MODBUS connection problems

[UnborN]

Hello .. you can follow the recommendations in this thread
that a similar RPi Hat is being used.

sudo raspi-config
goto '5 Interfacing Options'
goto 'P6 Serial'
'Would you like a login shell to be accessible over serial?' --> NO
'Would you like the serial port hardware to be enabled?' --> YES
Finish raspi-config
reboot the Raspberry Pi

@blunoz

I can read the device registers fine with a USB dongle and Windows

as a test. Can you read with the USB to RS485 dongle on the RPi ? (instead of Windows)