Arduino + WattNode Modbus

Hi All,

I'm getting my hands on an Arduino Uno and a WattNode Modbus later this week. I'm rather new to both, but think I can find my way through. I've tried doing some reading on the Arduino with modbus but am not having a ton of luck finding in depth writeups. I know there are modbus libraries available for the Arduino, but is that all I need? How about an RS485 shield? I'm assuming that is necessary to communicate with the Modbus wattnode?

Thanks in advance!


The 485 sheeld, or a 485 interface chip should take care of the hardware side.

I don't know about the software & protocol side, but if there's a Modbus library, that should do it.

There will be settings for baud rate (and maybe some other stuff), and you'll have to make sure the Arduino and the device are both using the same settings. I assume that's all covered in the WattNode user manual.


Wattmode product seems to be a modbus slave, that means you’ll need to have an Arduino modbus master application to communicate with it.
Take care about the data format:
Arduino default serial format is 8 bits, no parity, one stop bit

My previous message was not finished.

Arduino defaut serial data format is 8 bits, no parity, 1 stop bit and standard Arduino Serial library does not allow to modify it.
Modbus defaut serial data format is 8 bits, even parity and 1 stop bit. If the modbus device allows to select no parity, then 2 stop bis are required ( if product is conform to Modbus specification).

This is not really an issue but you have to be aware of that.

Hope this will help