OTGW used to simulate a boiler device

This Forum is about the Opentherm gateway (OTG) from Schelte

Moderator: hvxl

OTGW used to simulate a boiler device

Postby warp » Sat Sep 14, 2019 10:45 am

Hi,

I recently bought a thermostat (toon, for testing purpose) that can communicate with a boiler using opentherm protocol.
Unfortunately my boiler is not compatible with opentherm.

I have a RPi that is connected to the boiler using optolink (see https://github.com/openv/openv/wiki/Die ... nittstelle for information ). Almost all commands work.
I can read values, change setpoints, change heating mode...

I was wondering if I could use this OTGW as an intermediate appliance between the thermostat, and the RPi.
So that there would be nothing to change on the thermostat.
Obviously I would need to code the communication between the OTGW and the RPi, but considering the hardware fits to my use case.
Thanks.
warp
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Re: OTGW used to simulate a boiler device

Postby hvxl » Mon Sep 16, 2019 9:26 pm

If you use the interface firmware, you could write some code that will receive an Opentherm message from the thermostat, translate that to the appropriate optolink value, and then generate a response back to the thermostat.

Officially, a slave device should respond within 400 ms. I don't know if that is enough time to actually obtain the requested information over optolink (at 4800 baud) on the spot, or if you have to prefetch information so you can return it immediately without having to send a query over optolink at that moment. You can also decide to relax the requirements and aim for the 800 ms interval, within which the master device must receive an answer.
Schelte
hvxl
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Re: OTGW used to simulate a boiler device

Postby warp » Mon Sep 16, 2019 10:27 pm

So from a physical point of view it can work (with the interface firmware).
I did not think about the protocol timing.

There’s no need to have real-time data. A delay of some seconds is totally acceptable.
Currently everything is cached in Domoticz, so data will be directly available.

...anyway, I think that’s enough to give it a try...
I’ll post again in some ...weeks ?... with my setup description and test results.
Thanks
warp
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