LYWSD03MMC to MQTT Gateway

Gateway to convert between LYWSD03MMC (Xiaomi Mi Temperature and Humidity Monitor 2) running custom atc1441 or pvvx software Bluetooth Low Energy measurements announcements to the MQTT messages in JSON.

The software has been written for the M5Stack Atom S3 Lite board, but should work on other similar boards with little or no adaptation needed.

Supports messages in the atc1441 and pvvx formats, both non-encrypted and encrypted (feature not available in ESPHome's xiaomi_ble sensor platform).

Configuration

Create settings-private.hpp file that defines:

• WIFI_SSID and WIFI_PASSWORD
• MQTT_SERVER plus optionally any of: MQTT_PORT (default: 1883), MQTT_USER and MQTT_PASSWORD (both default to null), MQTT_CLIENT_NAME_PREFIX (default: M5Stack AtomS3 Lite), MQTT_TOPIC_PREFIX (default: m5stack_atoms3lite_mitemperature)
• DEVICES in the format explained below

Example settings-private.hpp configuration file:

#pragma once

#define WIFI_SSID "YourWiFiSSID"
#define WIFI_PASSWORD "YourWiFiPassword"

#define MQTT_SERVER "192.168.0.1"
#define MQTT_TOPIC_PREFIX "m5stack_atoms3lite_mitemperature"

#define DEVICES { \
            {"A4:C1:38:97:8C:7B"}, \
            {"A4:C1:38:FF:C1:3F", "d553e7cea293deca503a2e036b630503"}, \
            {"A4:C1:38:7A:C0:DB", "68c3b1a07e224df1aa1ddd5e5421ac96", "bathroom"}}

Device configuration

Devices are configured as vector of tuples with one, two, or three elements.

• The first (and mandatory) field is the MAC address of the device.
• The second field is the encryption key in hex. It is used to decode encrypted messages. Ignored for non-encrypted announcements. Can be nullptr if not needed but the third field is used.
• The third field is the custom name to be used in MQTT topic and in the sensor field. If not set, it is the last three octets of the MAC address without colons, i.e., 978C7B and FFC13F in the above example.

MQTT messages

MQTT messages are sent to the per-sensor topics and include all decoded fields (vary by the format). Additionally, the gateway reports its uptime and heap stats to the status topic:

m5stack_atoms3lite_mitemperature/978C7B {"temperature":27.12,"humidity":43.83,"voltage":2976,"battery":100,"sensor":"978C7B","timestamp":1708205031,"rssi":-38}
m5stack_atoms3lite_mitemperature/FFC13F {"temperature":22.94,"humidity":66.74,"battery":64,"sensor":"FFC13F","timestamp":1708205032,"rssi":-71}
m5stack_atoms3lite_mitemperature/bathroom {"temperature":21.48,"humidity":71.16,"battery":65,"sensor":"bathroom","timestamp":1708205041,"rssi":-56}
m5stack_atoms3lite_mitemperature/status {"uptime":180,"heap_8bit_total_free_bytes":202756,"heap_8bit_total_allocated_bytes":128368,"heap_8bit_largest_free_block":192500,"heap_8bit_minimum_free_bytes":196340,"heap_8bit_allocated_blocks":366,"heap_8bit_free_blocks":5,"heap_8bit_total_blocks":371}