Domiot MQTT Client

This project is the P1 smart meter reader implemented in C++. It has to the following requirements.

• The software runs on an ESP8266 device.
• The software shall use MQTT to publish to 'register' and 'sensor' topics.
• It shall support one device with multiple sensors.
• Upon startup it shall connect to wifi using the configured parameters
• Upon startup it shall connect to the configured MQTT broker.
• It shall read a configuration (device.json and general configuration config.json) from Little FileSystem.
• When one or more sensorIds are configured to be 0, a registration process shall start.
  • The registration of the device to the Domiot backend shall be done by publishing the device configuration on the 'register' mqtt topic
  • The device shall wait for a Device configuration including sensorIds by subscribing to the 'config' topic
  • It shall update it's device configuration with information received from the received config message.
  • The registration shall be done once during startup.
• It shall read P1 datagrams from a smart meter on the Rx port.
• It shall publish values for all sensors configured in the device.json.
• It shall support either reading a battery level or a temperature on A0 analog input.
• It shall support reading temperature and humidity from a DHT11 sensor on D7 digital input.
• It shall publish sensor values of all configured sensors at a one second rate.

Future requirements

• Update configuration at runtime
• Publish diagnostics
• CRC validation P1 datagram

Hardware requirements

• The data line (5) of the P1 meter must be attached to the input (1) of a 74HC04 inverter.
• The Rx port of the ESP8266 is attached to the output (2) of the same 74HC04 inverter port.
• The data line needs a pull up resistor of 10k connected to the 5V at the data line (5).
• The data ready line (3) of the P1 meter must be connected to 5V
• The data ground (3) of the P1 meter must be connected to GND of the ESP8266.

Build

Build the firmware image with:

pio run -e nodemcuv2

This produces the firmware image at .pio/build/nodemcuv2/firmware.bin.

OTA Updates

The firmware exposes the ElegantOTA web updater on /update after the device has joined WiFi. The OTA-capable firmware must be flashed over USB once before OTA uploads can work.

OTA authentication is enabled automatically when credentials are available:

• ota.username and ota.password from data/config.json are used when both are set.
• If this pair is not configured, the /update endpoint stays unauthenticated.

Example configuration:

{
	"wifi": {
		"ssid": "MYSSID",
		"password": "thekey",
		"hostname": "domiot-p1-wifi"
	},
	"mqtt": {
		"host": "192.168.1.10",
		"port": 1883,
		"user": "johndoe",
		"password": "secret",
		"client_id": "domiot-p1"
	},
	"ota": {
		"username": "johndoe",
		"password": "secret"
	}
}

Browser Upload

1. Build the firmware.
2. Find the device IP address from the serial log.
3. Open http://<device-ip>/update in a browser.
4. Upload .pio/build/nodemcuv2/firmware.bin.

PlatformIO OTA Upload

The project includes a dedicated OTA environment that uploads to ElegantOTA over HTTP without replacing the normal serial upload flow.

Use:

pio run -e nodemcuv2-ota -t upload --upload-port <device-ip>

Example:

pio run -e nodemcuv2-ota -t upload --upload-port 192.168.1.50 \
  --project-option "custom_username=myuser" \
  --project-option "custom_password=mypass"

The uploader reads credentials from data/config.json using the same fallback order as the device. If you prefer a fixed URL in your local configuration, add this to platformio.ini locally:

[env:nodemcuv2-ota]
custom_upload_url = http://192.168.1.50

If you need to update the filesystem image manually through the web UI, use .pio/build/nodemcuv2/littlefs.bin.