Index

* Introduction
* Integration details
* More information
* Copyright

Introduction

This repository contains Linux kernel v3.18 with STMicroelectronics MEMS sensor support. STM sensor drivers are located under the directory drivers/iio organized by sensor type:

Inertial Module Unit (IMU):

LSM6DS3, LSM6DS3H, LSM6DSL, LSM6DSM, LSM9DS0, LSM9DS1, ISM330DLC, LSM6DSO, ASM330LHH, LSM6DSR

Accelerometer:

LIS2DH, LIS2DH12, LIS3DH, LIS2DG, LSM303AH, LIS2DS12, LIS2HH12, LIS2DW12, LIS3LV02DL, LSM303DLH, LSM303DLHC, LSM330D, LSM330DL, LSM330DLC, LIS331DL, LIS331DLH, LSM303DL, LSM303DLM, LSM330, LSM303AGR, LIS3DHH, IIS2DH, ISM303DAC, IIS3DHHC

Gyroscope:

L3G4200D, LSM330D, LSM330DL, L3GD20, L3GD20H, L3G4IS, LSM330, LSM330DLC

Magnetometer:

LIS3MDL, LSM9DS1, LSM303AH, LSM303AGR, LSM303DLH, LSM303DLHC, LSM303DLM, LIS2MDL, IIS2MDC, ISM303DAC

Humidity:

HTS221

Pressure:

LPS22HB, LPS22HD, LPS25H, LPS331AP, LPS001WP, LPS33HW, LPS35HW, LPS22HH

Data collected by STM sensors are pushed to userland through the kernel buffers of Linux IIO framework. User space applications can get sensor events by reading the related IIO devices created in the /dev directory (/dev/iio{x}). Please see IIO for more information.

All STM MEMS sensors support I2C/SPI digital interface. Please refer to I2C and SPI for detailed documentation.

Integration details

In order to explain how to integrate STM sensors in a different kernel, please consider the following LSM6DSM IMU example

Source code integration

• Copy driver source code into the target directory (e.g. drivers/iio/imu)
• Edit related Kconfig (e.g. drivers/iio/imu/Kconfig) to include LSM6DSM support:

    source "drivers/iio/imu/st_lsm6dsm/Kconfig"

• Edit related Makefile (e.g. drivers/iio/imu/Makefile) adding the following line:

    obj-y += lsm6dsm/

• Add custom events into include/uapi/linux/iio/types.h (follow a sample patch for kernel 3.18):

    @@ -68,6 +76,7 @@ enum iio_event_type {
            IIO_EV_TYPE_ROC,
            IIO_EV_TYPE_THRESH_ADAPTIVE,
            IIO_EV_TYPE_MAG_ADAPTIVE,
    +       IIO_EV_TYPE_FIFO_FLUSH,
    };

    @@ -81,6 +90,8 @@ enum iio_event_direction {
            IIO_EV_DIR_EITHER,
            IIO_EV_DIR_RISING,
            IIO_EV_DIR_FALLING,
    +       IIO_EV_DIR_FIFO_EMPTY,
    +       IIO_EV_DIR_FIFO_DATA,
    };

• Add custom channel types include/uapi/linux/iio/types.h depending on the custom sensor implemented into driver (follow a sample patch for kernel 3.18):

    @@ -30,6 +30,14 @@ enum iio_chan_type {
            IIO_CCT,
            IIO_PRESSURE,
            IIO_HUMIDITYRELATIVE,
    +       IIO_SIGN_MOTION,
    +       IIO_STEP_DETECTOR,
    +       IIO_STEP_COUNTER,
    +       IIO_TILT,
    +       IIO_TAP,
    +       IIO_TAP_TAP,
    +       IIO_WRIST_TILT_GESTURE,
    +       IIO_GESTURE,
    };

Device Tree configuration

To enable driver probing, add the lsm6dsm node to the platform device tree as described below.

Required properties:

- compatible: "st,lsm6dsm"

- reg: the I2C address or SPI chip select the device will respond to

- interrupt-parent: phandle to the parent interrupt controller as documented in interrupts

- interrupts: interrupt mapping for IRQ as documented in interrupts

Recommended properties for SPI bus usage:

- spi-max-frequency: maximum SPI bus frequency as documented in SPI

Optional properties:

- st,drdy-int-pin: MEMS sensor interrupt line to use (default 1)

Device Tree Integration Examples

I2C example (based on Raspberry PI 3):

  &i2c0 {
  	status = "ok";
  	#address-cells = <0x1>;
  	#size-cells = <0x0>;
  	lsm6dsm@6b {
  		compatible = "st,lsm6dsm";
  		reg = <0x6b>;
  		interrupt-parent = <&gpio>;
  		interrupts = <26 IRQ_TYPE_LEVEL_HIGH>;
  };

SPI example (based on Raspberry PI 3):

  &spi0 {
  	status = "ok";
  	#address-cells = <0x1>;
  	#size-cells = <0x0>;
  	lsm6dsm@0 {
  		spi-max-frequency = <500000>;
  		compatible = "st,lsm6dsm";
  		reg = <0>;
  		interrupt-parent = <&gpio>;
  		interrupts = <26 IRQ_TYPE_LEVEL_HIGH>;
  	};

Kernel configuration

Configure kernel with make menuconfig (alternatively use make xconfig or make qconfig)

  Device Drivers  --->
  	<M> Industrial I/O support  --->
  		Inertial measurement units  --->
  		<M>   STMicroelectronics LSM6DSM/LSM6DSL sensor  --->

More Information

http://st.com

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/iio

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/i2c

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/spi

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bings/interrupt-controller/interrupts.txt

Copyright

Copyright (C) 2019 STMicroelectronics

This software is distributed under the GNU General Public License - see the accompanying COPYING file for more details.