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Troubleshooting of modbus communication to a serial device connected through an EGX100 or EGX300
EGX web server, dip switches, and wiring
Physical wiring, dip switch configuration settings, and the EGX web server configuration must be correct in order for correct communications.
The EGX supports both 2-wire and 4-wire configurations provided dip switch settings are correct and serial port settings match. The EGX installation guide includes details about wiring 2-wire and 4-wire systems. If a 4-wire device needs to be connected to a 2 wire configured EGX, bridge RX+ with TX+ on the device, and connect this to the Rx+ connection on the EGX. Similarly, bridge RX- with TX- on the device, and connect this to the Rx- connection on the EGX.
The EGX dip switch configuration for the RS-485 Biasing and Termination should be set to match the system as described below.
Figure 1: Dip Switch Configuration For 2 or 4-wire Devices
EGX web server configuration
To access the configuration section for the EGX serial port access the EGX web server by typing the IP address into a web browser. Navigate to Setup->Serial Port
Figure 2: Serial port configuration on EGX web server
NOTE: Unit ID is not recommended to be set to 100. The reason being that Unit ID 100 is reserved for Modbus TCP connection.
Verifying Successful Communication
The 3 screen shots below displays what the correct configuration will result in.