Start and stop RTC with PORT events on a single pin

[haakonsh]

Hi, i'm wondering if it's possible to make a GPIO pin trigger different tasks when it is externally driven from low to high, and high to low.

I'm trying to stop an RTC timer when a pin goes high and start it again when it goes low, using PPI. Do i need to allocate two GPIOTE channels? And how do i get the different event adresses?

I'm on the nRF52, and i'm not using SD, I also don't want the high frequency clock running.

[Paul]

Yes, you can do this no problem. and you need to use GPIOTE. I guess you are capturing pulse width using RTC?

[Paul]

Sorry, I didn't see nRF52 in your message. I haven't used 52 a lot. But I think it is the same concept: Are you having problem using single pin for two tasks? I solved this issue by some tricks in nRF51 SDK: You need to use a "unused/fake" pin as a channel placeholder to hold the other channel for the "real" pin. and then change the "fake" pin back to the "real" pin by using nrf_gpiote_event_configure.

[Paul]

Probably in the next SDK release Nordic can remove this limitation? :-)

[haakonsh]

I'm trying to halt the execution of code which is periodically called with the RTC, using an external interrupt.

Do i use the placeholder pin when i run nrf_drv_gpiote_in_event_addr_get(placeholder) when assigning EEP and TEP to a ppi channel?

exp: APP_ERROR_CHECK(nrf_drv_ppi_channel_assign(ppi_channel_rtc_start, nrf_drv_gpiote_in_event_addr_get(ADXL362_INT_PIN), nrf_drv_rtc_task_address_get(&rtc, NRF_RTC_TASK_STOP)));

edit: It seems that nrf_gpiote_event_configure is only valid when GPIOTE is in high accuracy mode (using hfclk), otherwise it is using: m_cb.port_handlers_pins[channel-NUMBER_OF_GPIO_TE] |= (p_config->sense)<< SENSE_FIELD_POS;

The control block is locked static in the driver, so i don't have access to it.