NFC as GPIO on nRF52833

[Jonathan]

Using nRF52832, I've got some firmware that uses NFC pins (9 & 10) without problem, using CONFIG_NFCT_PINS_AS_GPIOS.

I'm now trying to replicate this using nRF52833, and I'm failing.

I used ble_app_blinky as a starting point (for PCA10056), and just put this in main():

    if ((NRF_UICR->NFCPINS & UICR_NFCPINS_PROTECT_Msk) == (UICR_NFCPINS_PROTECT_NFC << UICR_NFCPINS_PROTECT_Pos)){
            NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos;
            while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
            NRF_UICR->NFCPINS &= ~UICR_NFCPINS_PROTECT_Msk;
            while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
            NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos;
            while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
            NVIC_SystemReset();
    }

    for (int pin = 0; pin < 32; ++pin)
  {
    nrf_gpio_pin_dir_set(pin, NRF_GPIO_PIN_DIR_OUTPUT);
  }
  while (1)
  {
    for (int pin = 0; pin < 32; ++pin)
    {
      nrf_gpio_pin_set(pin);
    }

    nrf_delay_ms(1000);

    for (int pin = 0; pin < 32; ++pin)
    {
      nrf_gpio_pin_clear(pin);
    }

    nrf_delay_ms(1000);
  }
   

Note the first bit was added after, just to make sure the NFC pins are reprogrammed.

However, pin 9 & 10 still don't get toggled by this code.

Checking the value of NRF_UICR->NFCPINS, it's 0xFFFFFFFE, so I don't understand what's wrong... Thanks!

[Kenneth]

It may be that you some time in the past have programmed an application that have enabled NFC, hence the NFC pins have been set in UICR. I suggest that you execute an 'nrfjprog --erasell" from command lines to erase the UICR.

Kenneth

[Jonathan]

Thanks, I tried ("--eraseall") but that didn't change anything...

[Kenneth]

I think you should execute the 'nrfjprog --eraseall' and check by reading 'nrfjprog --memrd 0x1000120C --w 32 --n 4' when/if NFC pins are enabled at any time. They should not be enabled if you have added CONFIG_NFCT_PINS_AS_GPIOS in the preprocessor of your project.

Additional question; If you are using the nRF52840-DK, are you sure you have followed the description on the back side of the DK in terms of soldering bridges such that the GPIO's are connected to the header?

Kenneth

[Jonathan]

Reading memory returns:

0x1000120C: FFFFFFFE

(CONFIG_NFCT_PINS_AS_GPIOS is defined in the project, and I still have an extra copy of the code it triggers at the beginning of the project).

Is there anything else that controls NFC/GPIO pins?

[Kenneth]

Did you also see the last part of my comment:

Additional question; If you are using the nRF52840-DK, are you sure you have followed the description on the back side of the DK in terms of soldering bridges such that the GPIO's are connected to the header?

[Jonathan]

I'm using the nRF52833-DK, I can't see anything looking like instructions on the bottom side though (also if that matters, I've tried a variety of other GPIOs and they are working fine). Thanks for your help!

[Jonathan]

Thank you... I switched to the DK because I could easily put it on the scope.

After your answer, I switch backed to my board and it's actually working. I had just not tried on my board after re-enabling CONFIG_NFCT_PINS_AS_GPIOS .