I2C or SPI bridge between nrf9160 and nrf52840 (Thingy91)

[albdom]

Hello

I am developing a prototype with the Thingy 91 that allows to have the default log in the UART0 <-> USB and collect the data of a sensor through the P6 expansion port (nrf52 SPARE) through the UART1 of the nrf52840.
I need a bridge to share the sensor data between the nrf52840 and nrf9160 but I run into the problem that the two available UART instances are already busy. My question is if it is possible to bridge via I2C or SPI on the shared MCU_IF pins. For the nrf52840 code I am relying on the usb_uart_bridge example.

Thx!

[Øyvind]

Hello,

For the nrf52840 code I am relying on the usb_uart_bridge example.

 Please note that the usb_uart_bridge sample has an improved application, called Connectivity Bridge, which also introduces the Nordic UART Service (NUS).

 

My question is if it is possible to bridge via I2C or SPI on the shared MCU_IF pins.

 Yes, you should be able to use MCU_IF pins for this purpose.

Kind regards,
Øyvind

[albdom]

Thanks for the reply Øyvind. Is there an example with I2C for the nrf52840? In the sdk connect I can't find anything related to this microprocessor

Thx!

[Øyvind]

You are right, there aren't that many examples of I2C on the nRF52840 in the nRF repository of the nRF Connect SDK. There are some samples in the Zephyr repository that may focus more on I2C, and that should work on the nRF52840 e.g. the sensor samples have I2C examples that work with nRF52840 e.g. the BME280 humidity and pressure sensor sample

Hope this is of some help :)

[albdom]

Following the example of zephry's BME280 sensor I get a compilation error: zephyr No SOURCES given to target: drivers__i2c

I have also tried to communicate with the i2c driver of nrf (twi) but I get compilation errors like: error: 'DT_NORDIC_NRF_TWI_I2C_0_CLOCK_FREQUENCY' undeclared

The nrf52840_pca20035.dts file:

&i2c0 {
	status = "okay";
	compatible = "nordic,nrf-twim";
	sda-pin = <25>;
	scl-pin = <22>;
	clock-frequency = <I2C_BITRATE_STANDARD>; 
};

The prj.conf file:

CONFIG_I2C=y
#CONFIG_SENSOR=y
CONFIG_I2C_NRFX=y
CONFIG_I2C_0=y
CONFIG_I2C_0_NRF_TWI=y
CONFIG_I2C_INIT_PRIORITY=60

[Øyvind]

Have you configured correct address for the sensor? In the zephyr\samples\sensor\bme280\boards\nrf52840dk_nrf52840.overlay

&i2c0 {
	bme280@77 {
		compatible = "bosch,bme280";
		reg = <0x77>;
		label = "BME280";
	};
};

You must edit reg to correct i2c address. For my part it was 76 which was the correct address. 

Kind regards,

Øyvind

[albdom]

Thanks for the info!

Only that my goal is to enable an I2C for the nrf52840_pca20035 board, not the nrf52840dk_nrf52840

[Øyvind]

My apologies for not being clear. 

You can copy nrf52840dk_nrf52840.overlay to your project folder and rename to nrf52840_pca20035.overlay Depending on what NCS version you are on, make sure to use correct board name. From NCS v1.3.0 the board names of Thingy:91 were changed to: thingy91_nrf9160 and thingy91_nrf52840. What version of NCS are you working on?

You can also copy the content of nrf52840dk_nrf52840.overlay and add to your nrf52840_pca20035.dts. The former will concatenate and add/overwrite settings to &i2c0, adding the bme280 as a child node to your &i2c0, providing a zephyr.dts that will look similar to:

&i2c0 {
	status = "okay";
	compatible = "nordic,nrf-twim";
	sda-pin = <25>;
	scl-pin = <22>;
	clock-frequency = <I2C_BITRATE_STANDARD>; 
	bme280@77 {
		compatible = "bosch,bme280";
		reg = <0x77>;
		label = "BME280";
	};
};