Approaches for Effcient Payload Encoding

Application Development
3

Yes - I have found nanopb to be an incredibly convenient option for my app, where there are a highly-variable combination of “required” and “optional” fields. The encoding is really efficient and it is trivial to program.

Some people find it easier to understand if they see an example, so here’s a snippet from one of my projects:

{
    // Allocate space on the stack to store the message data
    teletype_Telecast message = teletype_Telecast_init_zero;

    // Create a pb stream within that buffer
    pb_ostream_t stream = pb_ostream_from_buffer(buffer, sizeof(buffer));

    // Set fields marked as required in .proto
    message.DeviceType = teletype_Telecast_deviceType_BGEIGIE_NANO;
    strncpy(message.DeviceID, DeviceID, sizeof(message.DeviceID));
    strncpy(message.CapturedAt, DateTimeISO, sizeof(message.CapturedAt));
    message.Unit = teletype_Telecast_unit_CPM;
    message.Value = RadiationCPM;

    // Set fields marked as optional in .proto
    if (GPSValid) {
        message.Latitude = GPSLatitude;
        message.Longitude = GPSLongitude;
        message.Altitude = GPSAltitude;
        message.has_Latitude = 
            message.has_Longitude = 
            message.has_Altitude = true;
    }

    // Encode and transmit the message
    status = pb_encode(&stream, teletype_Telecast_fields, &message);
    if (!status)
        DEBUG_PRINTF("pb_encode: %s\n", PB_GET_ERROR(&stream));
    else
        send_to_ttn(buffer, stream.bytes_written);

}
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