about feature value

[Jim]

1. As a slave device, how do I update the content of a feature value when I set a feature value to the property of read?
2. The local setting can set the data of the feature value to be greater than 20 bytes. When the peer device reads a certain feature value of the local device, it reads data greater than 20 bytes at a time.

[Kenneth]

Hi,

Not sure if I understand the question, but you may take a look at the blinky example in the SDK:

\nRF5_SDK_15.2.0_9412b96\examples\ble_peripheral\ble_app_blinky\
(http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.2.0/ble_sdk_app_blinky.html?cp=4_0_0_4_1_2_3)

You can find in ble_lbs_init() that the read propery is set in:

    // Add Button characteristic.
    memset(&add_char_params, 0, sizeof(add_char_params));
    add_char_params.uuid              = LBS_UUID_BUTTON_CHAR;
    add_char_params.uuid_type         = p_lbs->uuid_type;
    add_char_params.init_len          = sizeof(uint8_t);
    add_char_params.max_len           = sizeof(uint8_t);
    add_char_params.char_props.read   = 1;  // Here read property is set.
    add_char_params.char_props.notify = 1;

    add_char_params.read_access       = SEC_OPEN;
    add_char_params.cccd_write_access = SEC_OPEN;

    err_code = characteristic_add(p_lbs->service_handle,
                                  &add_char_params,
                                  &p_lbs->button_char_handles);

The value is updated in ble_lbs_on_button_change() by calling sd_ble_gatts_hvx(), this will update the value and also send a notification if enabled.