I’ve been integrating the first SDCC implementation of an I2C Master module with my current EE project and the results are positive. While this is but a small piece of a much larger puzzle, I’m pleased that I’ve been able to hit the ground running with this compiler. The C implementation is much shorter that the previous assembly language program… and easier to read. Below is the majority of the transaction with the master first sending a “stop ranging” command to the slave, followed by a write requesting the most recent range information. The last half of the transaction is the master read of two bytes of range data in MSB format.

The corrisponding C code is just this simple:

//Enable range sensor and wait
i2cMasterStart(5);
buffer[0] = EnableSensor;
result = i2cMasterWrite(RangeSensorA, (char*)&buffer, 1, 10);
i2cMasterStop(5);

//Measure range for 0.5 seconds at 8MHz
delay1mtcy(1);

if(result == _I2C_OK) {
   //Disable range sensor
   buffer[0] = DisableSensor;
   i2cMasterStart(5);
   result = i2cMasterWrite(RangeSensorA, (char*)&buffer, 1, 10);
   i2cMasterStop(5);

   if(result == _I2C_OK) {
      //Get range
      i2cMasterStart(5);
      buffer[0] = GetLatestRange;
      result = i2cMasterWrite(RangeSensorA, (char*)&buffer, 1, 10);
      if(result == _I2C_OK) {
         i2cMasterRepeatedStart(10);
         result = i2cMasterRead(RangeSensorA, (char*)&buffer, 2, 20);
      } //write result ok
      i2cMasterStop(5);
   }
}

delay1ktcy(100);