I'm new to Arduino but having really good results so far..
I'm using Arduino ADK to interface with my car electronics (ISIS). The Arduino is controlled by an Android Tablet or Smartphone. I'm using the ISIS Power intelligent multiplex system on the back end. http://www.isispower.com/
The ISIS MasterCell or controller is basically a PIC microcontroller. The Arduino digital output pins are connected to the ISIS controller (MasterCell) digital input pins.
It goes something like this..
Android Tablet --> wireless --> AP --> Arduino ADK w/Eth (digital out) --> MasterCell input --> CAN BUS --> PowerCell --> +12v to lights, pumps, fans, etc..
The ISIS controller requires a logic low on the input pins to turn on an output (+12v) of the PowerCell. I configured the Arduino output pins to be HIGH at startup (void setup) for the (Switch OFF) position. When I want to activate the function I digitalWhite(pin, LOW) to provide the LOW that ISIS needs to turn on the output. This is all working fine except for an unexpected feature on the Arduino. If I remove power to the Arduino board, it takes all the output pins low and turns on all the outputs of the ISIS. I guess I expected the Arduino output pins to go to a high impedance state when power was removed but that doesn't appear to be how it works.
The possible solution I'm considering is to add Hex inverters between the Arduino and the ISIS controller and change the Arduino output logic to be LOW for the off function and HIGH for the on function. Is this my best option? If so, any recommendation for the inverter chip? I'm considering the MC74F04N as I have those readily available.
Thanks in advance!!