Different outside temperatures?

[Bartb]

Hi,

In my otmonitor log I find the following messages:
17:12:50.759813 T001B0000 Read-Data Outside temperature (MsgID=27): 0.00
17:12:50.901071 B401BFF1A Read-Ack Outside temperature (MsgID=27): -0.90
17:12:50.928116 A401BFF34 Read-Ack Outside temperature (MsgID=27): -0.80

I have read that the B message comes from the Boiler, the T message comes from the thermostat and the A message is a response returned to the thermostat. (Coming from where?)
The value in the B message makes most sense; it's the temp reported by the outside temperature sensor, which is connected to my boiler (Remeha Tzerra Ace)
The value in the A message is 0.1 degrees lower (0.. Where does this value come from?
The T message is 0, while my Nefit Easy thermostat (incl Easy Connect adapter for OT) shows -2.0 degrees as outside temp on the app.
I presume it gets it from Nefit/Bosch, from the internet somewhere ... Regardless... it's just wrong.

Questions:
- Why is there a difference in the B and A message values? Or where does the 0.8 come from?
- Does the -2 degrees on the Nefit app mean that this is the outside temp used to calculate/set the CH water temp, instead of the 0,9 degrees measured by my own outside temp sensor?

Thanks.

[hvxl]

The T message is a Read-Data request. So the thermostat is asking for the temperature, not providing it. The data in such a message is meaningless and should normally be 0. The A message is the response returned to the thermostat by the OTGW. It will replace the data received from the boiler if either an OT command hes been performed, or a temperature sensor is attached to the OTGW and GPIO B is configured to read the sensor (and TS is set to 'O', the default).

I have no idea which outside temperature the Nefit Easy uses, if any.