How to add extra Informations to sensors and send them to Node Red?

scoe · April 15, 2024, 3:20pm

Hey folks,

some time ago we added some sensor for monitoring airquality. In Node Red we then prepare the received data (co2, temperature and humidity) to be conform with our data model.
Is there a way to add something like room or building for every sensor and send these data to Node Red as well?
Is this possible with self added attributes?

Best regards

bertrik · April 15, 2024, 3:57pm

Yes, you can add a device-specific attribute in the console.

However the device-attribute data is not sent with each MQTT uplink message. You need to fetch the attributes in a separate process.

See for example:

scoe · April 15, 2024, 4:43pm

However the device-attribute data is not sent with each MQTT uplink message

Is there some logic behind this? Or what should I expect here?

Thanks your your help so far

kersing · April 15, 2024, 5:40pm

Yes, looking up the data is expensive for an environment handling millions of messages. So it’s delegated to a place with less load (your servers).

So get the data periodically and cache it, don’t issue a lookup on every message…

Johan_Scheepers · April 15, 2024, 7:42pm

Why do you not just have a lookup table, a MySQL table (for example). Using the eui as a key?

No extra load on the TTN server, and minimal load on yours.

bertrik · April 16, 2024, 7:00am

To fetch the device attributes, you can use the end device API, as described here: End Device APIs | The Things Stack for LoRaWAN

My application uses the EndDeviceRegistry.List call:

github.com

bertrik/sensor-data-bridge/blob/master/sensor-data-bridge/src/main/java/nl/bertriksikken/ttnv3/enddevice/IEndDeviceRegistryRestApi.java#L23


      
          */
          public interface IEndDeviceRegistryRestApi {
             
             // values to be passed to the fieldMask parameter
             public static final String FIELD_IDS = "ids";
             public static final String FIELD_NAME = "name";
             public static final String FIELD_DESCRIPTION = "description";
             public static final String FIELD_ATTRIBUTES = "attributes";
             public static final String FIELD_VERSION_IDS = "version_ids";
          
             // end device registry
             @GET("/api/v3/applications/{application_id}/devices")
             Call<EndDevices> listEndDevices(@Header("Authorization") String authToken,
                     @Path("application_id") String applicationId, @Query("field_mask") String fieldMask);
          
             @GET("/api/v3/applications/{application_id}/devices/{device_id}")
             Call<EndDevice> getEndDevice(@Header("Authorization") String authToken,
                     @Path("application_id") String applicationId, @Path("device_id") String deviceId,
                     @Query("field_mask") String fieldMask);
          
             @PUT("/api/v3/applications/{application_id}/devices/{device_id}")

application_id = the id of the TTN application
Authorization header with an API key that allows permission to view the device properties (‘view devices in application’, perhaps also ‘view application information’)
field mask set to “ids,attributes”

scoe · April 18, 2024, 10:09am

Sounds reasonable and should be enough for my purpose.