Help with Modbus 485 network and Digione IAP

Digi One IA/IAP
1

I’ve purchased two digione IAPs to talk to CAT engines over a 485 network. I can’t seem to get the IAP to communicate over 485 2 wire.

I’ve tested everything with modscan32 and a USB-485 converter and I can communicate fine. I’ve matched the communication settings, and I have the terminal switch (4) in the up position.

I’ve done the telnet scan and I show “no response or timeout”. I’m using the industrial protocol. I’m using Mobus TCP master to Modbus RTU slave. I’m trying to communicate with modscan32.

Both the ethernet and serial lights are blinking. The IAP doesn’t seem to communicate with the 485 device.

Any ideas? I’ve used the IAP for modbus TCP to Ethernet/IP before. This is the first time I’ve used it on a 485 network.

These are my table settings:

table=1 name=table
table=1 route=1 protocol=modbusrtu protaddr=0-255 type=serial port=1
table=1 route=1 active=on

Network Sources (Masters):
master=1 protocol=modbustcp table=1 transport=tcp ipport=502 chartimeout=50ms
master=1 messagetimeout=2500ms idletimeout=5min permit=all priority=medium
master=1 active=on

Serial Sources/Destinations (Masters/Slaves):
serial=1 protocol=modbusrtu type=slave table=1 messagetimeout=2500ms
serial=1 slavetimeout=1sec chartimeout=20ms
serial=1 broadcast=off
serial=2 protocol=modbusrtu type=slave table=1 messagetimeout=2500ms
serial=2 slavetimeout=1sec chartimeout=20ms

2

It is probably wiring - usually is. RS-485 can be a royal pain to wire up because the original spec defined the terminals in a virtual 100% guarrenteed to be a problem way.

How have you wired the system? You understand the problems with RS-485 naming, how one vendor’s “A” might be another vendor’s “B”.