https://hackaday.com/2020/12/08/exploring-custom-firmware-on-xiaomi-thermometers/
https://github.com/atc1441/ATC_MiThermometer
https://github.com/pvvx/ATC_MiThermometer
Xiaomi Smart LCD Screen Digital Thermometer 2 Mijia Bluetooth Temperature Humidity Sensor Moisture Meter Mijia App
https://www.aliexpress.com/item/1005002401046796.html
LYWSD03MMC
root@rpi2:/home/pi# sudo hcitool lescan LE Scan ... A4:C1:38:D8:3F:9C ATC_D83F9C
https://github.com/bentolor/xiaomi-mijia-bluetooth-firmware
https://github.com/dpavlin/air-quality/blob/master/ble-mijia.sh
https://github.com/dpavlin/air-quality/blob/master/system/ble-mijia%40.service
https://www.youtube.com/watch?v=NXKzFG61lNs
connected to home assistant using https://esphome.github.io/bluetooth-proxies/
get bindkey using https://atc1441.github.io/TelinkFlasher.html
https://esphome.io/components/sensor/xiaomi_ble.html?highlight=xiaomi_ble#obtaining-the-bindkey
[core-ssh ~]$ tail -18 config/.storage/core.config_entries { "entry_id": "574243c45c4485523ec174e18cfcf1ad", "version": 1, "domain": "xiaomi_ble", "title": "Temperature/Humidity Sensor DC63 (LYWSD03MMC)", "data": { "bindkey": "a6da0c1d99200efe9c9afb8fd9a534ef" }, "options": {}, "pref_disable_new_entities": false, "pref_disable_polling": false, "source": "bluetooth", "unique_id": "A4:C1:38:90:DC:63", "disabled_by": null } ] }
flash new firmware to sensor https://github.com/pvvx/ATC_MiThermometer
open in chrome on android to flash firmware,
change announcement to BTHome,
set time,
disconnect to start sending data to home assistant
pinout
DTR - 3V3 (so that reset works)
GND - GND
TX - P14 - SWS
https://pvvx.github.io/ATC_MiThermometer/USBCOMFlashTx.html
https://github.com/pvvx/TlsrComSwireWriter
https://github.com/pvvx/ATC_MiThermometer?tab=readme-ov-file#reed-switch-or-button-functions
It is possible to solder a reed switch on the LYWSD03MMC board to the pins marked "P8" (GPIO PA6) and GND.