Taiyo Yuden EYSHJNZXZ (nRF52832) cannot use NFC pins as GPIO

[NewAce]

I am having trouble using GPIO P0_9 and P0_10 as GPIO pins. These are the pins designated as NFC1 and NFC2.

I am using the following sample code:

#include <stdbool.h>
#include <stdint.h>
#include "nrf_delay.h"
#include "boards.h"

/**
 * @brief Function for application main entry.
 */
int main(void)
{
    nrf_gpio_cfg_output(9);
    nrf_gpio_cfg_output(10);

    while (true)
    {
    nrf_gpio_pin_toggle(9);
    nrf_gpio_pin_toggle(10);
    nrf_delay_ms(500);
    }
}

I have confirmed that UICR 0x20C is set to 0xFFFFFFFE:

sh-3.2# nrfjprog --memrd 0x1000120c --family nrf52
0x1000120C: FFFFFFFE                              |....|

I can use any other pin for GPIO, except P0_9 and P0_10. Any insights as to what is going on, would be greatly appreciated.

[endnode]

Have you searched the forum, e.g. this question? The UICR settings is one thing but there could be some HW components on board. What the vendor says?

[NewAce]

I actually found the issue (see my comment above). The Taiyo Yuden module includes a 32MHz crystal and a few capacitors under the hood and has a built-in Bluetooth antenna. It is a fully certified module. It does not have a 32kHz crystal, but the GPIO9/10 pins are exposed directly from the nrf52832 chip, so nothing unexpected.