nrf_gpio_read_pin doesn't seem to be working

[LuGr]

I am trying to read if an input is 0 or 1 but for some reason it takes the first one its offered and then it does not change anymore.

int main(void)
{
   nrf_gpio_cfg_output(24);
        	
   nrf_gpio_cfg_input(26, NRF_GPIO_PIN_NOPULL);	

   for(;;)
   {      
      if(nrf_gpio_pin_read(26) == 1)
      {
         nrf_gpio_pin_toggle(24);
      }
   }
}

I've also tried to read the input into a variable like this in a while/for loop:

int value = nrf_gpio_pin_read(26);

But for some reason it keeps sticking to either the first value I stored in it or the direction of the pull up/down. I'm a bit at a loss at what to try as the problem seems wierd. I have tried multiple DKs and pins to ensure it wasn't faulty hardware.

EDIT: What i want to be able to do is make something happen depending on if the input is high or low at the moment I read this. It is connected to a comparator that puts either a digital 1 or 0 value on the pin I am using as input.

EDIT: After I thought it worked last time with the code that uses a button and led on the DK I gave the comperator another go but it starts acting up again that it sets the nrf_gpio_pin_read only once in a while/for loop. When I use the code below in combination with an external comperator and I hook the comperator up to a PSU it waits for the condition while(nrf_gpio_pin_read(26) > 0) once afterwards even if I lower the voltage so this is no longer true the blinky light remains.

nrf_gpio_cfg_output(21);
nrf_gpio_cfg_input(26, NRF_GPIO_PIN_NOPULL);

int main(void)
{
	nrf_gpio_pin_write(21, 0);
	nrf_delay_ms(5000);
	
	for(;;)
	{
		while(nrf_gpio_pin_read(26) > 0)
		{
			nrf_gpio_pin_toggle(21);
			nrf_delay_ms(500);
		}
		nrf_gpio_pin_toggle(24);
	}
}

[Einar Thorsrud]

I'm a bit uncertain about your code. If you execute it like you show, nrf_gpio_pin_read() is only called once, and so it is no wander that it never changes. Or do you call it in a loop, just that you did not include the code for it? If you can post more of your code or a better explanation we will not have to make so many assumptions, and it will be easier to find a good answer.

[Einar Thorsrud]

I do not see a problem with your code. Have you verified with a debugger or in another way that you always read the same value? I did a small modification to your code in order to run the code on the nRF51 DK and this code works for me:

#define BUTTON_1 17
#define LED_1 21

int main(void)
{
   nrf_gpio_cfg_output(LED_1);

   nrf_gpio_cfg_input(BUTTON_1, NRF_GPIO_PIN_PULLUP); 

   for(;;)
   {      
      if(nrf_gpio_pin_read(BUTTON_1) == 0)
      {
         nrf_gpio_pin_toggle(LED_1);
      }
   }
}

The intensity of the LED will be a bit dimmed when button 1 is pressed down, as the duty cycle of the LED will be 50% due to the toggling. When the button is not pressed the LED will either be off or glowing at 100%.

[LuGr]

I had verified the error with the debugger and an oscilloscope but after loading a couple of example projects using the read function it started to work. I am not sure what solved the problem eventually.

[Einar Thorsrud]

What is the voltage of the logical 0 and logical 1 out of your external comparator (in to the GPIO)? According to Section 8.23 in the Product Specification a logical high is between 0.7*VDD and VDD and a logical low is between VSS and 0.3 VDD.

[LuGr]

I've measured the comperator output and the logical high is 3.28V and the low is 0.01V. But after trying out some more pins I've found I can read the logical high and low with pin 10 not sure what the difference between it and the other pins is as I've yet to discern it from the product specifications.