MODBUS

[ace2light]

Hi 

I am currently working with a meter that collects reading of power and rpm, named TERCO N30O and N30B. They are wired together into a single device, however, their unit ID for these 2 meters are different. I am trying to read datas using MODBUS. Is there a way to read datas from 2 different unit ID in a single modbus read holding register? 

Thanks in advance! 

[RavensFan · Accepted solution]

Of course there is.

First question is what Modbus library are you using? 

For the older modbus library, you open the serial connection and when you do your Read holding register, you use the slave address for the one device and read the register, then use the slave address for the other device and read the register.

The newer libraries, (purple or yellow header based on classes) you create two different modbus instances and use the Set Unit ID function to change the Unit ID on each class wire before calling the Read holding register.

[ace2light]

Thank you!