Testing MODBUS Communications:

At APRS World, we use a program called Modbus Test Pro by Rogue Engineering for testing MODBUS communications with the 9XTendGateway. Here is a screen shot of communicating with a 9XTendGateway with MODBUS address 1. We are querying 16 analog voltage registers, 40036 through 40067. The results are shown on the middle of the right column.