Python API - downlink_callback

[arjanvanb (Arjan)]

@goodrun

mqttc.subscribe('+/devices/+/down')

You’ll need +/devices/+/events/down/sent (or a broader wildcard, such as #).

@goodrun

want to store uplink and downlink data to a csv

Do yourself a favor for future debugging and store all events you can get through MQTT. Also, store the time, and the topic you’re getting it on:

@arjanvanb

For logging, one may want to ensure the topic and time are always included:

// A file node only saves msg.payload, but +/+/+/events/down/scheduled
// holds no details about application, device nor timestamp in the
// MQTT payload, but only: 
//   {"message": {"port": 1, "payload_raw": "BA=="}}
// Same goes for TTN-published errors:
//   {"error": "Unable to decode payload fields: Internal error: ..."}}
// So, ensure the topic and time are also saved into the log file:
msg.payload = {
  topic: msg.topic,
  timestamp: new Date().toISOString(),
  payload: msg.payload,
  error: msg.error
}

return msg;