How to trigger an task on a GPIO output from a GPIO input event

RE: How to trigger an task on a GPIO output from a GPIO input event

Oystein — Sun, 14 Sep 2025 17:08:55 GMT

I dont have any bootloader but solved it like this. With this code i can choose wether to have a software reset or hardware reset

//Button pins interface init
 NRF_P1->PIN_CNF[6] = 0x0000000C;     //Nrf52 button GPIO input pin port P1.06, internal pull up, STANDARD driveSENSE disabled
 NRF_GPIOTE->INTENCLR = 0x00000001;   //Disable interupts on CONFIG[0] pin
 NRF_GPIOTE->CONFIG[0] = 0x00122601;  //Set BUTTON press on port P1.06 as a GPIOTE EVENT to generate an interrupt event when going from HIGH to LOW.
 NRF_GPIOTE->EVENTS_IN[0] = 0;        // Clear any potential events that could have occured during configuration
 NRF_GPIOTE->INTENSET = 0x00000001;   //Enable EVENT interupts on UARTTE CONFIG[0] pin

 //nRF52 self RESET pin
 NRF_P1->OUTSET = 0x00000400;        //Set P1.10 GPIO output pin HIGH. 
 NRF_P1->PIN_CNF[10] = 0x0000000F;   //GPIO output pin port P1.10, internal pull up, STANDARD drive, SENSE disabled

 //Enable GPIOTE interrupt in NVIC
 NVIC_EnableIRQ(GPIOTE_IRQn);        // Enable GPIOTE interrupt in NVIC

//GPIOTE Interrupt handler
void GPIOTE_IRQHandler(void)
{
    if (NRF_GPIOTE->EVENTS_IN[0])   // Check if event on channel 0 fired
    {
        NRF_GPIOTE->EVENTS_IN[0] = 0;  // Clear event

        //Use only soft or hard reset
        //NVIC_SystemReset();            // 🔥 Force system soft reset
        NRF_P1->OUTCLR = 0x00000400;     // 🔥 Force system hard reset
    }
}

I am not 100% sure if myt understanding of SOFT and HARD RESET is coreect, but anyway both NVIC_SYSTEMRESET() or setting the P.1.10 LOW both ways will reset the MCU

Øystein

RE: How to trigger an task on a GPIO output from a GPIO input event

Vidar Berg — Tue, 09 Sep 2025 09:04:42 GMT

Hi Øystein,

[quote user="Oystein"]I also encountered a problem with my design. The PPI channel TASK OUT do not release the PIN and set it HIGH, its kept LOW so the MCU freezes. It do not work. I also tried to set up a second PPI channel to trigger a LOW_TO_HIGH on the GPIO pin 1.10 when the nRESET signal goes LOW. Not sure why, but did not work[/quote]

Are you testing with the output physically connected to the reset line?

[quote user="Oystein"]Anyway. as you point out, Is it not sufficient to perform a soft reset from your code. I think maybe I try that, but is there any code exapmles or guides on how I can trigger SOFT RESET triggered by a GPIO INTERRUPT event HIGH_TO_LOW on pin GPIO 1.6[/quote]

You can write '0xB1' (BOOTLOADER_DFU_START) followed by NVIC_SystemReset() in your button ISR to reset into bootloader DFU mode as long as the bootloader is built with NRF_BL_DFU_ENTER_METHOD_GPREGRET

Best regards,

Vidar

RE: How to trigger an task on a GPIO output from a GPIO input event

Oystein — Sun, 07 Sep 2025 18:59:19 GMT

Hi Vidar

I think you are correct, its uneccesary I think to use a GPIO and route it to the nRESET pin. It semmes like it has hostorically been designed that way for firmware upgrade over USB. USBDFU Trigger Lib need a GPIO that can control the physical "RESET pin

I also encountered a problem with my design. The PPI channel TASK OUT do not release the PIN and set it HIGH, its kept LOW so the MCU freezes. It do not work. I also tried to set up a second PPI channel to trigger a LOW_TO_HIGH on the GPIO pin 1.10 when the nRESET signal goes LOW. Not sure why, but did not work

Anyway. as you point out, Is it not sufficient to perform a soft reset from your code. I think maybe I try that, but is there any code exapmles or guides on how I can trigger SOFT RESET triggered by a GPIO INTERRUPT event HIGH_TO_LOW on pin GPIO 1.6

Øystein

RE: How to trigger an task on a GPIO output from a GPIO input event

Vidar Berg — Thu, 04 Sep 2025 11:52:57 GMT

Hi Øystein,

I'm not sure I like the idea of having a GPIO output connected directly to the reset line. Is it not sufficient to perform a soft reset from your code? Anyway, I took the liberty of updating your code to make it more readable, see below. The TEP or EEP or endpoint address was wrong.

#define BTN_INPUT   NRF_GPIO_PIN_MAP(1,6)
#define RESET_SIG   NRF_GPIO_PIN_MAP(1,10)


nrf_gpio_cfg_input(BTN_INPUT, NRF_GPIO_PIN_PULLUP);
NRF_GPIOTE->CONFIG[0] = (GPIOTE_CONFIG_MODE_Event << GPIOTE_CONFIG_MODE_Pos) |
                        (BTN_INPUT << GPIOTE_CONFIG_PSEL_Pos) |
                        (GPIOTE_CONFIG_POLARITY_HiToLo << GPIOTE_CONFIG_POLARITY_Pos);

NRF_GPIOTE->CONFIG[1] = (GPIOTE_CONFIG_MODE_Task << GPIOTE_CONFIG_MODE_Pos) |
                        (RESET_SIG << GPIOTE_CONFIG_PSEL_Pos) |
                        (GPIOTE_CONFIG_POLARITY_HiToLo << GPIOTE_CONFIG_POLARITY_Pos) |
                        (GPIOTE_CONFIG_OUTINIT_High << GPIOTE_CONFIG_OUTINIT_Pos);

NRF_PPI->CH[0].EEP = (uint32_t) &NRF_GPIOTE->EVENTS_IN[0];
NRF_PPI->CH[0].TEP = (uint32_t) &NRF_GPIOTE->TASKS_OUT[1];
NRF_PPI->CHENSET = 1;

Best regards,

Vidar