P0.09 and P0.10 as GPIO (nRF52832 + IAR + custom board)


I know this issue has been discussed extensively in different posts, and I believe I read all of them, but still I can't get it working. 

I'm trying to drive three LEDs on pins P0.09, P0.10 and P0.11 of an nRF52832 on a custom board, using IAR as IDE. The LED connected to PIN 11 works fine, but the others don't. I understand these two are pins dedicated to the NFC functionality, and they require the last bit of NFCPINS to be set to 0 if you want to run them as GPIO. 

(I know if using the DK, there is a HW issue regarding a couple of missing resistors, but that's not my concern since I am using my own board, and PINS 9 and 10 are connected directly to the LEDs circuit.)

I tried to add this line of code in "uicr_config.h":

const uint32_t UICR_ADDR_0x20C    __attribute__((at(0x1000120C))) __attribute__((used)) = 0xFFFFFFFE;

But it didn't solve the problem. Besides, I'm getting a warning about the "at" attribute, but maybe that's not an issue, since it's actually not an error...(?)

I have included the "uicr_config.h" file in my libraries and I have defined "CONFIG_NFCT_PINS_AS_GPIOS" in my "main.c", but no luck yet. 

Can anyone suggest other things to try, please? 

Many thanks! 

  • Adding the CONFIG_NFCT_PINS_AS_GPIOS is correct, but not in main.c. Instead in IAR add this macro in Options->C/C++ Compiler->Preprocessor->Defined Symbols

    This macro is then applied in system_nrf52.c the first time power is applied thus:

        /* Configure NFCT pins as GPIOs if NFCT is not to be used in your code. If CONFIG_NFCT_PINS_AS_GPIOS is not defined,
           two GPIOs (see Product Specification to see which ones) will be reserved for NFC and will not be available as
           normal GPIOs. */
        #if defined (CONFIG_NFCT_PINS_AS_GPIOS)
                NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos; // Write Enable
                while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
                while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
                NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos; // Read-only Enable
                while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
                // UICR changes require a reset to be effective

  • Thank you for your reply! I have added CONFIG_NFCT_PINS_AS_GPIOS in the Defined Symbols as you suggested, but it still doesn't work. Could it be something else? 

  • I got it working by calling SystemInit(); in my main.c

  • Good news, but SystemInit() should already have been called from within iar_startup_nrf52.s:

            DCD     sfe(CSTACK)
            DCD     Reset_Handler
            LDR     R0, =SystemInit
            BLX     R0
            LDR     R0, =__iar_program_start
            BX      R0

    Have you used a different Reset_Handler?