Attribute#

Attributes represent the current state of a device. For instance if the device is on or off, the current temperature, or the current level of a dimmer. Attributes are defined in the cluster specification.

Attribute Changes#

When a ZCL attribute is updated in the data model, the framework will call the postAttributeChangeCallback. If this callback is implemented by the device it will be informed of the attribute change. The device may react to the attribute change. For example, in the MatterPostAttributeChangeCallback, say we want to add some custom handler code to control an RGB LED when on/off attribute in the On-Off Cluster changes:

void MatterPostAttributeChangeCallback(const chip::app::ConcreteAttributePath & attributePath, 
                                        uint8_t type, 
                                        uint16_t size,
                                        uint8_t * value)
{
    ClusterId clusterId     = attributePath.mClusterId;
    AttributeId attributeId = attributePath.mAttributeId;
    ChipLogProgress(Zcl, "Cluster callback: " ChipLogFormatMEI, ChipLogValueMEI(clusterId));

    if (clusterId == OnOff::Id && attributeId == OnOff::Attributes::OnOff::Id)
    {
        /* Custom code */
        if (*value) 
        { // turn on LED
            sl_led_turn_on((sl_led_t *)&sl_simple_rgb_pwm_led_rgb_led0);
        } 
        else 
        {// turn off LED
            sl_led_turn_off((sl_led_t *)&sl_simple_rgb_pwm_led_rgb_led0);
        }
        /* ----------- */
    }

    //...
}

Header File#

This file contains the high level namespaces and constant definitions for Attributes. In Simplicity Studio, this will be generated in the autogen/zap-generated/ folder of the matter project.

• Attribute