Modbus RTU behavior

[JohnTH]

Hi,
When I run read test from device I get correct result. 

   

When I try with this profile:

{
  "manufacturer": "Kamstrup",
  "description": "Fjernvarme modbus",
  "mapping": [
    { "name": "Heat_Energy", "bus_datatype": "float32", "type": "inputregister", "address": 20, "writable": 0}
  ]
}

I get this error in log:

   

I select rtu2 with default timeout and poll interval. What am I missing?

-John