I2C functions don’t work, but using the I2C shell does

RE: I2C functions don’t work, but using the I2C shell does

j_a536 — Mon, 11 Aug 2025 19:41:10 GMT

Sorry for the late reply. I couldn't compile your sample, so I wasn’t able to test it. But don’t worry, I tried doing the same using Rust to rule out any issue related to NCS. This way, I discovered that scanning I2C devices before trying to communicate with the sensor did the trick (Yes, it seems like a hardware-related issue.). So, back in NCS, I added zephyr,deferred-init; in the devicetree:

&i2c1 {
	status = "okay";
	pinctrl-0 = <&i2c1_default>;
	pinctrl-1 = <&i2c1_sleep>;
	pinctrl-names = "default", "sleep";

	lis2dh: lis2dh@19 {
    status = "okay";
		compatible = "st,lis2dh";
		reg = <0x19>;
		irq-gpios = <&gpio0 6 GPIO_ACTIVE_HIGH>,  <&gpio0 7 GPIO_ACTIVE_HIGH>;
		zephyr,deferred-init;
	};
};

I2C devices scan and sensor intialization:

const struct device *dev = device_get_binding("i2c@40004000");

if (dev == NULL) {
  printk("No device found\n");
  return;
}

for (uint8_t addr = 0x03; addr <= 0x77; addr++) { //scan this range is sufficient
  struct i2c_msg msg;
  uint8_t dummy;

  msg.buf = &dummy;
  msg.len = 1;
  msg.flags = I2C_MSG_WRITE | I2C_MSG_STOP;

  int ret = i2c_transfer(dev, &msg, 1, addr);

  if (ret == 0) {
    printk("Device found at 0x%02x\n", addr);
  }
}

device_init(sensor);

Thanks for your help!

RE: I2C functions don’t work, but using the I2C shell does

Edvin — Thu, 03 Apr 2025 07:31:09 GMT

So you didn't get it working with the sample that I sent?

What analyzer did you use? Does it power the chip? Or is it only the thin cables shown in the picture (purple and orange) for SDA and SCL?

So it doesn't work when you have the RTT log connected but the analyzer disconnected?

What comes to mind is that perhaps your analyzer adds some pull configuration. Do you have the pull-up configuration on i2c1_default?

	i2c1_default: i2c1_default {
		group1 {
			psels = <NRF_PSEL(TWIM_SDA, 0, 2)>,
							<NRF_PSEL(TWIM_SCL, 0, 24)>;
							bias-pull-up;
		};
	};
	
	i2c1_sleep: i2c1_sleep {
		group1 {
			psels = <NRF_PSEL(TWIM_SDA, 0, 2)>,
							<NRF_PSEL(TWIM_SCL, 0, 24)>;
							low-power-enable;
		};
	};

RE: I2C functions don’t work, but using the I2C shell does

j_a536 — Wed, 02 Apr 2025 19:40:02 GMT

Thanks for your help.

Finally, it was necessary to connect to the I2C lines to observe what was really happening (it seemed impossible). I was greatly surprised when I tried using the official sensor driver again (just as I had initially attempted) and saw that it worked perfectly fine. I confirmed this both with the logic analyzer and through the RTT logs.

However, when disconnecting the analyzer (from the computer, i.e., its power supply, not the probes from the I2C lines), the microcontroller was once again unable to communicate with the sensor. Yet, it still worked when testing communication from the I2C shell.

This brings me back to my initial question. It seems clear that there is a hardware issue (which I did not design and cannot modify), but the communication works with the shell and not with the sensor driver. So, I don’t understand this inconsistency.

RE: I2C functions don’t work, but using the I2C shell does

Edvin — Tue, 25 Mar 2025 11:29:53 GMT

By the way, that solution is not optimal. I ended up with two devicetree instances in your tilt.c, because one was used to fetch the device i2c address, while the other was used to initialize it. I recommend that you check out the devAcademy course: NCS Fundamentals, which has a lesson on I2C in NCS:

Lesson 6 covers I2C:
https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/lessons/lesson-6-serial-com-i2c/topic/exercise-1-6-2/

Best regards,

Edvin

RE: I2C functions don’t work, but using the I2C shell does

Edvin — Tue, 25 Mar 2025 11:09:17 GMT

devzone.nordicsemi.com/.../AccSensor_5F00_suggestion.zip

Hello,

Sorry for the late reply. I got something working on my end, but it was with a different sensor, so you need to modify it a bit. I made it just read the "WHO_AM_I" register, which on the mpu6050 is the 0x75 register address. I also added an .overlay file in your application folder, where I did some modifications. This will overwrite whatever is in the board files, so go through them and see if you want to revert something. For instance, I changed the LEDs to match the LED pins on the nRF52832 DK.

I also changed the I2C pins in the overlay file, so you can change it back from 24 to 5. I tested it now (after I zipped it), and it still works.

Best regards,

Edvin

RE: I2C functions don’t work, but using the I2C shell does

j_a536 — Wed, 19 Mar 2025 19:25:09 GMT

I'm using NCS version 2.8.0, with a custom board based on the nRF52832 (included in the boards directory) as the target, and incorporating the sensor and other modifications according to the schematic.

RE: I2C functions don’t work, but using the I2C shell does

Edvin — Wed, 19 Mar 2025 11:49:26 GMT

What NCS version are you using, and what is your build command? Particularly, what board are you building for?

Best regards,

Edvin

RE: I2C functions don’t work, but using the I2C shell does

j_a536 — Tue, 18 Mar 2025 14:07:33 GMT

Thank you for your help! I’ve attached the zip file. I also forgot to mention that I’m unable to probe the lines due to their small size and the lack of test points :(

devzone.nordicsemi.com/.../AccSensor_5F00_simplified.zip

RE: I2C functions don’t work, but using the I2C shell does

Edvin — Tue, 18 Mar 2025 07:12:39 GMT

Hello,

Is it possible to zip and upload the application that you are testing on? I don't have that exact sensor, but I have some I2C things that I can test on with minor modifications.

Best regards,

Edvin