nrf9160: Publish a custom topic to Azure IoT Hub using Nordic Azure IoT Library

Question

Hi everyone,

from our nRF9160 device I need to send data to our customers Azure IoT Hub instance, but I have no luck to receive anything on the cloud side so far. The data is a protobuf message which should be included within the MQTT message. This message should sent (published) to a certain topic specified by the custome like this:

devices/<device-id>/messages/events/device_id=<device-id>

For e.g. the topic would look like this:

devices/350914768187078/messages/events/device_id=350914768187078

Now I have spent days to find out, how I can alter the MQTT topic to my needs when using Nordics Azure IoT Library. I use a "azure_iot_hub_message" structure (from Nordics Azure IoT Hub Library), in which I have changed the topic name to

devices/350914768187078/messages/events/

and added a property (key/value pair) with

key = "device_id"

value="350914768187078"

Is this the correct approche to change the topic to our needs? Here the code snippet to show how I have done it in code:

    static uint32_t msg_id = 0;
    int err;
    uint8_t* payload = NULL;
    ssize_t len;

    len = protobuf_EncodeUsageUpdateObject(&payload); // payload holds the packed protobuf message (UsageUpdate object)

    char topic[] = "devices/350914768187078/messages/events/";

    char key1_string[] = "device_id";
    char value1_string[] = "350914768187078";

    struct azure_iot_hub_buf key1 = {
        .ptr = key1_string,
        .size = sizeof(key1_string),
    };

    struct azure_iot_hub_buf value1 = {
        .ptr = value1_string,
        .size = sizeof(value1_string),
    };

    struct azure_iot_hub_property prop = {
        .key = key1,
        .value = value1,
    };

    struct azure_iot_hub_msg msg = {
        .topic.type = AZURE_IOT_HUB_TOPIC_EVENT,
        .topic.name = topic,
        .topic.name.size = sizeof(topic),
        .topic.properties = &prop,
        .topic.property_count = 1,
        .payload.ptr = payload,
        .payload.size = len,
        .message_id = ++msg_id,
        .qos = MQTT_QOS_1_AT_LEAST_ONCE,
    };

Thanks in advance.

BR

Thomas

tkeilbach · Accepted Answer

Hi Dejan, 
 yes, my application is based on the Azure IoT Hub sample. 
 In the meantime the customer cloud guys came back with the info that the receive the data. So for everyone with a similar problem, the code above works fine if you want to change the topic and append a property bag. 
 Thanks for all! 
 BR 
 Thomas

nrf9160: Publish a custom topic to Azure IoT Hub using Nordic Azure IoT Library

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