Modbus error CRC

[CristianAgata]

Hi everybody,
I've this error (see attached file) on a modbus system.
Any suggest?

[admin]

This usually means there's a problem on the physical bus level.
Make sure that parity and stop bits settings are correct. Check if GND is connected between LM and the Modbus device. A termination resistor might be needed as well. Also check AC polarity on both LM and the Modbus device. There was a report where one of the power supplies has AC polarity connected in reverse and this caused communication issues.