Hardware connection

Software configuration

Modbus test
RTU Modbus
00 03 00 00 00 01 85 DB
00 03 00 01 00 01 D4 1B
00 03 00 00 00 02 85 DB
TCP Modbus
01 07 00 00 00 06 00 03 00 00 00 01
01 07 00 00 00 06 00 03 00 01 00 01
01 07 00 00 00 06 00 03 00 00 00 02

MQTT

Best wish!