Readout roomtemperature and setpoint from opentherm thermostat

Projects Programming
1

Hello,

I want to readout the room temperature and setpoint temperature from a modulating thermostat with opentherm. I can readout the information. Unfortunately the frequency of the information is very low.
Messages are only once a second, and message ID 24 with roomtemperature is only comming about once a minute. Just like the message ID 16 which is holding the room temperature setpoint.

Is there a way to get the room tempearture and setpoint more frequently?

I bought this 'opentherm slave shield' and connected in to my arduino uno

Connections:
Arduino 3.3 V to 3.3V board
Arduino 5V to 5V board
Arduino GND to GND board
Arduino Digital 2 to D2 board
Arduino Digital 3 to D1 board

I used this code:

Now I have it working and below some serialdump:
14:06:26.073 -> message.id 5 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:27.044 -> message.id 25 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:28.062 -> message.id 1 , message.type 5 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:29.052 -> message.id 0 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:30.041 -> message.id 17 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:31.033 -> message.id 9 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:32.023 -> message.id 14 , message.type 5 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:33.010 -> message.id 25 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:34.019 -> message.id 1 , message.type 5 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:35.011 -> message.id 0 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:35.999 -> message.id 17 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:36.968 -> message.id 9 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:37.941 -> message.id 16 , message.type 5 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:38.954 -> message.id 25 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:39.956 -> message.id 1 , message.type 5 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:40.956 -> message.id 0 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:41.940 -> message.id 17 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:42.939 -> message.id 9 , message.type 4 , Roomtemp: 20.55 ,RTsetpointT: 19.00
14:06:43.942 -> message.id 24 , message.type 5 , Roomtemp: 20.60 ,RTsetpointT: 19.00
14:06:44.888 -> message.id 25 , message.type 4 , Roomtemp: 20.60 ,RTsetpointT: 19.00
14:06:45.906 -> message.id 1 , message.type 5 , Roomtemp: 20.60 ,RTsetpointT: 19.00
14:06:46.873 -> message.id 0 , message.type 4 , Roomtemp: 20.60 ,RTsetpointT: 19.00
14:06:47.896 -> message.id 17 , message.type 4 , Roomtemp: 20.60 ,RTsetpointT: 19.00

Kind regards!

2

Wouldn't that be fast enough to monitor a slow system like room temperature?
Basically you should convince your thermostat to send more messages... might be pretty troublesome without a protocol and might even be impossible if the update interval is 'baked in' the thermostat code as a constant...

3

By the way: interesting that you were able to read the data this way.
Doe you also receive info from the heating system? Like water pressure too low? Tap water used?

4

The 'heating system' is the arduino board. I want to use the information to control my heatpump.
Indeed maybe it is fast enough, but I would like a bit more speed if it is possible :slight_smile:

5

Ok, then the heating system is the heat pump...

6

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