Master inactivity timeout
The module looks by default at the USB port for communications.
When activity is detected on the RS232 or RS485 port, the module switches to look
at the relevant port for further data. If no data activity is detected on the port for the
duration of the master inactivity timer, it reverts to looking at the USB port.
This should be set longer than the time between modbus polls from the master.
Baud rate adjustable
from 1200-115200