I am working on a Projekt where I hook up an Arduino as Vending machine controller to a coin validator and a bill acceptor.
So when I only connect the coin changer everything is working fine, but if I also connect the bill validator I get no more signals from the devices not even the coin changer.
So my guess was that the pull up resistor value is wrong, so I testet 220 ohms, 1k 10k and 100k but nothing worked. Or is my guess completely wrong, what could cause this?
I hook up the devices via a y-cable so TX and rx lines just got split. I use the coinco guardian xl and the coinco vantage.