I have a HomeAutomation project which uses the MCP23017 chip but sometimes this locks up and only thing that helps is to reset the Arduino.
I have designed a IO expander board that contains 2 chips. All inputs are opto isolated (earlier I experienced disturbances on the inputs causing the outputs going nuts).
The problem I have is that for some reason one of the chips freezes and at the same time it changes the status of the outputs for the freezed chip to 0.
Can anyone see anything obvious in my schematic for the IO card?
The HomeAutomation project can be found here: http://forum.arduino.cc/index.php?topic=260708.0