ON/OFF Led with PULL_UP/NO_PULL resistance

[cacaomeravigliao]

Hi everyone,
I have a custom board using nRF52832 chip.

I want to turn ON and OFF a LED, which is directly connected to a GPIO pin.

Using this configuration I expect that passing the following instruction to set it as an output

#define LED   NRF_GPIO_PIN_MAP(0,10)
nrf_gpio_cfg_output(LED);

and the following instruction

nrf_gpio_pin_set(LED);

the LED will turn ON, but this doesn't happen.
Otherwise, I have discovered that it turns ON if I use the internal Pull Up resistor:

nrf_gpio_cfg(LED,
             NRF_GPIO_PIN_DIR_OUTPUT,
             NRF_GPIO_PIN_INPUT_DISCONNECT,
             NRF_GPIO_PIN_PULLUP,
             NRF_GPIO_PIN_S0S1,
             NRF_GPIO_PIN_NOSENSE);

and it turns OFF when I disconnect the Pull Up resistor:

nrf_gpio_cfg(LED,
             NRF_GPIO_PIN_DIR_OUTPUT,
             NRF_GPIO_PIN_INPUT_DISCONNECT,
             NRF_GPIO_PIN_NOPULL,
             NRF_GPIO_PIN_S0S1,
             NRF_GPIO_PIN_NOSENSE);

I'm not understanding this behavior..

The nRF52832 chip is supplied by 3.3V and I should get 3.3V at GPIO pin when the LED is ON, but I get just 2.7V.

Is there some reason that explain these strange behaviors?

[Simonr]

Hi

First of all, P0.10 is set as an NFC pin by default in the nRF52832. You'll have to set NFC pins as GPIOs in order to use P0.10 and P0.09 as GPIOs. You can see how to do so here. Please also note that if you use the NFC pins as normal GPIOs, they are limited to lower frequencies than other GPIOs, and thus it might not work as you want it to. I recommend using any GPIOs except these and the Low drive, Low-frequency pins for this kind of "work".

Best regards,

Simon

[cacaomeravigliao]

Perfect! Now it works as expected!

I configured in preprocessor the define CONFIG_NFCT_PINS_AS_GPIOS and the two pins have been configured as GPIO.

Thank you!!