Get the last value for a sensor

rejas

This is a question we got to our support. Since other might be wondering I answer it here as well.

The question was how do I get the latest value from a sensor (=device) using the API?

There are two options for this. Either the log endpoint with limit=1 or, probably better, the status endpoint.

Let's go with the status endpoint. The status API is used for instance if you want the current state of a whole installation. For example to present in a GUI. So without other arguments but the installation ID you get the whole installation.

curl -s -X GET -H "X-API-Key:$TOKEN" https://lynx.iotopen.se/api/v2/status/16

Please note that for large installations this might take a while, but since you get a lot of data it might be worth it.

The key to data is the topic. We can limit what we get by adding topics to the url. Like this:

curl -s -X GET -H "X-API-Key:$TOKEN" https://lynx.iotopen.se/api/v2/status/16?tokens=obj/zwave/usb0/node/9/air_temperature

Example answer:

$ curl -s -X GET -H "X-API-Key:$TOKEN" https://lynx.iotopen.se/api/v2/status/16?topics=obj/zwave/usb0/node/9/air_temperature | jq
[
  {
    "client_id": 16,
    "installation_id": 16,
    "timestamp": 1737011284.733,
    "value": 21.3,
    "topic": "obj/zwave/usb0/node/9/air_temperature",
    "msg": ""
  }
]

I hope this helps!

rejas

If I just want the numeric value for use in a script I can use:

$ curl -s -X GET -H "X-API-Key:$TOKEN" https://lynx.iotopen.se/api/v2/status/16?topics=obj/zwave/usb0/node/9/air_temperature | jq .[].value
21.3

rejas

Topics might be comma separated list of topics, for instance collected by functionx endpoint searching for a specific meta-data. If the list get very long the request might be too large. Then there is also a POST variant of the endpoint.