I think you are the best shot of solving my interesting problem. I have my laptop in my car, its running on laptop battery power. it has no external powersource in car. Laptop has USB cable thats connected to hondata S300 ECU. I have microphone connected to normal 3,5mm line in jack.
When I turn laptop on, it regognizes microphone nicely and when i turn on ignition, it regognizes the ECU aswell.
Homewher, when I start the car laptop loses ECU, i can't datalog anything with having microphone installed. windows xp just says unregonized device and device not usable..
when i disconnected the mic from laptop, it finds ecu again and datalog works when engine is running. this has something to do with two different power supplies for car and and grounding spots for them...
i'm looking solutions to solve this problem, I believe S300 ecu is made so that when ignition is switched on, its using one or two grouding spots for sensors etc and when its turned on, its using the same ones plus one extra grouding spot. ground voltages may differ here..
also when datalog is turned on, i believe laptop is sending power to datalogging unit inside ECU and I believe also, that its grounded for laptop.
so solution is probably in grounding spots but this is totally new for me, would anynone of you ran into this kind of problem before and would figure easy way to solve this problem?
currently i'm thinking of breaking the microphones 3,5mm connector and take its grounding vire to S300 usb cable, would this idea work? or could it fry something in my car. ?
other option i been thinking is to get usb adapter, that splits the one usb into two different ones as I believe, that those adapters share grounding .. i'm i right or wrong?