MQTT Protocol Documentation¶

Overview¶

IsoPrüfi uses MQTT for sensor data communication between Arduino devices and the backend system. The protocol handles real-time data transmission with recovery capabilities for offline scenarios.

Topic Structure¶

Standard Topic Format¶

{topicPrefix}/{sensorType}/{sensorId}

Example: dhbw/ai/si2023/temp/Sensor_One

Topic Components¶

topicPrefix: Configurable prefix (default: dhbw/ai/si2023/)
sensorType: Type of sensor (temp, hum, co2, spl, mic, ikea)
sensorId: Unique sensor identifier

Message Formats¶

Standard Sensor Reading¶

{
  "timestamp": 1672531200,
  "value": [23.5],
  "sequence": 1234
}

Recovery Data (Bulk Upload)¶

{
  "timestamp": 1672531200,
  "value": [23.5],
  "sequence": 1234,
  "meta": {
    "t": [1672531100, 1672531160, 1672531220],
    "v": [23.1, 23.3, 23.4],
    "s": [1231, 1232, 1233]
  }
}

Data Fields¶

Field	Type	Description
timestamp	DateTime	Unix timestamp (seconds since epoch)
value	float[]	Sensor readings (array for multi-point sensors)
sequence	int	Sequential counter for message ordering
meta.t	DateTime[]	Recovery timestamps
meta.v	float[]	Recovery values
meta.s	int[]	Recovery sequence numbers

Error Handling¶

Failed publishes trigger local storage
Recovery data sent in batches (max 3 files per loop)
60-second timeout for recovery operations
Automatic reconnection on connection loss