Arduino ModBus RTU master communication with Power Meter problem
I have made it. Now it is working. I only checks A &amp; B cables (tried a new one) and change address of register from 5000 to 0x5000 and now it works. I thought that this library already give 0x before address, because i didn't see it anywhere with 0x before.
An advice for people with the same problems:
Most of the devices which is using RS485 and ModBus protocol (and have an some kind of display) shows an communication (over 485 &amp; modbus) on display by some kind of mark, for example in my case it was an &quot;dot&quot; which blinks when there's an communication. When this mark is shown, it is sign of that the communication settings is right, so data, parity bit, stop bit &amp; baudrate is OK (data has successfully reached the dest. device).
After that, these devices send you an error message back on its line. So if you have problems with getting data, you should send your message (ask) from the arduino to that device, over an Transmit pin from arduino (of course trough an converter, for example max485) and the Receiving pin (side) connect to your PC through again some kind of converter from UART to USB. (Warning: you should have the same ground potential, so wire all grounds together)
Install some software to communication for modBus on PC (i am using this soft: https://www.simplymodbus.ca/ | you can use demo ) After that let arduino sent an message and receive it by PC. (in simplymodbus look at the &quot;response&quot;) read that code and look to the manual for the device you using, where there should be an description of error codes, if not look at this doc.: http://www.simplymodbus.ca/exceptions.htm or THIS).After that you will have an better look on what is going on and where there is a problem.