Lowest power while keeping app timers running

RE: Lowest power while keeping app timers running

Vidar Berg — Thu, 15 May 2025 07:02:13 GMT

The app timer runs independently of the softdevice and they do not share the same IRQ. However, it will stop running if the LFCLK is released when disabling the softdevice (which can happen if you use nrf_sdh_disable_request()).

You can try using the function below to stop BLE activity before entering the low power mode.

static void ble_stop(void)
{
    /* 
     * The default behavior when using the Advertising module is that the
     * advertiser will automatically restart on disconnect, but here
     * we need the advertiser to remain disabled. To acheive this we can set the
     * ble_adv_on_disconnect_disabled flag to 'true' in the advertiser configuration.
     * 
     * Important: Remember to reset this flag when exiting low power mode to restore
     *            default behaviour.
     *
     * https://docs.nordicsemi.com/bundle/sdk_nrf5_v17.1.0/page/lib_ble_advertising.html 
     */
    m_advertising.adv_modes_config.ble_adv_on_disconnect_disabled = true;

    (void)sd_ble_gap_adv_stop(0);
    (void)sd_ble_gap_disconnect(0, BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
}

RE: Lowest power while keeping app timers running

SteveHx — Wed, 14 May 2025 14:56:21 GMT

If I understand correctly, disabling the IRQ will also disable my app timer, which needs to keep running to determine when to wake everything back up. It is possible a connection will be active, so what function is the correct one to call to shut down the connection, and what function to stop advertising?

RE: Lowest power while keeping app timers running

Vidar Berg — Wed, 14 May 2025 14:51:09 GMT

There isn't a single function to stop all BLE activities. Is the device always advertising before entering this low power mode, or could it also be in a connection? nrf_sdh_suspend() disables the SoftDevice IRQ which is not what you want in this case.

RE: Lowest power while keeping app timers running

SteveHx — Wed, 14 May 2025 14:13:36 GMT

Is nrf_sdh_suspend () the correct function to use here, to stop all BLE activities?

RE: Lowest power while keeping app timers running

Vidar Berg — Wed, 14 May 2025 14:08:04 GMT

Hello,

It is sufficient to stop any ongoing bluetooth activities (such as stopping the advertiser or terminating an active connection). It's not necessary to disable the softdevice as it won't affect the idle current.

Best regards,

Vidar