Running the LSM6DLS (IMU) zephyr example with nrf52840 based Xiao BLE Sense

Hi all,

I've been trying to get the samples/sensor/lsm6dsl example working with the nrf52840-based Xiao BLE Sense and have had no luck.

I guess that it's due to the power line for the sensor being connected to the P1.08

I dug into the xiao_ble_sense.dts and I can indeed see:

	lsm6ds3tr-c-en {
		compatible = "regulator-fixed-sync", "regulator-fixed";
		enable-gpios = <&gpio1 8 (NRF_GPIO_DRIVE_S0H1 | GPIO_ACTIVE_HIGH)>;
		regulator-name = "LSM6DS3TR_C_EN";
		startup-delay-us = <3000>;

However no matter how I try and drive it from the code the sensor refuses to initialize with the console output:

[00:00:00.794,647] <dbg> LSM6DSL: lsm6dsl_init_chip: failed to reboot device
[00:00:00.794,677] <err> LSM6DSL: Failed to initialize chip
*** Booting nRF Connect SDK d96769faceca ***
Begin init of lsm6ds3tr and regulator 
sensor: device not ready.

My code to run is based of the sample code for the sensor with the lsm6ds3tr_c_en modifications:

 * Copyright (c) 2018 STMicroelectronics
 * SPDX-License-Identifier: Apache-2.0

#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <zephyr/drivers/sensor.h>
#include <stdio.h>
#include <zephyr/sys/util.h>
#include <zephyr/drivers/gpio.h>
#include <zephyr/drivers/regulator.h>

static const struct device *lsm6ds3tr_c_en;

static inline float out_ev(struct sensor_value *val)
	return (val->val1 + (float)val->val2 / 1000000);

static int print_samples;
static int lsm6dsl_trig_cnt;

static struct sensor_value accel_x_out, accel_y_out, accel_z_out;
static struct sensor_value gyro_x_out, gyro_y_out, gyro_z_out;
static struct sensor_value magn_x_out, magn_y_out, magn_z_out;
#if defined(CONFIG_LSM6DSL_EXT0_LPS22HB)
static struct sensor_value press_out, temp_out;

static void lsm6dsl_trigger_handler(const struct device *dev,
				    const struct sensor_trigger *trig)
	static struct sensor_value accel_x, accel_y, accel_z;
	static struct sensor_value gyro_x, gyro_y, gyro_z;
	static struct sensor_value magn_x, magn_y, magn_z;
#if defined(CONFIG_LSM6DSL_EXT0_LPS22HB)
	static struct sensor_value press, temp;

	sensor_sample_fetch_chan(dev, SENSOR_CHAN_ACCEL_XYZ);
	sensor_channel_get(dev, SENSOR_CHAN_ACCEL_X, &accel_x);
	sensor_channel_get(dev, SENSOR_CHAN_ACCEL_Y, &accel_y);
	sensor_channel_get(dev, SENSOR_CHAN_ACCEL_Z, &accel_z);

	/* lsm6dsl gyro */
	sensor_sample_fetch_chan(dev, SENSOR_CHAN_GYRO_XYZ);
	sensor_channel_get(dev, SENSOR_CHAN_GYRO_X, &gyro_x);
	sensor_channel_get(dev, SENSOR_CHAN_GYRO_Y, &gyro_y);
	sensor_channel_get(dev, SENSOR_CHAN_GYRO_Z, &gyro_z);

	/* lsm6dsl external magn */
	sensor_sample_fetch_chan(dev, SENSOR_CHAN_MAGN_XYZ);
	sensor_channel_get(dev, SENSOR_CHAN_MAGN_X, &magn_x);
	sensor_channel_get(dev, SENSOR_CHAN_MAGN_Y, &magn_y);
	sensor_channel_get(dev, SENSOR_CHAN_MAGN_Z, &magn_z);

#if defined(CONFIG_LSM6DSL_EXT0_LPS22HB)
	/* lsm6dsl external press/temp */
	sensor_sample_fetch_chan(dev, SENSOR_CHAN_PRESS);
	sensor_channel_get(dev, SENSOR_CHAN_PRESS, &press);

	sensor_sample_fetch_chan(dev, SENSOR_CHAN_AMBIENT_TEMP);
	sensor_channel_get(dev, SENSOR_CHAN_AMBIENT_TEMP, &temp);

	if (print_samples) {
		print_samples = 0;

		accel_x_out = accel_x;
		accel_y_out = accel_y;
		accel_z_out = accel_z;

		gyro_x_out = gyro_x;
		gyro_y_out = gyro_y;
		gyro_z_out = gyro_z;

		magn_x_out = magn_x;
		magn_y_out = magn_y;
		magn_z_out = magn_z;

#if defined(CONFIG_LSM6DSL_EXT0_LPS22HB)
		press_out = press;
		temp_out = temp;


int main(void)
	int cnt = 0;
	char out_str[64];
	struct sensor_value odr_attr;
    const struct device *const lsm6dsl_dev = DEVICE_DT_GET_ONE(st_lsm6dsl);

	printk("Begin init of lsm6ds3tr and regulator \n");
    /* Initialize the regulator device */
	lsm6ds3tr_c_en = DEVICE_DT_GET(DT_PATH(lsm6ds3tr_c_en));
    if (!device_is_ready(lsm6ds3tr_c_en)) {
        printk("Regulator device not ready\n");
        return 0;

    /* Enable the regulator */
    if (regulator_enable(lsm6ds3tr_c_en) < 0) {
        printk("Failed to enable regulator\n");
        return 0;


	if (!device_is_ready(lsm6dsl_dev)) {
		printk("sensor: device not ready.\n");
		return 0;

	/* set accel/gyro sampling frequency to 104 Hz */
	odr_attr.val1 = 104;
	odr_attr.val2 = 0;

	if (sensor_attr_set(lsm6dsl_dev, SENSOR_CHAN_ACCEL_XYZ,
			    SENSOR_ATTR_SAMPLING_FREQUENCY, &odr_attr) < 0) {
		printk("Cannot set sampling frequency for accelerometer.\n");
		return 0;

	if (sensor_attr_set(lsm6dsl_dev, SENSOR_CHAN_GYRO_XYZ,
			    SENSOR_ATTR_SAMPLING_FREQUENCY, &odr_attr) < 0) {
		printk("Cannot set sampling frequency for gyro.\n");
		return 0;

	struct sensor_trigger trig;


	if (sensor_trigger_set(lsm6dsl_dev, &trig, lsm6dsl_trigger_handler) != 0) {
		printk("Could not set sensor type and channel\n");
		return 0;

	if (sensor_sample_fetch(lsm6dsl_dev) < 0) {
		printk("Sensor sample update error\n");
		return 0;

	while (1) {
		/* Erase previous */
		printf("LSM6DSL sensor samples:\n\n");

		/* lsm6dsl accel */
		sprintf(out_str, "accel x:%f ms/2 y:%f ms/2 z:%f ms/2",
		printk("%s\n", out_str);

		/* lsm6dsl gyro */
		sprintf(out_str, "gyro x:%f dps y:%f dps z:%f dps",
		printk("%s\n", out_str);

		/* lsm6dsl external magn */
		sprintf(out_str, "magn x:%f gauss y:%f gauss z:%f gauss",
		printk("%s\n", out_str);

#if defined(CONFIG_LSM6DSL_EXT0_LPS22HB)
		/* lsm6dsl external press/temp */
		sprintf(out_str, "press: %f kPa - temp: %f deg",
			out_ev(&press_out), out_ev(&temp_out));
		printk("%s\n", out_str);

		printk("loop:%d trig_cnt:%d\n\n", ++cnt, lsm6dsl_trig_cnt);

		print_samples = 1;

And my prj.conf:



I am trying to drive this the proper way but am I missing something obvious?

Should I just ignore the config and drive P1.08 manually?

Thanks for taking a look!
I'm using nRF Connect SDK v2.6.0 (latest available at the time of posting)

  • Hi  ,

    Thanks and yes I have those changes already as I'm running ncs 2.6.0. You can see the changes in the xiao_ble_sense.dts that I posted previously. Namely the:

    		enable-gpios = <&gpio1 8 (NRF_GPIO_DRIVE_S0H1 | GPIO_ACTIVE_HIGH)>;
    		startup-delay-us = <3000>;
    I can also see in that issue that the problem wasn't resolved for some. Trying to get to the bottom of it but no luck.

  • Hi mentarus,

    Sorry I didn't notice that.

    This is tricky because we don't have a Xiao BLE Sense module here to debug what could be wrong.

    I was going to suggest trying to drive the sensor with another source to be sure that the power line is the problem here, but an internet search shows me that the Xiao BLE Sense module is a closed package, and that is not possible..

    The commit message where the startup-delay-us was updated to 3000 simply says that the value seems to work. Without debugging, I could only suggest you increase it further. Could you maybe try this?

    Do you think the people on the Seeed's forums might have an idea?

    Sorry, I realize I am not being very helpful here Disappointed

  • Thanks I tried taking it up to 10,000 and still nothing.

    I'm currently going through the Arduino library which seems to work fine unlike Zephyr to figure out what it is doing differently.

    Depending on where you are I can order a board for you of Amazon very quickly. If that works for you, just DM me.

Reply Children
  • What are the I2C pull-up resistors connected to? The voltage of that source must be 0V prior to raising P1.08 to power up the sensor; typically that requires using P1.08 as the pull-up resistor connection power source, although a second io pin could be used provided it is raised to 3volts-ish after P1.08. Why? I2C pins will phantom power or back-drive the sensor and mess up the internal power-up sequencing. A common mistake is to connect pull-ups to nRF VDD which causes problems; if using internal nRF52840 io pull-ups on SDA and SCL then these must be disabled prior to driving P1.08 high to power up the sensor.

    Edit: Found a schematic, looks ok assuming 6D_PWR drives both VDD and I2C pull-ups