Issues related to Matter over Thread product interfaces for reporting brightness changes to the APP

[paper555]

We are developing a light product that features a built-in button. A single click of this button toggles the light on/off, while a long press adjusts the brightness level.

If we manually adjust the brightness and then report the new brightness level via the Clusters::LevelControl::Attributes::CurrentLevel::Set() interface, this action triggers the MatterPostAttributeChangeCallback() command to set the brightness (which involves receiving commands for the transition from the current value to the target value).

Since our intent is solely to report the new brightness to the app without triggering a control command, this creates a conflict.

Is there an interface that allows us to only report the brightness state without subsequently receiving a dimming/setting command?

[Marte Myrvold]

Hi,

The MatterPostAttributeChangeCallback() function is always called when an attribute value is changed, and since the Set() function changes the CurrentLevel attribute, MatterPostAttributeChangeCallback() will be called.

Can you clarify what you mean by MatterPostAttributeChangeCallback() triggering a control command? How have you implemented this function?

Best regards,
Marte

[paper555]

After the device-side button triggers a brightness change, I need to notify the mobile app of the updated brightness state. Which API should I use?

If I use the set() function to report the brightness state, I receive an unwanted brightness change callback (MatterPostAttributeChangeCallback()) during the reporting process.

Is there an API that can directly report brightness without triggering this callback?

[Marte Myrvold]

Hi,

You need to update the attribute value locally on the device, and Set() is the correct way to do this. Can you explain why MatterPostAttributeChangeCallback() being called is causing a problem in your application? 

Best regards,
Marte

[paper555]

When the internal dimming ramp time is set to 10 seconds, I need to notify the mobile app that the target brightness has reached 254. However, after the device reports this brightness update, it receives a series of brightness callbacks (transitioning from 0 to 254) during the fade process. These intermediate values then unexpectedly modify the device's target brightness again, creating an undesirable control loop.

[Marte Myrvold]

Hi,

If you need to update the mobile app only when the brightness has reached 254 and not any values during the transition, the best option is to call Set() only once to update the attribute value once the transition is complete. 

MatterPostAttributeChangeCallback() is automatically called by the Matter Data Model engine directly after an attribute value is changed, regardless of whether the change occurred due to a local action or as a result of receiving a command from a remote device. This is the intended behavior of the callback, and it is meant to synchronize the attribute value between the Data Model and the application state.

You can read more about this in Matter APIs.

Best regards,
Marte