WR31 serial port status indicate a few bytes sent every second

The serial port is configured for RS485 half duplex and modbus master enabled for the port.

The strange thing is the serial port status “Bytes Sent” keeps incrementing by two bytes every second no matter if modbus master enabled or not.

The modbus works over TCP using the master, but receives an error now and then. I was wondering if the extra bytes are involved and where they come from?

The unused serial port port 1 is not used but also counts a few ticks every second.

It appears that the serial port configured for RS485 half duplex is experiencing a consistent increment of two bytes in the “Bytes Sent” status, even when the Modbus master is disabled. Additionally, Modbus over TCP using the master occasionally encounters errors. This issue may be related to the extra bytes incrementing every second. Please check the serial port configurations, ensure proper termination, and review Modbus communication settings to address these issues promptly.