PPI Timer2 weird behavior on Bluetooth connect

[technicc]

Hello!

We're using PPI to connect one pin to clear and capture events on Timer2. On pin low-to-high we're clearing the timer and on pin high-to-low, we're capturing the timer. We have S110 enables and inited on PCA10001 board.

The application works great until we connect the PCA10001 to the PCA10000 (via master control panel) at which moment the values from the timer become erratic and random. It stays the same after Bluetooth disconnect.

[Susheel Nuguru]

There should be a GPIOTE involved in the usecase you mentioned. GPIOTE will convert the pin state change into events, which should be connected to PPI to convert into a timer task. After configuration there is no software involved in clearing and capturing the timer value. It is done by hardware so S110 connections and disconecctions shall not effect this.

1)Did you use different GPIOTE and PPI channels to configure the pin state change? 2) how are you reading these values, is your reading interrupt based?If your processing time for your interrupt is less than 100us, you could set the interrupt priority to APP_HIGH to see if that helps. 3)If pin state change is happening faster than the softdevice is allowing the app to read it then it is possible that after connection (softdevice blocks cpu for 1ms-6ms depending on packet length) then you are missing few read cycles of timer capture register.

[technicc]

We're not using an interrupt handler, we're just reading the captured value of the timer in the main while(1) loop. This is the relevant code:

nrf_gpiote_event_config(2, 10, NRF_GPIOTE_POLARITY_LOTOHI);        
nrf_gpiote_event_config(3, 10, NRF_GPIOTE_POLARITY_HITOLO);

sd_ppi_channel_assign(2, &NRF_GPIOTE->EVENTS_IN[2], &NRF_TIMER2->TASKS_CLEAR);
sd_ppi_channel_enable_set(1 << 2);
sd_ppi_channel_assign(3, &NRF_GPIOTE->EVENTS_IN[3], &NRF_TIMER2->TASKS_CAPTURE[0]);
sd_ppi_channel_enable_set(1 << 3);

In the main while(1) we're reading the value periodically like this:

counter = NRF_TIMER2->CC[0];

We did a bit more playing around though ... If we assign channels on PPI (last four lines at the top) AT bluetooth connect (case BLE_GAP_EVT_CONNECTED), it seems to be working fine.

Does the soft-device stack change PPI channels (channels 2 and 3) on Bluetooth connect?