How to enable P0.09 and P0.10 as GPIO pins on the nRF52 instead of NFC pins?

[singh]

Hi,

I'm using nrf52 custom board designed for our project,For this we have P0.09 and P0.10 as rx and tx used for uart, when i configured this two pins as rx and tx it is not showing any data on the uart.I have read the datasheet and i have seen this link devzone.nordicsemi.com/.../
but i'm not able to resolve the problem ,please help me ASAP.

Regards,

Prudhvi.

[Rene]

Hi Eliot, I just wanna know whether you fix this problem or not. I encounter the same issue. P0.09 is used as UART RX pin. It always reports "APP_UART_COMMUNICATION_ERROR" after initialization. CONFIG_NFCT_PINS_AS_GPIOS CFLAG is defined. I checked the NRF_UICR->NFCPINS register, it is 0xFFFFFFFE.

[Eliot Stock]

(Your post should have been a comment, not an answer, btw). Yes, I got it working. Confirm you're using CFLAGS += -DCONFIG_NFCT_PINS_AS_GPIOS in the Makefile, not just a #define CONFIG_NFCT_PINS_AS_GPIOS (1) in the code. If you can, get the UART working on some other pins first to validate your code, then move it onto these pins. Or run the UART example app, but with the pins changed and the CFLAG added. Or find the point where CONFIG_NFCT_PINS_AS_GPIOS is used in the SDK and put in an #error Foo to confirm the preprocessor is including that code.

[hmolesworth]

As a guide, it's best to use the Nordic project-level defines as listed for NFC and Reset pins, as 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 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

[noob_with_ucontrollers]

Hi Eliot Stock I am going through the same issue. I defined CONFIG_NFCT_PINS_AS_GPIOS in the project preprocessor definitions and I added CFLAGS += -DCONFIG_NFCT_PINS_AS_GPIOS to my project makefile. I still think my pin 9 is causing troubles (it's pegged to 3.3V). 

How do I make sure the registers are being set by the code ? Do I have to add the line #include uicr_config.h anywhere in my main.c code?  

[bjorn-spockeli]

You can check that the correct value has been written to the UICR register using nrfjprog, i.e. 

nrfjprog --memrd 0x1000120C

which will return

0x1000120C: FFFFFFFE |....|

If the NFCPINS register is configured to use the NFC pins as GPIOs.