nRF52840 configure P0.0 and P0.1 as GPIO

[Nhuan]

Hello,

I would like to use P0.0 and P0.1 as General GPIO for I2C in nRF52840.

I have run the twi_sensor example in SDK 17, it works well with ARDUINO_SCL_PIN and ARDUINO_SDA_PIN, but when I set 

.scl                = NRF_GPIO_PIN_MAP(0, 1),

.sda               = NRF_GPIO_PIN_MAP(0, 0),

the transmission isn't success.

May I ask how can I configure P0.0 and P0.1 as GPIO for TWI (I'm using nRF52840 DK)?

Thank you!

[Jørgen Holmefjord]

Hi,

The P0.00/P0.01 pins are by default connected to the 32.768 kHz crystal on the nRF52840 DK, and disconnected from the pin headers. If you want to use the pins as GPIOs, you can disconnect the crystal as described in the documentation: 32.768 kHz crystal.

Also make sure that you change the LFCLK source from XTAL to RC if you use the LFCLK in your application (always used by SoftDevice if this is enabled for BLE).

Best regards,
Jørgen

[Jørgen Holmefjord]

As long as you do not start the LFCLK, you can use the pins as GPIOs. If you start the LFCLK, you need to set the LFSRC to RC.

On a custom board where you do not have the 32.768 kHz crystal mounted, you can use the pins for TWI without modifications to the board. The modification is required on the DK, since we have included an option to disconnect the crystal if it is not required. This makes the DK flexible for multiple configurations.