- Published in issue 12/1995 on page 48
Electrically isolated I²C bus
A deadlock situation occurs if you try to use two optocouplers to isolate two devices connected on an I²C bus. Everything will be fine with the first optocoupler, which will simply convey a 'low' level (logic 0) of the relevant signal (SCL or SDA). The secend optocoupler, however, has its input connected to the output of the first, and will also convey the '0', but, alas, back again to the first! This creates a loop In which the 0 will circle ad infinitum.