How to connect nrf9160 with multiple bme280 sensor?

[PoNien Su]

Hello!

I have followed nrf connect sdk tutorial part3 and have walked through for bme280. But now I want to connect two or more bme280 sensors to my dk. How should I modify the prj.conf file, the overlay file and the main.c file?

Thanks a lot.

Regards

PoNien Su

[Albrecht Markus Schellenberger]

Hello PoNien Su,

Here is an example of how you can connect three BM280 sensors to the nRF9160 DK using the I2C-interface.

Since the device addresses of the BME280 are limited to 0x76 and 0x77, you can connect two sensors to one I2C-bus and the third to an additional one.

Your overlay file will then look like this:

&i2c2 {
	bme280_76@76 {
		compatible = "bosch,bme280";
		reg = <0x76>;
		label = "BME280_76";
	};
	bme280@77 {
		compatible = "bosch,bme280";
		reg = <0x77>;
		label = "BME280";
	};
};

&i2c3 {
	sda-pin = < 0x12 >;
	scl-pin = < 0x11 >;
	compatible = "nordic,nrf-twim";
	status = "okay";	
	bme280_i2c3@77 {
		compatible = "bosch,bme280";
		reg = <0x77>;
		label = "BME280_I2C3";
	};
};

&spi3 {
	status = "disabled";
};

Be aware that due to memory instantiation, you have to disable the SPI3 interface. See:

https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf9160%2Fmemory.html&anchor=topic

Make sure that you are using the following options in prj.conf:

 

CONFIG_I2C=y
CONFIG_SENSOR=y
CONFIG_BME280=y

You can now use the sensors in main.c in the same way as demonstrated in the tutorial.

I hope this will help you! Let me know if you have any more questions.

Regards,

Markus

[PoNien Su]

Hello Marcus,

Thanks for your answer and it really helps me a lot., but now I meet another problem.

When I followed the steps and trying to create the forth I2C-bus in overlay file, it didn't allow me to complete CMake.

Does it mean that I could only connect 6 bme280 sensors to nrf9160dk? Or is there any solution that can help me to connect up to 30 bme280 sensors to my dk since there are 31 pins on it?

Sorry for bothering again.

Regards,

PoNien Su

[Albrecht Markus Schellenberger]

As you can see in the memory instantiation, the nRF9160 has four I2C peripherals. Considering the address limitation of the BME280, that means you can connect up to 8 BME280 sensors to it. But then you have to make sure that the other peripherals using the same memory instantiation are disabled, which probably is the reason why CMake didn’t complete.

If you would like to connect more than 8 sensors, you have to switch over to the SPI peripheral or use it in combination with I2C. But even there the number of devices you can communicate with is limited to under 30, depending on the design of the chip select.

Regards,

Markus

[AMG]

Hi,

What firmware version are you using ?

Kind regards,

-Ahmed

[Albrecht Markus Schellenberger]

Hello Ahmed,

Do you mean the modem firmware of the nRF9160 or which version of the nRF Connect SDK?

Regards,

Markus