Opentherm Gateway 4.0 alpha/beta testers wanted

[Templar]

Unfortunately I have not been able to get my hands on the actual specification, so I have to fill in some blanks by trying, guessing and observing.

I found additional Smartpower specs at this location:
http://www.opentherm.eu/product/view/6/toon
It looks like they're adding new devices with their specs.

ID2:HB0: Master configuration: Smart power

[hvxl]

Interesting, but not really what I would call a specification.

My current understanding is that ID2:HB0 indicates that the thermostat would like to be able to use smart power at some point in the future. I presume the boiler will clear this bit in its response if it doesn't support the feature. To actually switch to a higher power level, the thermostat makes the line high for some amount of time. A high level for 10ms seems to signify a switch from low->medium power. And I see a high level of 15ms for a medium->low power switch. The thermostat will need to keep the line at the logical 1 level for high power.

What I would like to know are the exact allowed timings. Is anything below 12.5ms low->medium? And after how much time should the gateway conclude that a line that remains high means low->high, rather than low->medium? Is the duration of the high level actually significant or is any high level of around 10-15ms simply a switch between low and medium power levels?

[steelrv]

@hvxl

I would like to have some extra CMDs in the OTG firmware.

They are not difficult but will help me a lot.

1. CMD to reset /reboot the OTG print. In this way it can start from scratch with configuring parameters.

2. CMD to retrieve the following statusses
At least:
- Flame is on
- Central heating is on
- Hot water is on
Nice to have:
- Comfort mode (Domestic Hot Water Enable) is on
- Boiler requires maintenance
I know the above statusses are available on the LED outputs, but I would like to have them in my domotica system.
Reason to have the first three items is that I would like to control my floor pump downstairs. If the CV pump is on I would like to turn on the pump downstairs. If the CV pump is off I would like to turn off the pump downstairs.

Hope you can add this extra functionality! Ofcourse I will beta-test it.

[Rene]

These signals are already availabe when your boiler supports this, e.g. central heating on: ch_enable, domestic hot water on: dhw_active (message 0x00).

[hvxl]

As Rene mentioned, you can get all the information you request already by looking at the opentherm messages the gateway reports:

- Flame is on = ID0:LB3
- Central heating is on = ID0:LB1
- Hot water is on = ID0:LB2
- Comfort mode is on = ID0:HB1
- Boiler requires maintenance = ID0:LB6

Since the low byte is filled in by the boiler, you have to look at the response for the LBX bits. In the request those bits will always be 0.

[steelrv]

@Rene & hvxl,

thnx for the fast replies.. will use the message you suggested!

hvxl, what about my first request? the CMD to reboot/reset the OTG print? Is that possible in a future release?

[hvxl]

You can send a BREAK condition on the serial line. That's pretty close to a reset.

[Templar]

Interesting, but not really what I would call a specification.

My current understanding is that ID2:HB0 indicates that the thermostat would like to be able to use smart power at some point in the future. I presume the boiler will clear this bit in its response if it doesn't support the feature. To actually switch to a higher power level, the thermostat makes the line high for some amount of time. A high level for 10ms seems to signify a switch from low->medium power. And I see a high level of 15ms for a medium->low power switch. The thermostat will need to keep the line at the logical 1 level for high power.

What I would like to know are the exact allowed timings. Is anything below 12.5ms low->medium? And after how much time should the gateway conclude that a line that remains high means low->high, rather than low->medium? Is the duration of the high level actually significant or is any high level of around 10-15ms simply a switch between low and medium power levels?

Are the timings in this table any good? They are allowed Smartpower settings used with the OpenTherm TestTool.

Honeywell Functional specification OpenTherm TestTool V2.4

OT Smartpower settings.png (73.37 KiB) Viewed 7353 times

[hvxl]

That was one puzzle-piece I used to be able to come up with something that had a chance of handling smart power. From that starting point it still took a lot of experimentation to actually make it work.

But thanks for keeping your eyes open for any shred of information on this subject.

[hvxl]

I have just published firmware version 4.0a6 on my Alpha/Beta firmware page. This firmware has experimental support for Smart Power. I have tested it with a Remeha iSense thermostat, but would love to hear how it works with other Smart Power equipment.

The firmware has other new features for the Remeha iSense as well. It should now be much better at controlling the setpoint via the Opentherm interface.

There are new features for people who had the good sense (or good fortune) to buy a different thermostat too. The gateway now has a number of built-in functions that can be assigned to the GPIO pins. This firmware is also much less sensitive about bit timings that do not meet the opentherm specifications, which should be good News for owners of an Intergas boiler.

For more details, see the new features listed on the Alpha/Beta firmware page.

[Templar]

I have just published firmware version 4.0a6 on my Alpha/Beta firmware page. This firmware has experimental support for Smart Power. I have tested it with a Remeha iSense thermostat, but would love to hear how it works with other Smart Power equipment.

Nice to see it has experimental SmartPower support. No hardware changes were required to support medium/high power?

[fabian]

A bit offtopic, should i be able to use a remeha isense with my intergas boiler ?

My honeywell modulation is hard to read in the dark

[hvxl]

Nice to see it has experimental SmartPower support. No hardware changes were required to support medium/high power?

No. To my own pleasant surprise, it appears to be possible to support Smart Power with the existing circuit design.

[hvxl]

A bit offtopic, should i be able to use a remeha isense with my intergas boiler ?

My honeywell modulation is hard to read in the dark

Yes, the most crummy thermostat I know with the most crummy boiler (opentherm-wise) should actually work pretty well now with the gateway in between.

My honeywell modulation does have screen backlight, but it can't keep that up nearly as long as a Smart-Powered iSense.

[Templar]

I happen to have an Intergas Kombi Kompakt HR22 boiler, but I cannot remember communication problems with the OTGW or the Honeywell Vision Thermostat. Do all Intergas boilers have timing problem?