IoT Central properties flick between correct data and 'No Value'

Question

I have an Azure IoT Central device that has a number of read-only properties and also some telemetry capabilities defined. In the device views, the properties are displayed correctly most of the time, but periodically (about every ten seconds) the display will switch to showing 'No Value' briefly and then revert to the correct data.

The properties are written to once and telemetry data is sent from the device every minute, so the 'No Value' isn't triggered by an event being received.

Data being displayed correctly:

Briefly showing 'No Value':

Does anybody have any ideas what's happening here?

Answer 1

Hi @Matthew Pass Greetings! I have tested this scenario by creating a test read-property on a custom device template. Posting this as an answer as it might help other community members. I have updated the property only once using SDK code similar to below

private async Task SendDeviceSerialNumberAsync(CancellationToken cancellationToken) {     
    const string propertyName = "serialNumber";     
    TwinCollection reportedProperties = PnpConvention.CreatePropertyPatch(propertyName, SerialNumber);
 	await _deviceClient.UpdateReportedPropertiesAsync(reportedProperties, cancellationToken);
    var oBrace = '{'; 
    var cBrace = '}';   
   _logger.LogDebug($"Property: Update - {oBrace} \"{propertyName}\": \"{SerialNumber}\" {cBrace} is complete."); 
}

The sample is obtained from part of the TempertarureControllerSample.cs The updated property is reflecting the correct view as expected even when the device is disconnected. Please refer the below image for reference.

I appreciate it if you give this approach a try and let me know your observations on this. If you are already using this approach, kindly inspect your source code and verify if there are any part of the application that is modifying the device twin properties.

Please keep us posted on your findings. We would be glad to assist you further on this.

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