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Communication only in Monitor mode

PostPosted: Mon Oct 12, 2015 2:56 pm
by ilcalmo
I bought the interface kit with all components and I just assembled for myself.
I should not have any USB communication problems since I can change firmware and see diagnostics with diagnostic firmware installed on the PIC
My thermostat is Brahma OT11, my boiler is "Emmeti Althea S - I do not know who is the real brand..."

I read the troubleshooting page and I can see some data (such as room temperature, room setpoint, max ch water setpoint, dhw setpoint) only in monitor mode, but still getting lots of Errors 03 in the log window.

If I power off and power on again the gateway I do not get any connection with thermostat, because the interface starts always in Gateway mode.
The only way to get it connected the the boiler is to launch otmonitor and set the inteface to Monitor mode.

If I download the diagnostic firmware the thermostat connects to the boiler in a very short time, and I can see messages if I make tests.

Some tests I made:

Test 5 with all connected:
Code: Select all
Enter test number: 5
Thermostat: 0.69, 1.02, 2.36
Boiler: 0.00, 1.75, 2.08
Reference: 1.21

Test 6 with all connected:
Code: Select all
B: 177.664
T: 177.759
B: 177.783
T: 178.124
B: 178.150
T: 178.173
B: 178.196
T: 113.636
B: 113.662
T: 113.685
B: 113.708
T: 198.647
B: 198.669
T: 198.692
B: 198.719
T: 132.013
B: 132.036
T: 132.063

Test 4 with loopback:
Code: Select all
Enter test number: 4
OK1A high-to-low: 10us
OK1A low-to-high: 27us
OK1B high-to-low: 5us
OK1B low-to-high: 6us

Test 5 with loopback:
Code: Select all
Enter test number: 5
Thermostat: 2.16
Boiler: 2.37
Reference: 1.21

If I make Test 2 (Bit timing thermostat) i get no errors and I see some data such as Room temperature and so on.
If I make Test 3 (Bit timing Boiler) i get lots of errors 01 and 03 and some time data such as: Boiler water temperature, Relative modulation level, and some others.

Is there anyway to send you the diagnostic window data with labels and red numbers?

Any help or hint to get it working?


Re: Communication only in Monitor mode

PostPosted: Tue Oct 13, 2015 6:00 pm
by hvxl
From your description it sounds like the OTGW has some problems with the signal from the boiler. The output from test 3 would be helpful. It is not a problem if the colors get lost with copy/pasting. The red color only provides a more obvious indication of signals that are too short or too long. I can regenerate that information from the numbers.

Have you tried changing the reference voltage? Looking at the test results I don't expect it will help, but there is a small chance and it's something that you can easily try.

Re: Communication only in Monitor mode

PostPosted: Tue Oct 13, 2015 7:14 pm
by ilcalmo
7-zip file
(12.72 KiB) Downloaded 238 times
Thanks for your prompt reply.

I tried to change reference voltage, but did not solved the problem. Values below 1.042V switch off the thermostat, values over 1,667V also switch off the thermostat.

Attached a test 3 log, it is a windows text file. If you need a bigger one I will provide it.


Re: Communication only in Monitor mode

PostPosted: Fri Oct 16, 2015 9:14 pm
by hvxl
The signal from the boiler is really not very tidy, but at first glance the gateway should be able to decode it most of the time. You're saying it's not doing that?

Perhaps there's one particular message it has trouble with. A thermostat will usually repeat a message as long as it doesn't get a response. If there's one consistently troublesome message, that would lead to a communication failure in gateway mode.

Could you collect some logs with the regular firmware in both gateway and monitor mode? That way I can see if there's a special message I should focus on.

Re: Communication only in Monitor mode

PostPosted: Sat Oct 17, 2015 1:25 pm
by ilcalmo
In gateway mode the thermostat does not connect to the boiler. The thermostat powers up and says "Connecting" forever and on the boiler display I do not see connection symbol. If I switch to Monitor mode, I have to disconnect the thermostat from the otgw and then connect again to let it work. Then connection starts and I see some values in the logs.

Attached you can find logs in Monitor mode and in Gateway mode.

I also tried to connect the otgw very close to the boiler, 1mt of total wiring, but nothing changed.

Please let me know if you need more logs.

Thanks for your help.

Re: Communication only in Monitor mode

PostPosted: Sun Oct 18, 2015 10:56 am
by hvxl
Very interesting. The first remarkable thing in the logs is that the thermostat sends a message querying smart power support and then immediately switches to medium power mode. Normally I would expect the thermostat to wait for a response from the boiler to confirm that it also supports smart power.

Medium power mode means that the boiler should invert its output. Looking at the incidental Error 02 messages in your logs, it looks like the boiler is doing that regardless, or perhaps based on the Opentherm Member ID in the Master configuration message.

In Gateway mode, the gateway doesn't forward the medium power switch command. However, there are a number of Error 02 responses from the boiler where the gateway decoded the message as 2FFDFEE3. Inverted that reads as D002011C, which is the expected response to a 1002011C request.

Now the question is if the boiler always runs in medium power mode, or if it switches based on the BRAHMA Member ID. To test that, disconnect the gateway from both the boiler and the thermostat. We want the boiler to forget about the Member ID it received earlier. You may even want to power down the boiler to be absolutely sure. Then connect the gateway to the boiler without a thermostat connected. The gateway will start sending Opentherm messages without providing the BRAHMA Member ID. If that works you won't need a firmware change.

If you see responses to the Opentherm messages generated by the gateway, you can send the serial command UI=2 to the gateway. After that command the gateway will not send the Master configuration message to the boiler.

If that doesn't help, the boiler is apparently always in medium power mode. That means that even though it claims to be an Opentherm boiler, it won't work with most Opentherm thermostats. In that case you'll need a small firmware fix.

Re: Communication only in Monitor mode

PostPosted: Fri Oct 23, 2015 12:34 pm
by ilcalmo
back again, I have been out for some days.

I installed 4.2.5 firmware into the gateway and I made the tests as well as you suggested.
I powered off the boiler and then powered on again without no device connected.
Then I connected only the gateway to the boiler, and I could see values. I sent the command UI=2 (in the miscellaneus tab) to the gateway, and then I connected the thermostat. After that, no more values, just error messages, the thermostat says "Connecting..." and after a while there was a gateway reset, and no messages and no data coming anymore.

Any hints?
Attached the log.

Thanks for your help.

Re: Communication only in Monitor mode

PostPosted: Sat Oct 24, 2015 6:25 pm
by hvxl
So it looks like your boiler does indeed react on the Vendor ID of the thermostat. Without the thermostat there are quite a few errors, but many more correct messages.

I was a bit puzzled why my proposed work-around then didn't have the desired effect. The log shows that the gateway still forwards the Master configuration message to the boiler, even though you indicated that the boiler doesn't support it.

Then I checked your log for alternative messages. There aren't any! That means that the list of alternatives must be empty. That will thwart the work-around. So please pick a message that the boiler does support (e.g. 25) and add that as an alternative (AA=25). Then try again.

Re: Communication only in Monitor mode

PostPosted: Mon Nov 09, 2015 1:17 pm
by pak
I'm trying to understand the logic behind the UI, KI, AA and DA commands.

My OTGW is operational for almost a year but keeps generating errors 03 and 04.
I suspected the cabling and have played with resistor values and reference voltage settings (VR) but all to no avail.

When I saw this post, which partly resembles the symptoms I observe, I tried the suggestions to set UI=2 and AA=25. Although it is a bit early to draw conclusions, it looks as if the problems are gone.
I have not seen any errors 03 and 04 anymore, and I don't have to use exotic VR settings anymore.
VR = 1,2 and 3 are running fine. With VR=0 and 7..9 there is no communication at all, and VR=4..6 do work, but with errors now and then. Given the fact that VR=3 is the default setting, this looks ok.

However, I am a bit confused about how the UI, KI, AA and DA command work.
The doc says that the UI command informs the gateway that the boiler doesn't support the specified Data-ID, even if the boiler doesn't indicate that by returning an Unknown-DataId response. Using this command allows the gateway to send an alternative Data-ID to the boiler instead.
I also understand that one has to specify one or more alternative commands with AA, otherwise the UI command is useless.


1. In which cases are commands from the AA table used?
2. The AA table can have contain more than one alternative command. How does the OTGW choose which one to use?
3. Why is is possible to have multiple entries with the same ID in the AA table? Is this by design, or just because it wasn't worth the effort to avoid this?
4. Is there a way to show/list what is in the UI and AA tables?
5. If not, how can I be sure that there are no entries left over from earlier experiments? In other words, is there a way to entirely clear the AA and UI lists?

Thanks for your help,

(Remeha Calenta, iSense rev. 19, OTGW 4.2.5)

Re: Communication only in Monitor mode

PostPosted: Thu Nov 12, 2015 6:27 pm
by hvxl

1. Whenever the thermostat requests a MsgID the gateway has learnt or was told is not supported by the boiler.
2. Every time an alternative MsgID is needed, it picks the next one from the list. When the list is exhausted it restarts from the top.
3. This allows you to increase the frequency of one alternative compared to others.
4. After you have upgraded/reloaded the firmware with the transfer settings box selected, you get an option to show the transferred settings. This includes the UI and AA tables.