How to use I2C on nRF52840 Dongle ?

[rickygai]

Hi,

I am not sure whether there is I2C pins on nRF52840 Dongle board as based on the Adafruit Feather nRF52840 Express the pin is P0.11 and P0.12 as shown below:
SCL 0.11 and SCK 0.14 are at the back of the nRF52840 Dongle but SDA 0.12 is missing from the nRF52840 Dongle board.





There is a Youtube link shown the use of I2C display with nRF52840 Dongle but lacking explanation.

https://www.youtube.com/watch?v=vJUrG41tYFw


I am new to Nordic nRF52840 Dongle board and trying to support it under Arduino platform, but found out many missing important protocol pins.
Otherwise, I will just use Adafruit Feather nRF52840 Express.

May I know is the pin number held on Nordic nRF52840 (eg. 0.11) and on the schematic diagram (SCL P0.11) from Adafruit nRF52840 Express the same ?

Please advise.

[Kazi Afroza Sultana]

Hello Ricky,

We do not have any examples with Arduino code. 

I would like to refer you to use Nordic nRF5 SDK ( for downloading the nRF5 SDK follow this link: http://developer.nordicsemi.com/nRF5_SDK/nRF5_SDK_v17.x.x/)  and can look at the TWI example (https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v15.0.0%2Ftwi_sensor_example.html) . There are two twi examples which you should be able to use as reference, e.g. \twi_scanner and \twi_sensor, the pins used by twi is controlled by defines and can be changed where you see best fit:

void twi_init (void)
{
ret_code_t err_code;

const nrf_drv_twi_config_t twi_lm75b_config = {
.scl = ARDUINO_SCL_PIN,
.sda = ARDUINO_SDA_PIN,
.frequency = NRF_DRV_TWI_FREQ_100K,
.interrupt_priority = APP_IRQ_PRIORITY_HIGH,
.clear_bus_init = false
};

err_code = nrf_drv_twi_init(&m_twi, &twi_lm75b_config, twi_handler, NULL);

APP_ERROR_CHECK(err_code);

nrf_drv_twi_enable(&m_twi);

}

Regarding pin selection: One thing I would like to add (what I did not mention in my previous reply) regarding using of GPIO pin (any) as 12C. It is recommended not to select the pin close to the radio ( these are marked as low frequency I/O, you can see in the pinout documentation).  But if there is no plan to communicate simultaneously then it should not be a problem. you can find pin assignment here in this link Nordic Semiconductor Infocenter. 

You also look at this tutorial to start with nRF52840 dongle https://devzone.nordicsemi.com/guides/short-range-guides/b/getting-started/posts/nrf52840-dongle-programming-tutorial . It was written on 2018 and still relevant. 

Hope it helps.

Best Regrads,

Kazi Afroza Sultana