SHT31 readout on nRF5340 using the Zephyr Sample

[makoto.inoue]

Hi everyone,

I am trying to get the Zephyr SHT31 sample running on a nRF7002-DK (nrf5340), but I only get "Device SHT3XD is not ready".

I ran a debug session, and it is failing due to zephyr/kernel/device.c::z_device_is_ready funcition returning false.

somehow the dev->state->initialized = true, but dev->state->init_res = 5 (needs to be 0 for the function to return true).

My guess is that I need to fix my device overlay file - below is the device overlay file I am using:

&i2c1 {
	sht3xd@44 {
		compatible = "sensirion,sht3xd";
		reg = <0x44>;
		label = "SHT3XD";
	};
};

Thanks!

Makoto

[Sigurd Hellesvik]

Hi,

Have you enabled I2C in prj.conf?

Your driver should be enabled in the devicetree overlay with

status = "okay";

Regards,
Sigurd Hellesvik

[makoto.inoue]

Hi Sigurd,

Thank you for your help.

Yes, I have enabled I2C in prj.conf. Below is my prj.conf:

CONFIG_STDOUT_CONSOLE=y
CONFIG_I2C=y
CONFIG_SENSOR=y
CONFIG_CBPRINTF_FP_SUPPORT=y

I've tried with status = "okay"; added to the overlay file:

&i2c1 {
	sht3xd@44 {
		compatible = "sensirion,sht3xd";
		status = "okay";
		reg = <0x44>;
		label = "SHT3XD";
	};
};

But I still get the same problem in device.c (line 103): dev->state->init_res = 5

FYI the same hardware setup works (I get both temperature and humidity readouts) with nRF52840DK.

Also I am using the code from here:

https://github.com/zephyrproject-rtos/zephyr/blob/main/samples/sensor/sht3xd/README.rst

In the above documentation, I see an entry:

"Depending on the baseboard used, the SDA and SCL lines require Pull-Up resistors."

Would I need pull-up resistors when working with nRF7002DK board (nRF52840DK works with the same setup)?

Thanks,

Makoto

[makoto.inoue]

Hi Sigurd,

Thank you for the info.

Last night I realized a critical error I made - nRF7002DK VDD is 1.8v (I assumed 3v). nRF52840DK is 3v. the SHT31-D board I am using requires at least 2.4v to turn on. This likely explains why nRF52840DK worked and nRF7002DK does not.

I ordered a level shifter today, so whenever I receive it I will test it out and post the result here. 

[Sigurd Hellesvik]

Ah yes, I agree.
This is likely the issue here.

Good find!

[makoto.inoue]

Hi Sigurd,

I can confirm that level shifter for the I2C solved the problem! I am getting the sensor readings now.

The board overlay file ended up being:

&i2c1 {
    sht3xd@44 {
		compatible = "sensirion,sht3xd";
		reg = <0x44>;
	};
};

As a side note, I did have to try two different level shifters. Somehow PCA9306 based level shifter didn't work (maybe I got a dud one), but FXMA2102 based level shifter worked... 

Anyway, thank you for your help!

Best Regards,

Makoto

[makoto.inoue]

Dear Nordic team, I think this ticket can be closed.

I realized that I have few more tickets that probably should be closed (they have "Verified Answer" check).

Do I ask it to be closed, or just let it go? Just curious what it should be...

[Sigurd Hellesvik]

Verified Answer is equivalent to Closed, so that is good.
Thanks!