Not able to detect GPIO state, reading incorrect GPIO pin value

[RO]

Hello,

I am working on a custom board using a nRF52840 based module. I am using SDK 14.2

I am running the following simple code to sense when an GPIO goes to a low state(detects SD card insertion) and toggle an LED.

GPIO P0.13 is connected to a SD card detect pin which gets grounded if an SD card is inserted, else it is left floating.

GPIO P0.15 is connected to an anode of an LED. 

int main(void)
{
    nrf_gpio_cfg_input(13, NRF_GPIO_PIN_PULLUP);
    nrf_gpio_cfg_output(15);
    uint32_t new_CD;
    while (true)
    {
        new_CD = nrf_gpio_pin_read(13);
	if (new_CD == 0) {
		
                nrf_gpio_pin_toggle(15);
		}
        // Do nothing.
    }
}

However, the controller does not detect a low state on P0.13, when I insert the SD card. I have verified that the pin is indeed grounded using a oscilloscope.

During debugging, the 'new_CD' variable on the watch window is also always '1'.

Why cant I detect a low state on the GPIO correctly?

Thanks

[Susheel Nuguru]

If the pin P0.13 is actually going low when SD card is inserted then I guess the compiler is optimizing away the code around new_CD. I would suggest you to use volatile for new_CD since the way you wrote code gives compiler great flexibility to optimise code. Also set optimizations low or none while testing this.

Suggestion to change declaration of new_CD like below

   volatile uint32_t new_CD;

[RO]

volatile did not work.

Although using the same code(even without volatile) works on a DevKit.

Any idea why?

[Susheel Nuguru]

Then it only points out to something being wrong on your custom board. I suggest you to check again the schematics of it. You can send the schematics and board layout files to us so that we can get it reviewed by our hardware experts in support.