RS485 PID to PC

Projects General Guidance
1

Hey guys,

I'm trying to find some information on how to obtain RS485 data from a PID and report it to a PC over serial. I have an Omega CN730 PID capable of RS485 communication, ad on the other end I have a dfrobot RS485 shield plugged into an arduino Uno.

RS485 Shield:

CN730 Omega PID

I've got + and - from the RS485 terminals on the PID connected to the + and - pins on the shield respectively. The arduino is the connected to PC over usb. Baud rates are both set at 9600. I was hoping I'd be able to go into the serial monitor with some if(Serial.available()) code and get a readout there to start but haven't had any luck yet.

I feel like there's something obvious I'm missing here but maybe I'm way off. Any help is huge.

Thanks

2

You have to use MODBUSR protocol in communication with the PID. See pg. 16 ff. in the user manual.

3

Attention, this device communicates in ModBus ASCII. I'm not aware of a library for ModBus ASCII on the Arduino platform. It might be not too difficult to adapt a ModBus RTU library to send and receive in ASCII but depending on the used library the changes might be substantial.