I2CMasterPacketP.nc, when the I2CPacket.write begins, the variable "
state" changes into
I2C_STARTING.  When this function call I2C.sendCommand() function and
finishes, the variable state still is I2C_STARTING. Track  the
I2C.sendCommand() in the HplAtm128I2CBusP file and found, there is only one
operation TWCR=current.
       It appear weird that there  is no event to change the state variabe
in  Atm128I2CMasterPacketP.nc. It is evident, after the writing operation is
done, there should exist an operation to change the state. But I can not
find  it.
      Does anyone give me help?
      Thanks a lot!

       Jianxin Chen
     .
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