I was wondering if there is a way to just read data from an existing modbus with an arduino and how I could do it? The arduino would essentially just sit there passively reading the data, it would not need to send any messages. Something like this is what i was thinking..
Would a possible way to be just wire it be like this?
The blue and grey lines go to the respective modbus lines. Would this work? Any help appreciated. Thanks!
Yes and no. The Arduino would not be directly connected to the Data A/B lines. The RS-485 converter would be connected between the Data A/B lines and the serial port. It will be most effective to use an Arduino with two hardware serial ports; one for programming and to send data to the serial monitor and the other to connect to the RS-485 converter. Once you have that establish you will need to modify a slave library to receive and process all telegrams independent of the target node ID, then have it re-transmit the telegram to the serial monitor so that you may read it.
Great thank you very much. And then I'll just opt to use the Arduino MEGA 2560, seems like it has plenty of serial ports.
