RADIO_IRQHandler called twice in quick succession

[m.wagner]

While investigating my stack corruption issue, I noticed that the RADIO_IRQHandler is always called twice in quick succession:

But the NRF_RADIO->INTENSET register only has the DISABLED interrupt listed as activated., but only within the first call of the RADIO_IRQHandler the DISABLED event was detected. What else could trigger this behaviour?

[m.wagner]

Okay, I just noticed that this piece of code usually gets called in the first call to RADIO_IRQHandler:

    NRF_RADIO->SHORTS = m_radio_shorts_common;
    update_rf_payload_format(m_config_local.payload_length);
    NRF_RADIO->PACKETPTR = (uint32_t)m_rx_payload_buffer;
    NRF_RADIO->EVENTS_DISABLED = 0;
    NRF_RADIO->TASKS_DISABLE = 1;

    while (NRF_RADIO->EVENTS_DISABLED == 0);

    NRF_RADIO->EVENTS_DISABLED = 0;
    NRF_RADIO->SHORTS = m_radio_shorts_common | RADIO_SHORTS_DISABLED_TXEN_Msk;

    NRF_RADIO->TASKS_RXEN = 1;

I assume this has to do with the double trigger?

This code forces the radio to stop if no valid packet has been received, because the SHORTS-configuration would put the RADIO in TX state at this moment.

So, I assume that the fact, that the radio is disabled again and the events register is cleared results in the Interrupt being pended and the handler being executed immediately after.

I tried disabling the DISABLED interrupt during this operation and re-enabling it before starting the radio, but to no avail.

Is there a way to achieve the same behaviour as outlined above (i.e. forcing the readio to stop) without the interrupt being pended?

[m.wagner]

It looks like calling NVIC_ClearPendingIRQ(RADIO_IRQn) before re-enabling the radio indeed does the trick.