HabPanel: USB C resistors?

I’m replacing a thermometer with a wall mounted Fire HD running HabPanel connected to a Nano that controls the HVAC relays. I’ve written an MQTT <-> Serial background service for the Fire. The difficulty is the USB C on the Fire. I have tried various cables and DIY solder USB C connectors and can either power the devices or have serial comms working, never both. I think I need a particular combination of resistors on the CC1 and CC2 lines but every guide seems oriented to either charging or serial comms. Anyone know the right combination of, I think, 56K and 4.7K resistors on those lines?

Have you considered using a bluetooth to serial adapter instead of trying to use the cable? I have used ones similar to these when interfacing serial devices and android. Granted I use them mostly for Ham radio, but same concept.


That is definitely the fall back option. I could also have the thermometer be completely separate using WiFi, RF directly back to the OpenHAB RPI but the stubborn engineer in me would like to find what must be a path here. I already have to have a cable in the Fire for power and the serial lines are just sitting there for a nice robust connection…if only I could decipher the pesky USB C standard.

Does the specific Fire device support both concurrently? that may have been a design decision for them to not support both.

I may well be running into that…not sure where I’d look that up but definitely a possibility. I do know there is a combination of CC line resistors I haven’t tested, because I’m not sure what to test! Anyway, probably time to start on Plan B.