What is Modbus-RTU?
Modbus is a serial communication protocol that enables communication among different devices connected to the same network.
Modbus-RTU refers to Modbus in an RS485 BUS
A RS485 BUS consists to 2 wires, positive and negative (+ ground), which connects all your meters (Slaves) to the gateway (Master)
To configure a Modbus-RTU Network:
- Slave Address: Unique in all devices in the RS-485 BUS
- Baudrate: same in all devices in the RS-485 BUS (9600, 19200, etc)
- Parity: same in all devices in the RS-485 BUS (Usually = none)
- Data Bits: same in all devices in the RS-485 BUS (Usually = 8)
- Stop Bits: same in all devices in the RS-485 BUS (Usually = 1)
What is Modbus-TCP?
Simply put, this is a Modbus RTU message transmitted with a TCP/IP wrapper and sent over a network instead of serial lines.
The Server does not have a SlaveID since it uses an IP Address instead.
To configure a Modbus-TCP Network:
- One or several RS485 BUS behind Modbus TCP bridges
- Slave Address (Unique in all devices in each RS485 BUS)
- IP/PORT of the Modbus Bridge
Example of Modbus configuration in DEXGate2:
In DEXGate2, you can use both Modbus-RTU and Modbus-TCP at the same time.
Modbus-RTU devices will be configured using the baudrate and Slave address (Green text at the example)
Modbus-TCP devices will be configured using the Modbus-TCP Bridge IP and port and the Slave address (Blue text at the example)
Connecting a RS485 cable
Modbus configuration in DEXGate2 (User manual)