Hi everyone,
Is there anyone who had any experience about Arduino and Modbus RTU over RS485? I'm doing some basic experiments about ProviewR and Arduino communication through Modbus RTU over RS485 by toggling two LEDs from an XttGraph object (the Arduino is set up as a Modbus RTU slave through /dev/ttyUSB0), but it's not working. So, I want to know what could be wrong, whether in the ProviewR project settings or in the Arduino sketch (I'm using the "ModbusRtu.h" library from github.com/smarmengol/Modbus-Master-Slave-for-Arduino ).
I've added the snapshots and my Arduino sketch as attachments below.

Any help greatly appreciated.

/Maverick

(My setup: ProviewR V5.7 amd64 on Ubuntu Mate 18.04)

Hi Maveric,

Slave id in the sketch is set to 1 so you should set UnitId in the module object to 1.

/Claes

Hi Claes,
Thank you for your answer. I've tried to set up the slave UnitId to 1, but it's not working. I've also tried to set the slave Address to 0, but still not working.
Maybe it's in the Arduino. Well, i'm going to try other Modbus RTU Arduino libraries.

/Maverick

Hi Claes,
After some research, I'm back again. This time, I am using an Arduino Modbus RTU Slave library from codeload.github.com/smarmengol/Modbus-Ma...ip/refs/heads/master
Still not able to toggle these two LED from a XttGraph in Proview, but at least, the good news is that after tweaking the /dev/ttyUSB0 serial port read/write permission settings, I finally managed to establish a working serial connection between Arduino and Proview Runtime monitor. I'm almost there, but it's not over yet... I'm wondering about what could be still wrong in my setup.
I've sent my Arduino sketch (with the Modbus RTU library) and some snapshots below as attachments.

(By the way, I'd like to have some useful advice from Brunad if he's still available and active on the forum)

/Maverick

Hi Maverick,

Another error I can see is that Representation in the ChanDi and ChanDo should be Bit8 for Coils

/Claes

Hi Claes,
Thanks for your answer but changing the ChanDo representation to Bit8 didn't work. Bit16 also didn't work either.

/Maverick