Questions on configuring the PIN to connect to sensor LPS22HB

[Botong Ou]

Hi everyone,

I am new to programming on such an embedded device(NRF52840DK). I met a problem recently of how to set up the PIN on the board to connect with the LPS22HB sensor.

Basically, I am sure that only 3.3V, GND, SDA, SCL on the sensor is required to be connected(I2C communication). And I am using Zephyr as the underlying RTOS. Here are my questions:

1. Currently, I don't have a breadboard so I am wondering if I could use some pins like P1.07 and P1.06 as the 3.3v and GND respectively.

2. I found out that NRF52840DK only have a 5v pin, then how can I set up a 3.3v pin

3. To use SDA and SCL, I need to create an overlay file. I followed some examples and create a simple file like this and I have some problems:

&i2c0 {
        status = "okay";
        //Here I am confused about how to distinguish between P1 and P0
        sda-pin = <4>;  //Refer to P1.04 or P0.04 on board?
        scl-pin = <5>; //Refer to P1.05 or P0.05 on board?
        
        lps22hb@76 {
                //I don't know how to select the compatible name
                compatible = "nordic,lps22hb";
                //This address is from the sensor or the board?
                reg = <0x76>;
                label = "LPS22HB";
        };
};

1. How to distinguish between P1 and P0 in the overlay file

2. Do we need to follow some standards to specify the compatible field?

3. How to get the address in the reg field

Again, there might be lots of stupid questions here but I honestly can't find a sufficient guide for beginners. 

I appreciate it if someone can answer these questions. Thanks in advance.

[Kenneth]

Hi,

You should use proper GND and VDD to the sensor, avoid using GPIO's as "power and ground". For instance on the nRF52840-DK there should be pins labeled VDD (this is approx ~3V) and GND that you can use to power external sensor.

1. Looking at the implementation of nrf_gpio.h I can see that port1 will simply be after port0:
https://github.com/nrfconnect/sdk-hal_nordic/blob/master/nrfx/hal/nrf_gpio.h#L523

So to use P1.00 you simply set <32>, and P1.01 you simply use <33>.

2. I suggest to look at the sample applications that use the drivers you are interested in. But if you want to learn more check out:
http://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/guides/dts/howtos.html

3. You need to refer to the datasheet for the specific sensor, the i2c address should be specified there (sometimes there may be 2 addresses to choose between depending on how the pins for the sensor is set).

Kenneth

[Botong Ou]

Thank you very much, let me check them out.