refer to <a href="https://developer.mbed.org/forum/team-63-Bluetooth-Low-Energy-commun

Update, this is what I'm currently using: <div class="highlight highlight-source-c

add API to enable notifications about ble HOT 4 OPEN

armmbed commented on July 17, 2024

add API to enable notifications

from ble.

Comments (4)

remay commented on July 17, 2024

Just for the record I have been using this extension to DiscoveredCharacteristics, which is very similar to your proposed DiscoveredCharacteristic::enableNotification():

ble_error_t
DiscoveredCharacteristic::requestHVX(HVXType_t type) const
{
    if (!props.write()) {
        return BLE_ERROR_OPERATION_NOT_PERMITTED;
    }

    if (!props.notify()) {
        return BLE_ERROR_OPERATION_NOT_PERMITTED;
    }

    if (!gattc) {
        return BLE_ERROR_INVALID_STATE;
    }

    /* Cargo Culted from: https://developer.mbed.org/teams/Bluetooth-Low-Energy/code/BLE_ButtonSense/file/2dec89c76f68/main.cpp */
    /* HACK. We're assuming that CCCD descriptor immediately follows the value attribute. */
    /* TODO actually discover the handle for the CCCD descriptor */
    uint16_t value = (uint16_t)type;
    return gattc->write(GattClient::GATT_OP_WRITE_REQ, connHandle, valueHandle + 1, sizeof(value), (const uint8_t*)(&value));
}

I know it doesn't solve the real problem of descriptor discovery, but it does hide away the hack to somewhere that they can be worked on without effecting user code.

from ble.

remay commented on July 17, 2024

And, of course, having posted that I see that the second test in not correct for indications, that have their own property. But you get the idea.

from ble.

remay commented on July 17, 2024

Update, this is what I'm currently using:

DiscoveredCharacteristic::requestHVX(HVXType_t type) const
{
    if (type == BLE_HVX_NOTIFICATION && !props.notify()) {
        return BLE_ERROR_OPERATION_NOT_PERMITTED;
    }

    if (type == BLE_HVX_INDICATION && !props.indicate()) {
        return BLE_ERROR_OPERATION_NOT_PERMITTED;
    }

    if (!gattc) {
        return BLE_ERROR_INVALID_STATE;
    }

    /* Cargo Culted from: https://developer.mbed.org/teams/Bluetooth-Low-Energy/code/BLE_ButtonSense/file/2dec89c76f68/main.cpp */
    /* HACK. We're assuming that CCCD descriptor immediately follows the value attribute. */
    /* TODO actually discover the handle for the CCCD descriptor */
    uint16_t value = (uint16_t)type;
    return gattc->write(GattClient::GATT_OP_WRITE_REQ, connHandle, valueHandle + 1, sizeof(value), (const uint8_t*)(&value));
}