Sensor network thingie

Home gateway for communicating with nRF24L01+ sensors spread around my house.

Communicates with /dev/ttyUSB0. Probably requires sudo.

Forwards data to mqtt server.

Config

Create .env with

ENV VAR	Default	Description
MQTT_HOST	-	mqtt hostname (e.g. mqtt://localhost)
MQTT_USERNAME	-	mqtt username
MQTT_PASSWORD	-	mqtt password
DEVICE	/dev/ttyUSB0	Device as found on host

Sensors

Sensors are identified by id and type. The type IDs are:

Type ID	Type	Description
1	Temperature	Temperature sensor
2	Door sensor	Door sensor

All emit a message on mqtt in topic home/nrf24l01/{id} where {id} is the id of the sensor.

Temperature

A sensor broadcasting the temperature in Celcius.

byte	desc
0	sensor id
1	type id
2	battery (0 - 254 as percentage and 255 for no battery)
3-4	MSB value of temp * 100. (temp = (data[3]*256 + data[4]) / 100)

Message looks like

{
  sensorId: ID of the sensor
  voltage: value between 0-254 indicating % of charge, or 255 indicating no battery or voltage unknown.
  type: 'temp'
  timestamp: epoch in milliseconds
  temp: the temperature reading in degrees celcius
}

Door

byte	desc
0	sensor id
1	type id
2	battery (0 - 254 as percentage and 255 for no battery)
3	1 if open and 0 if closed

Message looks like

{
  sensorId: ID of the sensor
  voltage: value between 0-254 indicating % of charge, or 255 indicating no battery or voltage unknown.
  type: 'door'
  timestamp: epoch in milliseconds
  open: true of the door is open and false if it is closed
}