ESP32 code for reading data from Xiaomi MiTemp LYWSDCGQ and LYWSD03MMC sensors. It is supossed to run on ESP32 using arduino-esp32 SDK. It was tested with version 1.0.4 and attached patch to support multiple service data (needed for LYWSDCGQ sensor).
- LYWSDCGQ - round one with LCD display powered by one AAA battery
- LYWSD03MMC - small square one with LCD display with great price / performance ratio
Code consists of base BleAdvListener class that handle all needed for listening and extracting service data from BLE devices. On the top of that are classes for each sensor. Data from LYWSDCGQ sensor are extracted directly from ADV packets. Data from LYWSD03MMC sensor can be received by doing BLE connection and requesting notification from sensor (tested only on regular firmware) or passivly by extracting data from ADV packets (like for LYWSDCGQ). For that to work you need to know your encryption key, because data in ADV packets are encrypted or use custom firmware (see bellow). All is prepared for very simple usage. Example code that reads data from both types of sensors at the same time and exporting it using simple HTTP api is located in mitemp_ble_gw_esp32.cpp file. After changing file extension it should be possible to compile it also in Arduino Studio (original code was developed in Sloeber IDE).
How to get encryption key is described in Home assistant component readme
There's a great project ATC_MiThermometer where you can find custom firmware for LYWSD03MMC sensor. Installing this firmware will give you great features, like unencrypted data in ADV packets (you don't need to pair device anymore after batery replacement), display of battery status right on display, custom name with mac address in it (great if you have many sensors) and so on. Installing firmware is really simple, so I definitely recommend it. The original project was also forked HERE by pvvx. It contains many modifications and introduced also another custom format of ADV packets. Data format for all these firmwares is supported.
This version doesn't support multiple service data in included BLE library. You need to patch it using included multiple_services.patch file.