blink.nxc

#define I2Cport S1       // Port number
#define I2CAddr8574 0x70 // I2C address x040 8574 or 0x70 for 8574A
byte WriteBuf[]={I2CAddr8574,0x00}; // write buffer is addr and data

task main() {
  int nbytes;
  SetSensorLowspeed (I2Cport);       // Configure I2C port
  while (true) {
    WriteBuf[1]++;                   // update data byte
    I2CWrite(I2Cport, 0, WriteBuf);  // send buffer
    while(I2CStatus(I2Cport, nbytes)==STAT_COMM_PENDING); // wait
  }
}