Hi guys,
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.
It's a nice picture - but what is it trying to show?
You can't simply connect two devices to an Arduino Rx pin because Serial idles HIGH and they will interfere with each other. You need diodes to keep them separate.
Also, how can you ensure that only one of the devices talks at any one moment?
The simplest option (assuming you are using an Uno) is probably to use SoftwareSerial to create an extra serial port.
If none of that makes sense please provide more info about what you are trying to do.
I am guessing you are using the current loop interface, since you have an opto-isolator in the diagram. If one of the two wires from either machine is reversed, you will get the description you described.
