Opentherm Gateway assembly problem

[k_delaat]

I have build the OTG myself on a breadboard. Everything is working fine except two problems.

1. Now and then the message Thermostat disconnected appaers.
2. The backlight of my Honeywell Vision Modulation is flashing after connecting the OTG. If I disconnect the boiler it will stop flashing (but also stop functioning).

I think at least problem 2 has something to do with lowering the voltage of the thermostat if a message is send to the thermostat.

Are these problems known to someone or has someone a solution?

[hvxl]

I suspect this is due to the smart power feature. I don't have any details on this feature, so I don't know if it is negotiated via opentherm messages or via electrical properties. In any case, the opentherm gateway doesn't support it.

The symptoms you describe seem to suggest that opentherm messages are involved. When the thermostat wants to switch on its backlight, it would request to use a higher power level. The gateway doesn't understand this message and simply passes it on to the boiler. The boiler responds that it accepts the power level change. The thermostat then starts to use higher voltages for both the logical low and high levels. Since the gateway is oblivious about the smart power stuff, it suddenly only sees high levels from the thermostat. It is unable to distinguish that from a disconnected thermostat, so that's what it reports. After some timeout of being unable to communicate, both the thermostat and boiler fall back to regular power levels and the whole thing starts from the top, resulting in the flashing you see. Or at least, that is my speculation.

I would love to see a trace from such a situation. Hopefully I can at least figure out which opentherm message is used for the smart power negotiations. Then I can make the gateway reply to such messages with Unknown-DataID, preventing the problem. Obviously, without full smart power support in the gateway, your thermostat will not be able to switch on its backlight any time it wants.

[Templar]

I've got a Honeywell Vision Modulation thermostat too. As far as I know it is not Smartpower enabled. If I am not misstaken, the thermostat has a small battery/capacitor for backlight use.

[k_delaat]

I've got a Honeywell Vision Modulation thermostat too. As far as I know it is not Smartpower enabled. If I am not misstaken, the thermostat has a small battery/capacitor for backlight use.

That battery is also in the manual. According to the manual the date and time is preserved. But this is also not the case for me. I bougth my thermostat via Marktplaats, so that won't be fixed under waranty.

But I don't think the problem is in this battery. As I connect the thermostat directly to the boiler there is no problem with the backlight.

[k_delaat]

I made a small movie of the thermostat, maybe this helps understanding the problem

http://dl.dropbox.com/u/34012/VID_20121211_224341.mp4

[Templar]

According to the manual the date and time is preserved. But this is also not the case for me.

For me neither, and I bought mine brand new. I guess we found the first Vision Modulation bug?

[hvxl]

I made a small movie of the thermostat

Interesting video, but not quite what I meant by a trace. Can you please start otmonitor and go to File->Save to logfile, specify a file name and click Save. Then do the same action that caused the flashing again and close otmonitor (to make sure all data is flushed to the file). You can post the file somewhere or send it to me. Let me know if you need my email address and I will send it via a PM.

[k_delaat]

Hereby a logfile of OTMonitor. I activated the backlight of my thermostat. I don't see any message in this log relating to the backlight, so I think it's in the hardware.

[hvxl]

I don't see any message in this log relating to the backlight

Indeed, no clues in there. I am currently out of ideas then.

[k_delaat]

I just soldered everything onto the PCB (which I yesterday received from Lennart). But the problem of a flashing backlight still remains. Is there maybe something wrong with my components?
Before soldering everything to the board I measered all resistors, so I'm sure they are all correct.