Fun using NCEU 2018 Badge (Pixl.js variant) with BTHome and Home Assistant

[conoro]

Long time no talk on the Espruino forums.

I went down a rabbit hole yesterday wondering if I could get ESPHOME running on the NodeConfEU 2018 badge as I saw it now supports NRF52.

Whilst it could work, the lack of SPI support etc made it a waste of time.

Then I discovered that Gordon had already implemented the BTHome protocol on Espruino, making it out-of-the-box compatible with Home Assistant!

More people should know about this as it just works and you get the full capabilities of Espruino on NRF52832, not just the heavily limited ESPHOME implementation.

I got Claude Code + Opus 4.6 to write the code in 5 minutes for a Temperature sensor. Adding a clock with regular sync took longer as I ended up with an ESP32 as a HA relay/time-beacon. I'm sure there's an easier way.

Code: https://gist.github.com/conoro/72f83955f74b47ad87ceecc8344e63d7

The only minor downside is that the temperature is wildly wrong 😆

[gfwilliams]

Good to hear from you again - this is great! The temp sensor actually isn't that bad, but you just have to calibrate the offset on it :)

ESP32 as a HA relay/time-beacon

Ohh. Do you have more info on how you did this? Is it possible with ESPHome + Home Assistant? What we're really missing is the ability to easily get data from Home Assistant to bluetooth devices.

The closest I got was https://www.espruino.com/ble_led (faking a BLE device that HA supports) but it's far from ideal.

... I really wanted to make an Espruino integration for Home Assistant that let you push data over the Nordic UART, but the learning curve has been a bit too steep for me to get anything useful in a few hours.

[conoro]

I'll give that calibration a go. Currently 3C or so too high.

I (Claude) had a few goes at the relay. Initially it was trying to push into the UART but I didn't have much success. Eventually I nudged it to just use a broadcast of the time.

The main challenge, as I'm sure you know, is that HA doesn't transmit over BLE, it only receives. So the relay is just an ESPHOME WiFi+BLE device that reads HA time over WiFi and then broadcasts it over BLE. A bit crude as it doesn't update continuously.

I used a random classic ESP32 device I had lying around but I've been been doing a lot more with the ESP32-C6 and ESP32-H2 recently. The C6 has BLE, WiFi, Zigbee and Thread. The H2 is the same but no WiFi and slower. Both are RISC-V and both mostly supported by ESPHOME (not Zigbee tho, that needs ESP-IDF).

The Espruino code and the ESPHOME config are here: https://gist.github.com/conoro/72f83955f74b47ad87ceecc8344e63d7

[gfwilliams]

That's great, thanks! I didn't spot the ESPHome config before - that's a really nifty addition. For Nodeconf we rotated the advertising messages every so often to transmit more data, and it feels like that could definitely happen here if needed.

HA doesn't transmit over BLE, it only receives

Well, for advertising... ESPHome itself can connect and change characteristics, as integrations like LED BLE manage it using the bleak API that's exposed (I've used that and also another one that writes to smart thermostats).

There's an integration which supposedly allows you to write to arbitrary bluetooth characteristics (which could include Nordic UART) at https://community.home-assistant.io/t/generic-bluetooth-integration/648952 but as far as I can tell it doesn't automatically disconnect from the given device, which isn't great. It feels really close to being usable though