I then outputs via I2C a HIGH (value 0 - different to Arduino) to turn ON the LED. If the above statement seemed a bit odd, remember that the PCF8574 will SINK the current, not source it, so we have ...

#define GroveDigitalExtender_SENSEHIGH_ADDR (0x06) // Interrupt direction 7-4 #define GroveDigitalExtender_SENSELOW_ADDR (0x07) // Interrupt direction 3-0 #define ...