NFC as GPIO

RE: NFC as GPIO

awneil — Wed, 17 Apr 2019 14:26:19 GMT

Documentation links here:

https://devzone.nordicsemi.com/f/nordic-q-a/37682/po-09-configure-as-digital-input-button/182644#182644

RE: NFC as GPIO

hmolesworth — Thu, 01 Nov 2018 15:15:33 GMT

The solution you propose should only be used if a bit requires changing, and not on every reset.

Be aware of nWRITE. The UICR register is part of the Flash memory, and it must not be repeatedly written (max 181 times) as it would be by an indiscriminate register write in user code on every reset. The Nordic SystemInit() checks the value before writing when using the defines to avoid repeated writes. This also means - for example - that the NFC pins can not be easily repeatedly switched between NFC mode and I/O port mode.

I quote:

"11.3 Writing to user information configuration registers (UICR)
User information configuration registers (UICR) are written in the same way as Flash. After UICR has been written, the new UICR configuration will only take effect after a reset.
UICR can only be written nWRITE number of times before an erase must be performed using ERASEUICR or ERASEALL."

nWRITE,BLOCK Amount of writes allowed in a block between erase 181

RE: NFC as GPIO

cprehn — Thu, 01 Nov 2018 13:19:20 GMT

I found a solution that worked for me. I put this code block in the main function. I found it here.

/* MWU Enable -- This is workaround suggested by Aryan on the Nordic Developer Zone */
NRF_MWU->REGIONENSET
    = ((MWU_REGIONENSET_RGN0WA_Set << MWU_REGIONENSET_RGN0WA_Pos) 
     | (MWU_REGIONENSET_PRGN0WA_Set << MWU_REGIONENSET_PRGN0WA_Pos));

/* Turn on flash write enable and wait until the NVMC is ready: */
NRF_NVMC->CONFIG = (NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos);
while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}

/* write to the register */
NRF_UICR->NFCPINS = 0xFFFFFFFE;
while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
    
/* Turn off flash write enable and wait until the NVMC is ready: */
NRF_NVMC->CONFIG = (NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos);
while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
    
/* MWU Disable -- This is workaround suggested by Aryan on the Nordic Developer Zone */
NRF_MWU->REGIONENCLR
    = ((MWU_REGIONENCLR_RGN0WA_Clear << MWU_REGIONENCLR_RGN0WA_Pos) 
     | (MWU_REGIONENCLR_PRGN0WA_Clear << MWU_REGIONENCLR_PRGN0WA_Pos));

RE: NFC as GPIO

cprehn — Wed, 31 Oct 2018 16:33:22 GMT

P0.09 and P0.10: The NFC pins can be assigned for any other purpose provided their setup is changed. A permanent shunt exists between these pins to protect the nRF52 from damage when used for NFC. To minimize leakage current, ensure these two pins are at the same level when not in use.

Got that from here. I haven't seen anything from Rigado that mentions a way to change the hardware, but they imply that the pins are still usable as GPIO.

RE: NFC as GPIO

awneil — Wed, 31 Oct 2018 16:25:11 GMT

[quote userid="71764" url="~/f/nordic-q-a/40045/nfc-as-gpio"]I'm using the Rigado BMD-350-A[/quote]

Have you checked the Rigado documentation to see if their particular hardware implementation would affect this?