Terma Blue Line (bluetooth radiators and heating elements)

Hardware
21

Yes, you have to pair it.

try bluetoothctl (interactive mode, put the heating unit in pairing mode) and then type:

default-agent
scan on
pair AA:BB:CC:DD:EE:FF
char-read-hnd 19
char-read-hnd 17
disconnect
exit

Where AA:BB:CC:DD:EE:FF is the MAC address of the unit.

char-read-hnd 19 will get you the current mode (08 in my case when it’s on schedule, heating element temp)

char-read-hnd 17 will get you something like AABBCCDD where AABB is current temp and CCDD is target temp; call temperatureTermaToCelsius('AA', 'BB') or temperatureTermaToCelsius('CC','DD') to convert to celsius.

To change the mode:
char-write-req 19 00 will put in mode “0” which means off.

1 Like
22

I can’t for the life of me get it to pair.
Hold down the icon until it flashes blue/green

Then when I pair I get:

[bluetooth]# pair AA:BB:CC:DD:EE:FF
Attempting to pair with AA:BB:CC:DD:EE:FF
[CHG] Device AA:BB:CC:DD:EE:FF Connected: yes
Failed to pair: org.bluez.Error.ConnectionAttemptFailed
[CHG] Device AA:BB:CC:DD:EE:FF Connected: no

(obviously with my MAC not AA:BB:CC:DD:EE:FF)
Maybe there’s something up with the bluetooth on my RPi :man_shrugging:

23

I’ve managed to get it to work on an old Buster as well as on the latest Bullseye with the standard RPI bluetooth.

Make sure you do scan on first. Check the list, does it sees you heating unit? It might be a matter of being too far / signal not being great.

24

Yeah, it usually sees it straight away on the scan, and then the pairing connect/fail happens really fast :man_shrugging:
Will have a play around with it when I get more time.
Cheers :+1:

25

It can be tricky at time to pair. Try turning the unit off (by unplugging it / turning the mains switch off) and on again. Do scan first, check the unit is shown, then put it in pairing mode and pair it on RPI (it will ask you for the pin code which is 123456). Once that’s done, the rest is easy :blush:

26

I just cannot get it to pair :sob:
Tried so many times, but it fails every time.
Think I’m going to give up for now, but I may come back to it in a few months when I’ve dredged up the enthusiasm to try again :rofl:

27

Have anyone managed to create an Esphome project / component for this?

28

I have started, but paused attempts to connect from an ESPHome board. It was initially successful: I could pair and retrieve data as the first step, with the intention of adding control later.

However, the problem I encountered was that the connection/pairing (? not sure which) would come undone after a day or two. As far as I could tell at the time the only way to get it to reconnect was to put the radiator back into pairing mode.

I’ve not had time to dig deeper but it seemed as though the problem was possibly on the ESPHome+Bluetooth stack side, forgetting something about the pairing. A paired iPhone+Terma app, by contrast, has no trouble re-establishing a connection to the radiator after any amount of time.

As a general note for anyone trying to reverse engineer the protocol: the Android Terma BlueLine Next app APK is a Phonegap/Cordova-based app, so contains a wealth of interesting and quite readable JS code :wink:

29

I’m connecting to the Terma unit by having NodeJS running gatttools in interactive mode, so I can poll from time to time.

I initially had it opening a connection, poll, close a connection but that proved to be problematic since it uses a lot more Bluetooth traffic and it is more likely to fail in busy radio environments. I’ve switched to persistent Bluetooth connection with reconnect logic in case of failure.

It works well. So I guess you have an issue with the hardware. Either on esp or terma side.

Re: the app, I didn’t noticed it is Cordova. But android apps can be decompiled anyhow…