Please download the Modbus Test zip file that includes a test program and help graphic for basic testing and connecting of Mi3COMMM and Mi3MCOMMM to verify that the sensor or RS485 adapter is working. Please note that for register 1080 you will need to have 1 head connected and this must have setup as HEAD1.
The Modbus over serial line V1 document may also be useful.
Additionally, the address must be set by the push buttons on the COMM box and not as the Multidrop address as seen in DTMD 5.4.1.
This address can also be checked using the ASCII command via the USB port:
?XAS this is the Modbus address
?XA this is the Multidrop address and must be set to 0 (XA=0)
Using SimplyModbus allows one to see the full frame request. In this example, we are polling the box temperature:
01 04 00 4F 00 02 40 1C
Use this method if you have a box without head - poll register 80
In this example, we are polling target temperature of Head 1. In the orange boxed area you can see the full frame request:
01 04 04 37 00 02 C1 35
Use this method if you have a box with a head connected. Change 1080 to 2080 for Head 2, 3080 for Head 3 etc.
Further example for reading the box baud rate with and without offset:
With -1 offset: