Sleep Immediately after Beacon Advertisement

[Kenny]

I'm using the following code to make the beacon sleep:

static void on_ble_evt(ble_evt_t * p_ble_evt)
{
    uint32_t        err_code;
    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GAP_EVT_CONNECTED:
        {
            break;
        }
        case BLE_GAP_EVT_TIMEOUT:
        {
            if (p_ble_evt->evt.gap_evt.params.timeout.src == BLE_GAP_TIMEOUT_SRC_ADVERTISING)
            {
                sd_ble_gap_adv_stop();
                ble_fsm_set_state(Ble_Fsm_State_Idle);
            }
            break;
        }
        default:
        {
            break;
        }
    }
}

Once the state is set to idle, the nrf51 chip goes to sleep and the current draw drops to the order of uA. My only problem here is that the minimum timeout value is 1s and this means that the chip is burning power for 1s. Ideally, I would like the beacon to just advertise once and then go to sleep immediately. What is the best way to do this? Adding a synchronous delay of 5 ms? Any callback that I can use instead?

[endnode]

What do you mean by "sleep"? I assume that nRF5x chip is going to POWER ON SLEEP (wait for event/interrupt) always when nothing is running on MCU so even between adv. events. If you mean POWER OFF state then sure you can do it but no BLE activity can be running during that time, you need to manage wake-up by some external GPIO interrupt line (button or some RTC capable chip if you expect to wake-up periodically).

[endnode]

Not really. Radio as such (the specific part of nRF5x SoC which does 2.4GHz radio Tx/Rx) is most of the time OFF. The call sd_ble_gap_adv_start is just function call from Soft Device (stack) API and you can be sure that stack isn't stupid to power radio all the time, it just runs RTC timer to wake it put for the shortest time necessary. So yes, by turning the advertisement off will safe some power but it will be only very little for these few missing Tx/Rx bursts of radio (typically up to 1.5ms per whole adv. interval, see charts in Soft Device specification) and the power to run RTC timer. If you want to count single adv. events then you have two options:

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