Modbus RTU - overlay with RS485 converter

For Lan Controller HW 3.7, 3.8

It allows convenient connection to the Modbus RTU bus, also outputs a serial port and 3.3V power supply (does not block the serial port, uses free GPIO).

Currently, the Lan Controller supports the following devices on the Modbus RTU bus:

• Eastron SDM72 and SDM120M energy meters.
• Water parameter sensor RDO-PRO-X.