IKS01A2 MEMS expansion board

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1. Article purpose[edit source]

The purpose of this article is to explain how to integrate the IKS01A2 expansion board with STM32MP157C-DK2, managed by Linux on Cortex^®-A7.

The IKS01A2 board is an expansion board that includes several motion MEMS like HTS221 and LSM6DSL.

This article provides step-by-step instructions to:

configure Linux software to support IKS01A2 expansion board,
activate/use several motion MEMS such as HTS221 and LSM6DSL.

2. Prerequisites[edit source]

2.1. Hardware prerequisites[edit source]

STM32MP157C-DK2

STM32MP157C-DK2

For more information about the STM32 discovery board and how to start it up, jump to this section Getting_started/STM32MP1_boards/STM32MP157x-DK2

IKS01A2 expansion board

IKS01A2 expansion board

2.2. Software prerequisites[edit source]

The STM32MP157C-DK2 board must be downloaded with appropriate software in order to support IKS01A2 expansion board. For proceeding, follow the step-by-step instructions provided at STM32MP157C-DK2 Let's start.

3. Software customization to support IKS01A2 expansion board[edit source]

The STM32MP157C-DK2 Linux software must be configured to activate the IKS01A2 board connected on top of the STM32MP157C-DK2 board.

The configuration consists in modifying the STM32MP157C-DK2 Linux kernel and managing some new device tree elements.

3.1. Kernel configuration[edit source]

By default, the motion MEMS drivers present on IKS01A2 expansion board are enabled in STM32MP1 kernel configuration: hts221, pressure(lp22hb) and lsm6dsl. The device tree must be updated to declare and activate them.

To check whether associated drivers are enabled inside the kernel, type the commands provided here below :

  cat /proc/config.gz | gunzip | grep HTS221
CONFIG_HTS221=y
CONFIG_HTS221_I2C=y
CONFIG_HTS221_SPI=y

  cat /proc/config.gz | gunzip | grep ST_PRESS
CONFIG_IIO_ST_PRESS=m
CONFIG_IIO_ST_PRESS_I2C=m
CONFIG_IIO_ST_PRESS_SPI=m

  cat /proc/config.gz | gunzip |  grep ST_LSM6DS
CONFIG_IIO_ST_LSM6DSX=m
CONFIG_IIO_ST_LSM6DSX_I2C=m
CONFIG_IIO_ST_LSM6DSX_SPI=m

Information

If the above configurations are not enabled, follow the indications given in Modify, rebuild and reload the Linux® kernel

3.2. Kernel device tree configuration[edit source]

3.2.1. Hardware / software interface[edit source]

The HTS221 and LSM6DSL motion MEMS present on IKS01A2 expansion board are involved in the following use case.
According to IKS01A2 user manual^[1], both motion MEMS are controlled by I²C bus.

In the schematics of IKS01A2 ^[2] and STM32MP157C-DK2^[3] presented below, the pins that are interconnected are highlighted.

IKS01A2 schematic (Arduino connector) ^[2]
- Pins 10 and 9 of CN5 are used for I²C Bus (SDA and SCL) (I2C1 and I2C2 bus instances are mixed via JP7 and JP8 jumpers)
- Pins 6 and 5 of CN9 are used to manage interruptions on LSM6DSL motion MEMS (indicated for information: not used on kernel configuration).

IKS01A2 schematics extract

STM32MP157C-DK2 schematic (Arduino connector) ^[3]
- Pins 10 and 9 of CN5 are used for I²C Bus (I2C5_SDA and I2C5_SCL)
- Pins 6 and 5 of CN14 are used to manage interruptions on LSM6DSL motion MEMS (indicated for information: not used on kernel configuration)

stm32mp157c-dk2 schematics extract

Warning

I2C5 bus instance MUST be enabled by software in order to access the motion MEMS present on IKS01A2

3.2.2. Kernel device tree configuration[edit source]

As indicated in previous section, the IKS01A2 expansion board is controlled via I²C bus. On STM32MP157C-DK2, the associated I²C bus is I2C5.

The I2C5 bus must be activated into STM32MP157C-DK2 device tree and a node must be added for each hardware to be supported (see entries like hts221, as shown in the device tree content example below).

For that, add following content into stm32mp157c-dk2.dts file:

 &i2c5 {
	status = "okay";

	hts221@5f {
		compatible = "st,hts221";
		reg = <0x5f>;
	};
	lsm6dsl@6b {
		compatible = "st,lsm6dsl";
		reg = <0x6b>;
	};
 };

Information

To generate a new device tree, please follow the indications given in Modify, rebuild and reload the Linux® kernel

3.3. Activate the new configuration in the STM32MP157C-DK2 board[edit source]

Prerequisites: The device tree and the Linux kernel must have been regenerated. If not done yet, follow the indications given in Modify, rebuild and reload the Linux® kernel

Add the two generated files in the board file system, precisely in the bootfs partition (/boot directory)

 ls -1 /boot/stm32*dk2*
                                                                                              
/boot/stm32mp157c-dk2-a7-examples.dtb
/boot/stm32mp157c-dk2-iks01a2.dtb
/boot/stm32mp157c-dk2-m4-examples.dtb
/boot/stm32mp157c-dk2.dtb

Add a new entry in stm32mp157c-dk2_extlinux.conf file located in /boot/mmc0_extlinux/. If the mmc0_<something> directory is not available, add the new entry in /boot/mmc0_extlinux/extlinux.conf.

 # Generic Distro Configuration file generated by OpenEmbedded
 menu title Select the boot mode
 MENU BACKGROUND ../splash.bmp
 TIMEOUT 20
 DEFAULT stm32mp157c-dk2-iks01a2
 LABEL OpenSTLinux
        KERNEL /uImage
        FDTDIR /
        INITRD /uInitrd
        APPEND root=PARTUUID=e91c4e10-16e6-4c0e-bd0e-77becf4a3582 rootwait rw console=ttySTM0,115200
LABEL stm32mp157c-dk2-a7-examples
        KERNEL /uImage
        FDT /stm32mp157c-dk2-a7-examples.dtb
        INITRD /uInitrd
        APPEND root=PARTUUID=e91c4e10-16e6-4c0e-bd0e-77becf4a3582 rootwait rw console=ttySTM0,115200
LABEL stm32mp157c-dk2-m4-examples
        KERNEL /uImage
        FDT /stm32mp157c-dk2-m4-examples.dtb
        INITRD /uInitrd
        APPEND root=PARTUUID=e91c4e10-16e6-4c0e-bd0e-77becf4a3582 rootwait rw console=ttySTM0,115200
 LABEL stm32mp157c-dk2-iks01a2
        KERNEL /uImage
        FDT /stm32mp157c-dk2-iks01a2.dtb
        APPEND root=PARTUUID=e91c4e10-16e6-4c0e-bd0e-77becf4a3582 rootwait rw console=ttySTM0,115200

Warning

Do not forget to synchronize the file system before rebooting the board
sync

Reboot the board

3.4. Verify the new configuration on board[edit source]

Verify if i2c5 is enabled:

  cat /proc/device-tree/soc/i2c\@40015000/status 
okay

Verify if the motion MEMS drivers are declared in the device tree node:

 ls -l /proc/device-tree/soc/i2c\@40015000/

total 0
-r--r--r-- 1 root root  4 Feb  7 15:56 #address-cells
-r--r--r-- 1 root root  4 Feb  7 15:56 #size-cells
-r--r--r-- 1 root root  4 Feb  7 15:56 clock-frequency
-r--r--r-- 1 root root  8 Feb  7 15:56 clocks
-r--r--r-- 1 root root 17 Feb  7 15:56 compatible
drwxr-xr-x 2 root root  0 Feb  7 15:51 hts221@5f
-r--r--r-- 1 root root  4 Feb  7 15:56 i2c-scl-falling-time-ns
-r--r--r-- 1 root root  4 Feb  7 15:56 i2c-scl-rising-time-ns
-r--r--r-- 1 root root 12 Feb  7 15:56 interrupt-names
-r--r--r-- 1 root root 28 Feb  7 15:56 interrupts-extended
drwxr-xr-x 2 root root  0 Feb  7 15:51 lsm6dsl@6b
-r--r--r-- 1 root root  4 Feb  7 15:56 name
-r--r--r-- 1 root root  4 Feb  7 15:56 pinctrl-0
-r--r--r-- 1 root root  4 Feb  7 15:56 pinctrl-1
-r--r--r-- 1 root root 14 Feb  7 15:56 pinctrl-names
-r--r--r-- 1 root root  4 Feb  7 15:56 power-domains
-r--r--r-- 1 root root  8 Feb  7 15:56 reg
-r--r--r-- 1 root root  8 Feb  7 15:56 resets
-r--r--r-- 1 root root 12 Feb  7 15:56 st,syscfg-fmp
-r--r--r-- 1 root root  5 Feb  7 15:56 status
-r--r--r-- 1 root root  0 Feb  7 15:56 wakeup-source

Verify if the motion MEMS drivers are correctly probed and if the system provides access to the associated hardware:

  grep OF_NAME /sys/bus/iio/devices/iio\:device*/uevent
/sys/bus/iio/devices/iio:device0/uevent:OF_NAME=hts221
/sys/bus/iio/devices/iio:device1/uevent:OF_NAME=lsm6dsl
/sys/bus/iio/devices/iio:device2/uevent:OF_NAME=lsm6dsl

Information

If the results are different, check that

the expansion board is correctly connected
all steps, described above, were correctly done.

4. Read motion MEMS via bash script[edit source]

The goal of this section is to read the informations provided by the Linux kernel interface and to process it with a bash script.

4.1. List of sensor entries[edit source]

The IKS01A2 expansion board provides several MEMS like HTS221, LSM6DSL, LPS22HB.
The list of hardware MEMS detected by Linux via the IIO framework can be verified in the sysfs.

 grep OF_NAME /sys/bus/iio/devices/iio\:device*/uevent
/sys/bus/iio/devices/iio:device0/uevent:OF_NAME=hts221
/sys/bus/iio/devices/iio:device1/uevent:OF_NAME=lsm6dsl
/sys/bus/iio/devices/iio:device2/uevent:OF_NAME=lsm6dsl

This list provides the association between entries and MEMS drivers. In the rest of the article, this list is used a as reference.

4.2. HTS221: Temperature/Humidity[edit source]

The HTS221 is a capacitive digital sensor for relative humidity and temperature.

In this example, hts221 entry is /sys/bus/iio/devices/iio:device0/. In case the user has a different setup, the entry should be adapted accordingly in the scripts provided hereafter.

4.2.1. Temperature[edit source]

Read IIO entries associated to the temperature for HTS221 driver

  cat /sys/bus/iio/devices/iio\:device0/in_temp_raw
  cat /sys/bus/iio/devices/iio\:device0/in_temp_offset
  cat /sys/bus/iio/devices/iio\:device0/in_temp_scale

Calculate real temperature according with the following formula

Temperature = ( Raw value + Offset value) * Scale value)

Calculate temperature by shell script : static IIO entries

Content of hts221_read_temperature_on_device0.sh:

#!/bin/sh
raw=`cat /sys/bus/iio/devices/iio\:device0/in_temp_raw`
offset=`cat /sys/bus/iio/devices/iio\:device0/in_temp_offset`
scale=`cat /sys/bus/iio/devices/iio\:device0/in_temp_scale`
printf "Value read: raw         %0f\n" $raw
printf "Value read: offset      %0f\n" $offset
printf "Value read: scale       %0f\n" $scale

temperature=`echo "scale=2;$raw*$scale + $offset*$scale" | bc`

echo "Temperature $temperature"
printf "Temperature %.01f\n" $temperature

Calculate temperature by shell script: auto detection of IIO entries

Content of hts221_read_temperature_with_entry_detection.sh:

#!/bin/sh
DRIVER_NAME=hts221
for d in `ls -d1 /sys/bus/iio/devices/*device*`;
do
    if grep -q $DRIVER_NAME $d/name ;
    then
        raw=`cat $d/in_temp_raw`
        offset=`cat $d/in_temp_offset`
        scale=`cat $d/in_temp_scale`

        printf "Value read: raw         %0f\n" $raw
        printf "Value read: offset      %0f\n" $offset
        printf "Value read: scale       %0f\n" $scale

        temperature=`echo "scale=2;$raw*$scale + $offset*$scale" | bc`

        echo "Temperature $temperature"
        printf "Temperature %.01f\n" $temperature

        break;
    fi
done

Test on board

  ./hts221_read_temperature_on_device0.sh
Value read: raw         563.000000
Value read: offset      1036.674817
Value read: scale       0.019172
Temperature 30.668765624
Temperature 30.7

4.2.2. Humidity[edit source]

Read IIO entries associated to humidity for HTS221 driver

 cat /sys/bus/iio/devices/iio\:device0/in_humidityrelative_raw
 cat /sys/bus/iio/devices/iio\:device0/in_humidityrelative_offset
 cat /sys/bus/iio/devices/iio\:device0/in_humidityrelative_scale

Calculate real humidity according with the following formula

Humidity = ( Raw value + Offset value) * Scale value)

Calculate humidity by shell script: static IIO entries

Content of hts221_read_humidity_on_device0.sh:

#!/bin/sh
raw=`cat /sys/bus/iio/devices/iio\:device0/in_humidityrelative_raw`
offset=`cat /sys/bus/iio/devices/iio\:device0/in_humidityrelative_offset`
scale=`cat /sys/bus/iio/devices/iio\:device0/in_humidityrelative_scale`
printf "Value read: raw         %0f\n" $raw
printf "Value read: offset      %0f\n" $offset
printf "Value read: scale       %0f\n" $scale

humidity=`echo "scale=2;$raw*$scale + $offset*$scale" | bc`

echo "Humidity $humidity"
printf "Humidity %.01f\n" $humidity

Calculate humidity by shell script: auto detection of IIO entries

Content of hts221_read_humidity_with_entry_detection.sh:

#!/bin/sh
DRIVER_NAME=hts221
for d in `ls -d1 /sys/bus/iio/devices/*device*`;
do
    if grep -q $DRIVER_NAME $d/name ;
    then
        raw=`cat $d/in_humidityrelative_raw`
        offset=`cat $d/in_humidityrelative_offset`
        scale=`cat $d/in_humidityrelative_scale`

        printf "Value read: raw         %0f\n" $raw
        printf "Value read: offset      %0f\n" $offset
        printf "Value read: scale       %0f\n" $scale

        humidity=`echo "scale=2;$raw*$scale + $offset*$scale" | bc`

        echo "Humidity $humidity"
        printf "Humidity %.01f\n" $humidity

        break;
    fi
done

Test on board

 ./hts221_read_humidity_on_device0.sh
Value read: raw         2669.000000
Value read: offset      -10661.500000
Value read: scale       -0.003000
Humidity 23.977500000
Humidity 24.0

4.3. LSM6DSL: accelerometer/gyroscope[edit source]

The LSM6DSL is an inertial measurement unit (IMU) with ultra-low power and high accuracy, for smartphones and battery operated IoT, gaming, wearables and consumer electronics.

In this example, lsm6dsl entries are /sys/bus/iio/devices/iio:device1/ and /sys/bus/iio/devices/iio:device2/.
The device2 entry is dedicated to accelerometer and the device1 one to gyroscope.

4.3.1. Accelerometer[edit source]

Read IIO entries associated to accelerometer for LSM6DSL driver

 cat /sys/bus/iio/devices/iio\:device2/in_accel_scale
 cat /sys/bus/iio/devices/iio\:device2/in_accel_x_raw
 cat /sys/bus/iio/devices/iio\:device2/in_accel_y_raw
 cat /sys/bus/iio/devices/iio\:device2/in_accel_z_raw

Calculate accelerometer values according with the following formula

X = Raw value * scale value * (256.0 / 9.81)
Y = Raw value * scale value * (256.0 / 9.81)
Z = Raw value * scale value * (256.0 / 9.81)

Calculate accelerometer value by shell script: static IIO entries

Content of lsm6dsl_accel_read_on_device2.sh:

#!/bin/sh
rscale=`cat /sys/bus/iio/devices/iio\:device2/in_accel_scale`
xraw=`cat /sys/bus/iio/devices/iio\:device2/in_accel_x_raw`
yraw=`cat /sys/bus/iio/devices/iio\:device2/in_accel_y_raw`
zraw=`cat /sys/bus/iio/devices/iio\:device2/in_accel_z_raw`

printf "Value read: X (raw/scale)  %d / %.06f \n" $xraw $rscale
printf "Value read: Y (raw/scale)  %d / %.06f \n" $yraw $rscale
printf "Value read: Z (raw/scale)  %d / %.06f \n" $zraw $rscale

factor=`echo "scale=2;256.0 / 9.81" | bc`
xval=`echo "scale=2;$xraw*$rscale*$factor" | bc`
yval=`echo "scale=2;$yraw*$rscale*$factor" | bc`
zval=`echo "scale=2;$zraw*$rscale*$factor" | bc`

printf "Accelerometer value: [ %.02f, %.02f, %.02f ]\n" $xval $yval $zval

Calculate accelerometer value by shell script: auto detection of IIO entries

Content of lsm6dsl_accel_read_with_entry_detection.sh:

#!/bin/sh
DRIVER_NAME=lsm6dsl_accel       
for d in `ls -d1 /sys/bus/iio/devices/*device*`;
do
    if grep -q $DRIVER_NAME $d/name ;
    then
        rscale=`cat $d/in_accel_x_scale`
        xraw=`cat $d/in_accel_x_raw`
        yraw=`cat $d/in_accel_y_raw`
        zraw=`cat $d/in_accel_z_raw`

        printf "Value read: X (raw/scale)  %d / %.06f \n" $xraw $rscale
        printf "Value read: Y (raw/scale)  %d / %.06f \n" $yraw $rscale
        printf "Value read: Z (raw/scale)  %d / %.06f \n" $zraw $rscale

        factor=`echo "scale=2;256.0 / 9.81" | bc`
        xval=`echo "scale=2;$xraw*$rscale*$factor" | bc`
        yval=`echo "scale=2;$yraw*$rscale*$factor" | bc`
        zval=`echo "scale=2;$zraw*$rscale*$factor" | bc`

        printf "Accelerometer value: [ %.02f, %.02f, %.02f ]\n" $xval $yval $zval
 
        break;
    fi
done

Test on board

 ./lsm6dsl_accel_read_on_device2.sh
Value read: X (raw/scale)  104 / 0.000598 
Value read: Y (raw/scale)  -16378 / 0.000598 
Value read: Z (raw/scale)  -1117 / 0.000598 
Accelerometer value: [ 1.62, -255.53, -17.43 ]

4.3.2. Gyroscope[edit source]

Read IIO entries associated to gyroscope for LSM6DSL driver

 cat /sys/bus/iio/devices/iio\:device1/in_anglvel_scale
 cat /sys/bus/iio/devices/iio\:device1/in_anglvel_x_raw
 cat /sys/bus/iio/devices/iio\:device1/in_anglvel_y_raw
 cat /sys/bus/iio/devices/iio\:device1/in_anglvel_z_raw

Calculate gyroscope values according following formula

X = Raw value * scale value * (256.0 / 9.81)
Y = Raw value * scale value * (256.0 / 9.81)
Z = Raw value * scale value * (256.0 / 9.81)

Calculate gyroscope value by shell script: static IIO entries

Content of lsm6dsl_gyro_read_on_device1.sh:

#!/bin/sh
rscale=`cat /sys/bus/iio/devices/iio\:device1/in_anglvel_scale`
xraw=`cat /sys/bus/iio/devices/iio\:device1/in_anglvel_x_raw`
yraw=`cat /sys/bus/iio/devices/iio\:device1/in_anglvel_y_raw`
zraw=`cat /sys/bus/iio/devices/iio\:device1/in_anglvel_z_raw`

printf "Value read: X (raw/scale)  %d / %.06f \n" $xraw $rscale
printf "Value read: Y (raw/scale)  %d / %.06f \n" $yraw $rscale
printf "Value read: Z (raw/scale)  %d / %.06f \n" $zraw $rscale

factor=`echo "scale=2;256.0 / 9.81" | bc`
xval=`echo "scale=2;$xraw*$rscale*$factor" | bc`
yval=`echo "scale=2;$yraw*$rscale*$factor" | bc`
zval=`echo "scale=2;$zraw*$rscale*$factor" | bc`

printf "Gyroscope value: [ %.02f, %.02f, %.02f ]\n" $xval $yval $zval

Calculate gyroscope value by shell script: auto detection of IIO entries

Content of lsm6dsl_gyro_read_with_entry_detection.sh:

#!/bin/sh
DRIVER_NAME=lsm6dsl_gyro       
for d in `ls -d1 /sys/bus/iio/devices/*device*`;
do
    if grep -q $DRIVER_NAME $d/name ;
    then
        rscale=`cat $d/in_anglvel_scale`
        xraw=`cat $d/in_anglvel_x_raw`
        yraw=`cat $d/in_anglvel_y_raw`
        zraw=`cat $d/in_anglvel_z_raw`

        printf "Value read: X (raw/scale)  %d / %.06f \n" $xraw $rscale
        printf "Value read: Y (raw/scale)  %d / %.06f \n" $yraw $rscale
        printf "Value read: Z (raw/scale)  %d / %.06f \n" $zraw $rscale

        factor=`echo "scale=2;256.0 / 9.81" | bc`
        xval=`echo "scale=2;$xraw*$rscale*$factor" | bc`
        yval=`echo "scale=2;$yraw*$rscale*$factor" | bc`
        zval=`echo "scale=2;$zraw*$rscale*$factor" | bc`

        printf "Gyroscope value: [ %.02f, %.02f, %.02f ]\n" $xval $yval $zval

        break;
    fi
done

Test on board

 ./lsm6dsl_gyro_read_on_device1.sh
Value read: X (raw/scale)  -2293 / 0.000153 
Value read: Y (raw/scale)  150 / 0.000153 
Value read: Z (raw/scale)  -111 / 0.000153 
Gyroscope value: [ -9.15, 0.60, -0.44 ]

4.4. BASH: script with all the measurements[edit source]

Content of iks01a2.sh

#!/bin/sh
echo "============================="
echo "===       HTS221          ==="
echo "===    (temperature)      ==="
echo "============================="
raw=`cat /sys/bus/iio/devices/iio\:device0/in_temp_raw`
offset=`cat /sys/bus/iio/devices/iio\:device0/in_temp_offset`
scale=`cat /sys/bus/iio/devices/iio\:device0/in_temp_scale`
printf "Value read: raw      %0f\n" $raw
printf "Value read: offset   %0f\n" $offset
printf "Value read: scale    %0f\n" $scale

temperature=`echo "scale=2;$raw*$scale + $offset*$scale" | bc`

echo "Temperature $temperature"
printf "Temperature %.02f\n" $temperature

echo "============================="
echo "===       HTS221          ==="
echo "===    (humidity)         ==="
echo "============================="
raw=`cat /sys/bus/iio/devices/iio\:device0/in_humidityrelative_raw`
offset=`cat /sys/bus/iio/devices/iio\:device0/in_humidityrelative_offset`
scale=`cat /sys/bus/iio/devices/iio\:device0/in_humidityrelative_scale`
printf "Value read: raw         %0f\n" $raw
printf "Value read: offset      %0f\n" $offset
printf "Value read: scale       %0f\n" $scale

humidity=`echo "scale=2;$raw*$scale + $offset*$scale" | bc`

echo "Humidity $humidity"
printf "Humidity %.02f\n" $humidity


echo "============================="
echo "===      LSM6DSL          ==="
echo "===    (accelerometer)    ==="
echo "============================="

rscale=`cat /sys/bus/iio/devices/iio\:device2/in_accel_scale`
xraw=`cat /sys/bus/iio/devices/iio\:device2/in_accel_x_raw`
yraw=`cat /sys/bus/iio/devices/iio\:device2/in_accel_y_raw`
zraw=`cat /sys/bus/iio/devices/iio\:device2/in_accel_z_raw`

printf "Value read: X (raw/scale)  %d / %.06f \n" $xraw $rscale
printf "Value read: Y (raw/scale)  %d / %.06f \n" $yraw $rscale
printf "Value read: Z (raw/scale)  %d / %.06f \n" $zraw $rscale

factor=`echo "scale=2;256.0 / 9.81" | bc`
xval=`echo "scale=2;$xraw*$rscale*$factor" | bc`
yval=`echo "scale=2;$yraw*$rscale*$factor" | bc`
zval=`echo "scale=2;$zraw*$rscale*$factor" | bc`

printf "Accelerometer value: [ %.02f, %.02f, %.02f ]\n" $xval $yval $zval

echo "============================="
echo "===      LSM6DSL          ==="
echo "===    (gyroscope)        ==="
echo "============================="

xscale=`cat /sys/bus/iio/devices/iio\:device1/in_anglvel_scale`
xraw=`cat /sys/bus/iio/devices/iio\:device1/in_anglvel_x_raw`
yraw=`cat /sys/bus/iio/devices/iio\:device1/in_anglvel_y_raw`
zraw=`cat /sys/bus/iio/devices/iio\:device1/in_anglvel_z_raw`

printf "Value read: X (raw/scale)  %d / %.06f \n" $xraw $rscale
printf "Value read: Y (raw/scale)  %d / %.06f \n" $yraw $rscale
printf "Value read: Z (raw/scale)  %d / %.06f \n" $zraw $rscale

factor=`echo "scale=2;256.0 / 9.81" | bc`
xval=`echo "scale=2;$xraw*$rscale*$factor" | bc`
yval=`echo "scale=2;$yraw*$rscale*$factor" | bc`
zval=`echo "scale=2;$zraw*$rscale*$factor" | bc`

printf "Gyroscope value: [ %.02f, %.02f, %.02f ]\n" $xval $yval $zval

Content of iks01a2_with_auto_detection.sh

#!/bin/sh

for d in `ls -d1 /sys/bus/iio/devices/*device*`;
do
    # for hts221: Temperature + Humidity
    if grep -q hts221 $d/name ;
    then
        echo "============================="
        echo "===       HTS221          ==="
        echo "===    (temperature)      ==="
        echo "============================="
        raw=`cat $d/in_temp_raw`
        offset=`cat $d/in_temp_offset`
        scale=`cat $d/in_temp_scale`

        printf "Value read: raw         %0f\n" $raw
        printf "Value read: offset      %0f\n" $offset
        printf "Value read: scale       %0f\n" $scale

        temperature=`echo "scale=2;$raw*$scale + $offset*$scale" | bc`

        echo "Temperature $temperature"
        printf "Temperature %.02f\n" $temperature

        echo "============================="
        echo "===       HTS221          ==="
        echo "===    (humidity)         ==="
        echo "============================="
        raw=`cat $d/in_humidityrelative_raw`
        offset=`cat $d/in_humidityrelative_offset`
        scale=`cat $d/in_humidityrelative_scale`

        printf "Value read: raw         %0f\n" $raw
        printf "Value read: offset      %0f\n" $offset
        printf "Value read: scale       %0f\n" $scale

        humidity=`echo "scale=2;$raw*$scale + $offset*$scale" | bc`

        echo "Humidity $humidity"
        printf "Humidity %.02f\n" $humidity
    fi

    # for lsm6dsl: accelerometer
    if grep -q lsm6dsl_accel $d/name ;
    then
        echo "============================="
        echo "===      LSM6DSL          ==="
        echo "===    (accelerometer)    ==="
        echo "============================="
        rscale=`cat $d/in_accel_scale`
        xraw=`cat $d/in_accel_x_raw`
        yraw=`cat $d/in_accel_y_raw`
        zraw=`cat $d/in_accel_z_raw`


        printf "Value read: X (raw/scale)  %d / %.06f \n" $xraw $rscale
        printf "Value read: Y (raw/scale)  %d / %.06f \n" $yraw $rscale
        printf "Value read: Z (raw/scale)  %d / %.06f \n" $zraw $rscale

        factor=`echo "scale=2;256.0 / 9.81" | bc`
        xval=`echo "scale=2;$xraw*$rscale*$factor" | bc`
        yval=`echo "scale=2;$yraw*$rscale*$factor" | bc`
        zval=`echo "scale=2;$zraw*$rscale*$factor" | bc`

        printf "Accelerometer value: [ %.02f, %.02f, %.02f ]\n" $xval $yval $zval
    fi

    # for lsm6dsl: gyroscope
    if grep -q lsm6dsl_gyro $d/name ;
    then
        echo "============================="
        echo "===      LSM6DSL          ==="
        echo "===    (gyroscope)        ==="
        echo "============================="
        rscale=`cat $d/in_anglvel_scale`
        xraw=`cat $d/in_anglvel_x_raw`
        yraw=`cat $d/in_anglvel_y_raw`
        zraw=`cat $d/in_anglvel_z_raw`

        printf "Value read: X (raw/scale)  %d / %.06f \n" $xraw $rscale
        printf "Value read: Y (raw/scale)  %d / %.06f \n" $yraw $rscale
        printf "Value read: Z (raw/scale)  %d / %.06f \n" $zraw $rscale

        factor=`echo "scale=2;256.0 / 9.81" | bc`
        xval=`echo "scale=2;$xraw*$rscale*$factor" | bc`
        yval=`echo "scale=2;$yraw*$rscale*$factor" | bc`
        zval=`echo "scale=2;$zraw*$rscale*$factor" | bc`

        printf "Gyroscope value: [ %.02f, %.02f, %.02f ]\n" $xval $yval $zval
    fi
done

5. Read motion MEMS via Python script[edit source]

The goal of this section is to read the informations provided by Linux kernel interface and process it with a python script.
The python displays the calculated value through a graphic user interface.

5.1. Display a window with Python and weston/wayland[edit source]

#!/usr/bin/python3
import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk
from gi.repository import GObject
from gi.repository import Gdk
from gi.repository import GLib
from gi.repository import GdkPixbuf
import cairo

import random
import math
import os
from time import sleep, time

# -------------------------------------------------------------------
# -------------------------------------------------------------------
class MainUIWindow(Gtk.Window):
    def __init__(self):
        Gtk.Window.__init__(self, title="Sensor usage")
        #self.set_decorated(False)
        self.maximize()
        self.screen_width = self.get_screen().get_width()
        self.screen_height = self.get_screen().get_height()

        self.set_default_size(self.screen_width, self.screen_height)
        print("[DEBUG] screen size: %dx%d" % (self.screen_width, self.screen_height))
        self.set_position(Gtk.WindowPosition.CENTER)
        self.connect('destroy', Gtk.main_quit)

    def destroy(self, widget, data=None):
        Gtk.main_quit()

# -------------------------------------------------------------------
# -------------------------------------------------------------------
# Main
if __name__ == "__main__":
    # add signal to catch CRTL+C
    import signal
    signal.signal(signal.SIGINT, signal.SIG_DFL)
    win = MainUIWindow()
    win.connect("delete-event", Gtk.main_quit)
    win.show_all()

    Gtk.main()

5.2. Read temperature[edit source]

Part of code for reading temperature with HTS221 driver:

def found_iio_device_with_name(data, name):
    prefix = "/sys/bus/iio/devices/"
    of_name = 'OF_NAME=' + name
    try:
        for filefolder in os.listdir(prefix):
            with open(prefix + '/' + filefolder + '/uevent') as f:
                for line in f:
                    if line.split('\n')[0] == of_name:
                        ''' return directory which contains "data" '''
                        if os.path.exists(prefix + '/' + filefolder + '/' + data):
                            return (prefix + '/' + filefolder + '/')
    except OSError:
        pass
    except Exception as exc:
        pass
    return None

prefix_path = found_iio_device_with_name("in_temp_raw", "hts221")
try:
    with open(prefix_path + "in_temp_" + 'raw', 'r') as f:
        raw = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_temp_" + 'raw', exc)
    raw = 0.0

try:
    with open(prefix_path + "in_temp_" + 'scale', 'r') as f:
        scale = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_temp_" + 'scale', exc)
    scale = 0.0

try:
    with open(prefix_path + "in_temp_" + 'offset', 'r') as f:
        offset = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_temp_" + 'offset', exc)
    offset = 0.0

temp = (offset + raw) * scale

5.3. Read humidity[edit source]

Part of code for reading humidity with HTS221 driver:

def found_iio_device_with_name(data, name):
    prefix = "/sys/bus/iio/devices/"
    of_name = 'OF_NAME=' + name
    try:
        for filefolder in os.listdir(prefix):
            with open(prefix + '/' + filefolder + '/uevent') as f:
                for line in f:
                    if line.split('\n')[0] == of_name:
                        ''' return directory which contains "data" '''
                        if os.path.exists(prefix + '/' + filefolder + '/' + data):
                            return (prefix + '/' + filefolder + '/')
    except OSError:
        pass
    except Exception as exc:
        pass
    return None

prefix_path = found_iio_device_with_name("in_humidityrelative_raw", "hts221")
try:
    with open(prefix_path + "in_humidityrelative_" + 'raw', 'r') as f:
        raw = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_humidityrelative_" + 'raw', exc)
    raw = 0.0

try:
    with open(prefix_path + "in_humidityrelative_" + 'scale', 'r') as f:
        scale = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_humidityrelative_" + 'scale', exc)
    scale = 0.0

try:
    with open(prefix_path + "in_humidityrelative_" + 'offset', 'r') as f:
        offset = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_humidityrelative_" + 'offset', exc)
    offset = 0.0

humidity = (offset + raw) * scale

5.4. Read accelerometer[edit source]

Part of code for reading accelerometer with LSM6DSL driver:

def found_iio_device_with_name(data, name):
    prefix = "/sys/bus/iio/devices/"
    of_name = 'OF_NAME=' + name
    try:
        for filefolder in os.listdir(prefix):
            with open(prefix + '/' + filefolder + '/uevent') as f:
                for line in f:
                    if line.split('\n')[0] == of_name:
                        ''' return directory which contains "data" '''
                        if os.path.exists(prefix + '/' + filefolder + '/' + data):
                            return (prefix + '/' + filefolder + '/')
    except OSError:
        pass
    except Exception as exc:
        pass
    return None

prefix_path = found_iio_device_with_name("in_accel_x_raw", "lsm6dsl")
try:
    with open(prefix_path + "in_accel_" + 'x_raw', 'r') as f:
        xraw = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_accel_" + 'x_raw', exc)
    xraw = 0.0

try:
    with open(prefix_path + "in_accel_" + 'scale', 'r') as f:
        rscale = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_accel_" + 'scale', exc)
    rscale = 0.0
accel_x = int(xraw * rscale * 256.0 / 9.81)

try:
    with open(prefix_path + "in_accel_" + 'y_raw', 'r') as f:
        yraw = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_accel_" + 'y_raw', exc)
    yraw = 0.0

accel_y = int(yraw * rscale * 256.0 / 9.81)

try:
    with open(prefix_path + "in_accel_" + 'z_raw', 'r') as f:
        zraw = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_accel_" + 'z_raw', exc)
    zraw = 0.0

accel_z = int(zraw * rscale * 256.0 / 9.81)

5.5. Read gyroscope[edit source]

Part of code for reading gyroscope with LSM6DSL driver:

def found_iio_device_with_name(data, name):
    prefix = "/sys/bus/iio/devices/"
    of_name = 'OF_NAME=' + name
    try:
        for filefolder in os.listdir(prefix):
            with open(prefix + '/' + filefolder + '/uevent') as f:
                for line in f:
                    if line.split('\n')[0] == of_name:
                        ''' return directory which contains "data" '''
                        if os.path.exists(prefix + '/' + filefolder + '/' + data):
                            return (prefix + '/' + filefolder + '/')
    except OSError:
        pass
    except Exception as exc:
        pass
    return None

prefix_path = found_iio_device_with_name("in_anglvel_x_raw", "lsm6dsl")
try:
    with open(prefix_path + "in_anglvel_" + 'scale', 'r') as f:
        rscale = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'scale', exc)
    rscale = 0.0

try:
    with open(prefix_path + "in_anglvel_" + 'x_raw', 'r') as f:
        xraw = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'x_raw', exc)
    xraw = 0.0

gyro_x = int(xraw * rscale * 256.0 / 9.81)

try:
    with open(prefix_path + "in_anglvel_" + 'y_raw', 'r') as f:
        yraw = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'y_raw', exc)
    yraw = 0.0

gyro_y = int(yraw * rscale * 256.0 / 9.81)

try:
    with open(prefix_path + "in_anglvel_" + 'z_raw', 'r') as f:
        zraw = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'z_raw', exc)
    zraw = 0.0

gyro_z = int(zraw * rscale * 256.0 / 9.81)

5.6. Full script with information displayed in a graphic user interface[edit source]

#!/usr/bin/python3
import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk
from gi.repository import GObject
from gi.repository import Gdk
from gi.repository import GLib
from gi.repository import GdkPixbuf
import cairo

import random
import math
import os
from time import sleep, time

# time between each sensor mesearuement (1s)
TIME_UPATE = 2000


class Sensors():
    def __init__(self):
        ''' '''
        self.sensor_dictionnary = {}

    def found_iio_device_with_name(self, data, name):
        prefix = "/sys/bus/iio/devices/"
        of_name = 'OF_NAME=' + name
        try:
            for filefolder in os.listdir(prefix):
                with open(prefix + '/' + filefolder + '/uevent') as f:
                    for line in f:
                        if line.split('\n')[0] == of_name:
                            ''' return directory which contains "data" '''
                            if os.path.exists(prefix + '/' + filefolder + '/' + data):
                                return (prefix + '/' + filefolder + '/')
        except OSError:
            pass
        except Exception as exc:
            pass
        return None

    def found_all_sensor_path(self):
        self.sensor_dictionnary['temperature'] = self.found_iio_device_with_name("in_temp_raw", "hts221")
        self.sensor_dictionnary['humidity']    = self.found_iio_device_with_name("in_humidityrelative_raw", "hts221")
        self.sensor_dictionnary['accelerometer'] = self.found_iio_device_with_name("in_accel_x_raw", "lsm6dsl")
        self.sensor_dictionnary['gyroscope'] = self.found_iio_device_with_name("in_anglvel_x_raw", "lsm6dsl")

        print("[DEBUG] temperature   -> ", self.sensor_dictionnary['temperature'], "<")
        print("[DEBUG] humidity      -> ", self.sensor_dictionnary['humidity'], "<")
        print("[DEBUG] accelerometer -> ", self.sensor_dictionnary['accelerometer'], "<")
        print("[DEBUG] gyroscope     -> ", self.sensor_dictionnary['gyroscope'], "<")

    def temperature_read(self):
        prefix_path = self.sensor_dictionnary['temperature']
        try:
            with open(prefix_path + "in_temp_" + 'raw', 'r') as f:
                raw = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_temp_" + 'raw', exc)
            raw = 0.0
        try:
            with open(prefix_path + "in_temp_" + 'scale', 'r') as f:
                scale = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_temp_" + 'scale', exc)
            scale = 0.0
        try:
            with open(prefix_path + "in_temp_" + 'offset', 'r') as f:
                offset = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_temp_" + 'offset', exc)
            offset = 0.0
        return (offset + raw) * scale

    def humidity_read(self):
        prefix_path = self.sensor_dictionnary['humidity']
        try:
            with open(prefix_path + "in_humidityrelative_" + 'raw', 'r') as f:
                raw = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_humidityrelative_" + 'raw', exc)
            raw = 0.0
        try:
            with open(prefix_path + "in_humidityrelative_" + 'scale', 'r') as f:
                scale = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_humidityrelative_" + 'scale', exc)
            scale = 0.0
        try:
            with open(prefix_path + "in_humidityrelative_" + 'offset', 'r') as f:
                offset = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_humidityrelative_" + 'offset', exc)
            offset = 0.0
        return (offset + raw) * scale

    def accelerometer_read(self):
        prefix_path = self.sensor_dictionnary['accelerometer']
        try:
            with open(prefix_path + "in_accel_" + 'scale', 'r') as f:
                rscale = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_accel_" + 'scale', exc)
            rscale = 0.0

        try:
            with open(prefix_path + "in_accel_" + 'x_raw', 'r') as f:
                xraw = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_accel_" + 'x_raw', exc)
            xraw = 0.0

        accel_x = int(xraw * rscale * 256.0 / 9.81)
        try:
            with open(prefix_path + "in_accel_" + 'y_raw', 'r') as f:
                yraw = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_accel_" + 'y_raw', exc)
            yraw = 0.0

        accel_y = int(yraw * rscale * 256.0 / 9.81)
        try:
            with open(prefix_path + "in_accel_" + 'z_raw', 'r') as f:
                zraw = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_accel_" + 'z_raw', exc)
            zraw = 0.0

        accel_z = int(zraw * rscale * 256.0 / 9.81)
        return [ accel_x, accel_y, accel_z]

    def gyroscope_read(self):
        prefix_path = self.sensor_dictionnary['gyroscope']
        try:
            with open(prefix_path + "in_anglvel_" + 'scale', 'r') as f:
                rscale = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'scale', exc)
            rscale = 0.0
        try:
            with open(prefix_path + "in_anglvel_" + 'x_raw', 'r') as f:
                xraw = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'x_raw', exc)
            xraw = 0.0

        gyro_x = int(xraw * rscale * 256.0 / 9.81)
        try:
            with open(prefix_path + "in_anglvel_" + 'y_raw', 'r') as f:
                yraw = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'y_raw', exc)
            yraw = 0.0
        gyro_y = int(yraw * rscale * 256.0 / 9.81)
        try:
            with open(prefix_path + "in_anglvel_" + 'z_raw', 'r') as f:
                zraw = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'z_raw', exc)
            zraw = 0.0
        gyro_z = int(zraw * rscale * 256.0 / 9.81)
        return [ gyro_x, gyro_y, gyro_z]

# -------------------------------------------------------------------
# -------------------------------------------------------------------
class MainUIWindow(Gtk.Window):
    def __init__(self):
        Gtk.Window.__init__(self, title="Sensor usage")
        #self.set_decorated(False)
        self.maximize()
        self.screen_width = self.get_screen().get_width()
        self.screen_height = self.get_screen().get_height()

        self.set_default_size(self.screen_width, self.screen_height)
        print("[DEBUG] screen size: %dx%d" % (self.screen_width, self.screen_height))
        self.set_position(Gtk.WindowPosition.CENTER)
        self.connect('destroy', Gtk.main_quit)

        # search sensor interface
        self.sensors = Sensors()
        self.sensors.found_all_sensor_path()

        sensor_box = Gtk.VBox(homogeneous=False, spacing=0)

        # temperature
        temp_label = Gtk.Label()
        temp_label.set_markup("<span font_desc='LiberationSans 25'>Temperature</span>")
        self.temp_value_label = Gtk.Label()
        self.temp_value_label.set_markup("<span font_desc='LiberationSans 25'>--.-- °C</span>")
        temp_box = Gtk.HBox(homogeneous=False, spacing=0)
        temp_box.add(temp_label)
        temp_box.add(self.temp_value_label)
        sensor_box.add(temp_box)

        # humidity
        humidity_label = Gtk.Label()
        humidity_label.set_markup("<span font_desc='LiberationSans 25'>Humidity</span>")
        self.humidity_value_label = Gtk.Label()
        self.humidity_value_label.set_markup("<span font_desc='LiberationSans 25'>--.-- %c</span>" % '%')
        humidity_box = Gtk.HBox(homogeneous=False, spacing=0)
        humidity_box.add(humidity_label)
        humidity_box.add(self.humidity_value_label)
        sensor_box.add(humidity_box)

        # Accel
        accel_label = Gtk.Label()
        accel_label.set_markup("<span font_desc='LiberationSans 25'>Accelerometer</span>")
        self.accel_value_label = Gtk.Label()
        self.accel_value_label.set_markup("<span font_desc='LiberationSans 25'> [ --.--, --.--, --.--]</span>")
        accel_box = Gtk.HBox(homogeneous=False, spacing=0)
        accel_box.add(accel_label)
        accel_box.add(self.accel_value_label)
        sensor_box.add(accel_box)

        # Gyroscope
        gyro_label = Gtk.Label()
        gyro_label.set_markup("<span font_desc='LiberationSans 25'>Gyroscope</span>")
        self.gyro_value_label = Gtk.Label()
        self.gyro_value_label.set_markup("<span font_desc='LiberationSans 25'> [ --.--, --.--, --.--]</span>")
        gyro_box = Gtk.HBox(homogeneous=False, spacing=0)
        gyro_box.add(gyro_label)
        gyro_box.add(self.gyro_value_label)
        sensor_box.add(gyro_box)

        self.add(sensor_box)

        # Add a timer callback to update
        # this takes 2 args: (how often to update in millisec, the method to run)
        GLib.timeout_add(TIME_UPATE, self.update_ui)


    def destroy(self, widget, data=None):
        Gtk.main_quit()


    def update_ui(self, user_data):
        # temperature
        temp = self.sensors.temperature_read()
        self.temp_value_label.set_markup("<span font_desc='LiberationSans 25'>%.02f °C</span>" % temp)
        # humidity
        hum = self.sensors.humidity_read()
        self.humidity_value_label.set_markup("<span font_desc='LiberationSans 25'>%.02f %c</span>" % (hum, '%'))
        # accel
        accel = self.sensors.accelerometer_read()
        self.accel_value_label.set_markup("<span font_desc='LiberationSans 25'>[ %.02f, %.02f, %.02f]</span>" % (accel[0], accel[1], accel[2]))
        # gyro
        gyro = self.sensors.gyroscope_read()
        self.gyro_value_label.set_markup("<span font_desc='LiberationSans 25'>[ %.02f, %.02f, %.02f]</span>" % (gyro[0], gyro[1], gyro[2]))

        # As this is a timeout function, return True so that it
        # continues to get called
        return True


# -------------------------------------------------------------------
# -------------------------------------------------------------------
# Main
if __name__ == "__main__":
    # add signal to catch CRTL+C
    import signal
    signal.signal(signal.SIGINT, signal.SIG_DFL)
    win = MainUIWindow()
    win.connect("delete-event", Gtk.main_quit)
    win.show_all()

    Gtk.main()