IKS01Ax MEMS expansion board

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1. Article purpose[edit source]

The purpose of this article is to explain how to integrate the IKS01A expansion board with STM32MP157C-DK2. IKS01A expansion is a motion MEMS and environmental sensor expansion board.
This article will explain step by step how to support IKS01A expansion board on Linux part of software and describe how to use several motion MEMS like HTS221 and LSM6DX.

2. Pre-requisite[edit source]

2.1. Hardware[edit source]

  • STM32MP157C-DK2
STM32MP157C-DK2 recto

For more information about hardware and how to start it: link

  • IKS01A2 expansion board
IKS01A2
IKS01A2

2.2. Software[edit source]

For the software, please follow all step described on [start for STM32MP157C-DK2]

3. Software customization for supporting IKS01A expansion board[edit source]

For using IKS01A expansion board you need to configure the kernel with some device tree add-ons and kernel configuration.

3.1. Kernel configuration[edit source]

By default the motions MEMS driver present on IKS01A expansion board are supported: hts221, pressure(lp22hb) and lsm6dsl

To verify if the kernel have this driver, at runtime on board , the configuration of kernel available: 

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

$BOARD> 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

$BOARD> 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

3.2. Kernel device tree[edit source]

The IKS01A expansion board are use via the IC2 bus and on STM32MP157C-DK2 this I2C bus associated are I2C5.
On device tree of STM32MP157C-DK2, the I2C5 must be activated and contains the entry for each hardware to support. Content to add in stm32mp157c-dk2.dts: 

 &i2c5 {
	pinctrl-names = "default", "sleep";
	pinctrl-0 = <&i2c5_pins_a>;
	pinctrl-1 = <&i2c5_pins_sleep_a>;
	i2c-scl-rising-time-ns = <124>;
	i2c-scl-falling-time-ns = <3>;
	/delete-property/dmas;
	/delete-property/dma-names;

	status = "okay";

	hts221@5f {
		compatible = "st,hts221";
		reg = <0x5f>;
	};
	lsm6dsl@6b {
		compatible = "st,lsm6dsl";
		reg = <0x6b>;
	};
 };
Info white.png Information
Do regenerate a device tree, please follow the indication of [Modify, rebuild and reload the Linux® kernel]

3.3. Activate new configuration on board[edit source]

  • Pre-requisite: you need to have re-generated your device tree and your kernel.
  • Please put the two file on file system of board, on bootfs partition (/boot directory)
$BOARD>  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 an entry on extlinux.conf file, here on /boot/mmc0_stm32mp157c-dk2_extlinux/extlinux.conf or if there is no mmc0-<something> available on /boot/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 stm32mp157c-dk2-sdcard
         KERNEL /uImage
         FDT /stm32mp157c-dk2.dtb
         APPEND root=/dev/mmcblk0p6 rootwait rw console=ttySTM0,115200
 LABEL stm32mp157c-dk2-a7-examples-sdcard
         KERNEL /uImage
         FDT /stm32mp157c-dk2-a7-examples.dtb
         APPEND root=/dev/mmcblk0p6 rootwait rw console=ttySTM0,115200
 LABEL stm32mp157c-dk2-m4-examples-sdcard
         KERNEL /uImage
         FDT /stm32mp157c-dk2-m4-examples.dtb
         APPEND root=/dev/mmcblk0p6 rootwait rw console=ttySTM0,115200
 LABEL stm32mp157c-dk2-iks01a2
        KERNEL /uImage
        FDT /stm32mp157c-dk2-iks01a2.dtb
        APPEND root=/dev/mmcblk0p6 rootwait rw console=ttySTM0,115200
Warning white.png Warning
don't forget to synchronize the filesystem before to reboot the board
$BOARD> sync
  • Reboot the board

3.4. Verify new configuration on board[edit source]

  • Verify if i2c5 are enable:
$BOARD> cat /proc/device-tree/soc/i2c\@40015000/status 
okay
  • Verify if motions MEMS driver are declared on device tree node:
$BOARD> ls -l /proc/device-tree/soc/i2c\@40015000/
total 0
-r--r--r-- 1 root root  4 Dec 19 11:01 #address-cells
-r--r--r-- 1 root root  4 Dec 19 11:01 #size-cells
-r--r--r-- 1 root root  8 Dec 19 11:01 clocks
-r--r--r-- 1 root root 15 Dec 19 11:01 compatible
-r--r--r-- 1 root root  6 Dec 19 11:01 dma-names
-r--r--r-- 1 root root 32 Dec 19 11:01 dmas
drwxr-xr-x 2 root root  0 Dec 19 10:54 hts221@5f
-r--r--r-- 1 root root  4 Dec 19 11:01 i2c-scl-falling-time-ns
-r--r--r-- 1 root root  4 Dec 19 11:01 i2c-scl-rising-time-ns
-r--r--r-- 1 root root 19 Dec 19 11:01 interrupt-names
-r--r--r-- 1 root root 44 Dec 19 11:01 interrupts-extended
drwxr-xr-x 2 root root  0 Dec 19 10:54 lsm6dsl@6b
-r--r--r-- 1 root root  4 Dec 19 11:01 name
-r--r--r-- 1 root root  4 Dec 19 11:01 pinctrl-0
-r--r--r-- 1 root root  4 Dec 19 11:01 pinctrl-1
-r--r--r-- 1 root root 14 Dec 19 11:01 pinctrl-names
-r--r--r-- 1 root root  4 Dec 19 11:01 power-domains
-r--r--r-- 1 root root  8 Dec 19 11:01 reg
-r--r--r-- 1 root root  8 Dec 19 11:01 resets
-r--r--r-- 1 root root 12 Dec 19 11:01 st,syscfg-fmp
-r--r--r-- 1 root root  5 Dec 19 11:01 status
  • Verify if the driver are probed correctly and see the hardware:
$BOARD> grep OF_NAME /sys/bus/iio/devices/iio\:device*/uevent
/sys/bus/iio/devices/iio:device0/uevent:OF_NAME=adc
/sys/bus/iio/devices/iio:device1/uevent:OF_NAME=adc
/sys/bus/iio/devices/iio:device2/uevent:OF_NAME=hts221
/sys/bus/iio/devices/iio:device3/uevent:OF_NAME=temp
/sys/bus/iio/devices/iio:device4/uevent:OF_NAME=lsm6dsl
/sys/bus/iio/devices/iio:device5/uevent:OF_NAME=lsm6dsl

4. Read Motion MEMS on Linux via Bash script[edit source]

4.1. List of sensors entry[edit source]

IKS01A2 expansion board provide several MEMS like hts221, lsm6dsl, lp22hb. The list of hardware (mems) detected by linux via IIO framework can be listed by verifying the entry on sysfs. 

$BOARD>  grep OF_NAME /sys/bus/iio/devices/iio\:device*/uevent
/sys/bus/iio/devices/iio:device0/uevent:OF_NAME=adc
/sys/bus/iio/devices/iio:device1/uevent:OF_NAME=adc
/sys/bus/iio/devices/iio:device2/uevent:OF_NAME=hts221
/sys/bus/iio/devices/iio:device3/uevent:OF_NAME=temp
/sys/bus/iio/devices/iio:device4/uevent:OF_NAME=lsm6dsl
/sys/bus/iio/devices/iio:device5/uevent:OF_NAME=lsm6dsl

This list of entries permit to know on which entry are associated a MEMS driver. In the rest of the article, we will keep this list as reference list of entries.

4.2. HTS221: Temperature/Humidity[edit source]

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

In this example hts221 entry are /sys/bus/iio/devices/iio:device2/.

4.2.1. Temperature[edit source]

  • Read entry associated to temperature for HTS221 driver
$BOARD> cat /sys/bus/iio/devices/iio\:device2/in_temp_raw
$BOARD> cat /sys/bus/iio/devices/iio\:device2/in_temp_offset
$BOARD> cat /sys/bus/iio/devices/iio\:device2/in_temp_scale
  • Calculate real temperature:
Temperature = ( Raw value + Offset value) * Scale value)
  • Calculate temperature by shell script

Content of hts221_read_temperature.sh: 

#!/bin/sh
raw=`cat /sys/bus/iio/devices/iio\:device2/in_temp_raw`
offset=`cat /sys/bus/iio/devices/iio\:device2/in_temp_offset`
scale=`cat /sys/bus/iio/devices/iio\:device2/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
  • Test on board
$BOARD> ./hts221_read_temperature.sh
Value read: raw         563.000000
Value read: offset      1036.674817
Value read: scale       0.019172
Temperature 30.668765624
Temperature 30.67

4.2.2. Humidity[edit source]

  • Read entry associated to humidity for HTS221 driver
$BOARD> cat /sys/bus/iio/devices/iio\:device2/in_humidityrelative_raw
$BOARD> cat /sys/bus/iio/devices/iio\:device2/in_humidityrelative_offset
$BOARD> cat /sys/bus/iio/devices/iio\:device2/in_humidityrelative_scale
  • Calculate real humidity
Humidity = ( Raw value + Offset value) * Scale value)
  • Calculate humidity by shell script

Content of hts221_read_humidity.sh: 

#!/bin/sh
raw=`cat /sys/bus/iio/devices/iio\:device2/in_humidityrelative_raw`
offset=`cat /sys/bus/iio/devices/iio\:device2/in_humidityrelative_offset`
scale=`cat /sys/bus/iio/devices/iio\:device2/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
  • Test on board
$BOARD> ./hts221_read_humidity.sh
Value read: raw         2669.000000
Value read: offset      -10661.500000
Value read: scale       -0.003000
Humidity 23.977500000
Humidity 23.98

4.3. LSM6DSL: Accelerometer/Gyroscope[edit source]

LSM6DSL is an inertial measurement unit (IMU), for smart phones and battery operated IoT, Gaming, Wearable and Consumer Electronics. Ultra-low power and high accuracy.

In this example lsm6dsl entry are /sys/bus/iio/devices/iio:device4/ and /sys/bus/iio/devices/iio:device4/.
Device4 entry are dedicated Accelerometer and device5 for gyroscope.

4.3.1. Accelerometer[edit source]

  • Read entry associated to Accelerometer for LSM6DSL driver
$BOARD> cat /sys/bus/iio/devices/iio\:device4/in_accel_x_raw
$BOARD> cat /sys/bus/iio/devices/iio\:device4/in_accel_x_scale
$BOARD> cat /sys/bus/iio/devices/iio\:device4/in_accel_y_raw
$BOARD> cat /sys/bus/iio/devices/iio\:device4/in_accel_y_scale
$BOARD> cat /sys/bus/iio/devices/iio\:device4/in_accel_z_raw
$BOARD> cat /sys/bus/iio/devices/iio\:device4/in_accel_z_scale
  • Calculate accelerometer value:
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 accel value by shell script

Content of lsm6dsl_accel_read.sh: 

#!/bin/sh
xraw=`cat /sys/bus/iio/devices/iio\:device4/in_accel_x_raw`
xscale=`cat /sys/bus/iio/devices/iio\:device4/in_accel_x_scale`

yraw=`cat /sys/bus/iio/devices/iio\:device4/in_accel_y_raw`
yscale=`cat /sys/bus/iio/devices/iio\:device4/in_accel_y_scale`

zraw=`cat /sys/bus/iio/devices/iio\:device4/in_accel_z_raw`
zscale=`cat /sys/bus/iio/devices/iio\:device4/in_accel_z_scale`

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

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

printf "Accelerometer value: [ %.02f, %.02f, %.02f ]\n" $xval $yval $zval
  • Test on board
$BOARD> ./lsm6dsl_accel_read.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 entry associated to Gyroscope for LSM6DSL driver
$BOARD> cat /sys/bus/iio/devices/iio\:device5/in_anglvel_x_raw
$BOARD> cat /sys/bus/iio/devices/iio\:device5/in_anglvel_x_scale
$BOARD> cat /sys/bus/iio/devices/iio\:device5/in_anglvel_y_raw
$BOARD> cat /sys/bus/iio/devices/iio\:device5/in_anglvel_y_scale
$BOARD> cat /sys/bus/iio/devices/iio\:device5/in_anglvel_z_raw
$BOARD> cat /sys/bus/iio/devices/iio\:device5/in_anglvel_z_scale
  • Calculate gyroscope value:
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

Content of lsm6dsl_gyro_read.sh: 

#!/bin/sh
xraw=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_x_raw`
xscale=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_x_scale`

yraw=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_y_raw`
yscale=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_y_scale`

zraw=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_z_raw`
zscale=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_z_scale`

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

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

printf "Gyroscope value: [ %.02f, %.02f, %.02f ]\n" $xval $yval $zval
  • Test on board
$BOARD> ./lsm6dsl_gyro_read.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 measurement[edit source]

Content of iks01a2.sh 

#!/bin/sh
echo "============================="
echo "===       HTS221          ==="
echo "===    (temperature)      ==="
echo "============================="
raw=`cat /sys/bus/iio/devices/iio\:device2/in_temp_raw`
offset=`cat /sys/bus/iio/devices/iio\:device2/in_temp_offset`
scale=`cat /sys/bus/iio/devices/iio\:device2/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\:device2/in_humidityrelative_raw`
offset=`cat /sys/bus/iio/devices/iio\:device2/in_humidityrelative_offset`
scale=`cat /sys/bus/iio/devices/iio\:device2/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 "============================="

xraw=`cat /sys/bus/iio/devices/iio\:device4/in_accel_x_raw`
xscale=`cat /sys/bus/iio/devices/iio\:device4/in_accel_x_scale`

yraw=`cat /sys/bus/iio/devices/iio\:device4/in_accel_y_raw`
yscale=`cat /sys/bus/iio/devices/iio\:device4/in_accel_y_scale`

zraw=`cat /sys/bus/iio/devices/iio\:device4/in_accel_z_raw`
zscale=`cat /sys/bus/iio/devices/iio\:device4/in_accel_z_scale`

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

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

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

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

xraw=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_x_raw`
xscale=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_x_scale`

yraw=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_y_raw`
yscale=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_y_scale`

zraw=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_z_raw`
zscale=`cat /sys/bus/iio/devices/iio\:device5/in_anglvel_z_scale`

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

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

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

5. Read Motion MEMS on Linux via Python script[edit source]

5.1. Display a windows 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]

Only a 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]

Only a 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]

Only a 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_" + 'x_scale', 'r') as f:
        xscale = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_accel_" + 'x_scale', exc)
    xscale = 0.0
accel_x = int(xraw * xscale * 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

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

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

5.5. Read gyroscope[edit source]

Only a 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_" + '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

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

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

try:
    with open(prefix_path + "in_anglvel_" + 'z_scale', 'r') as f:
        zscale = float(f.read())
except Exception as exc:
    print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'z_scale', exc)
    zscale = 0.0
gyro_z = int(zraw * zscale * 256.0 / 9.81)

5.6. Full script with information displayed on a windows[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_" + '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_" + 'x_scale', 'r') as f:
                xscale = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_accel_" + 'x_scale', exc)
            xscale = 0.0
        accel_x = int(xraw * xscale * 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
        try:
            with open(prefix_path + "in_accel_" + 'y_scale', 'r') as f:
                yscale = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_accel_" + 'y_scale', exc)
            yscale = 0.0
        accel_y = int(yraw * yscale * 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
        try:
            with open(prefix_path + "in_accel_" + 'z_scale', 'r') as f:
                zscale = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_accel_" + 'z_scale', exc)
            zscale = 0.0
        accel_z = int(zraw * zscale * 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_" + '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
        try:
            with open(prefix_path + "in_anglvel_" + 'x_scale', 'r') as f:
                xscale = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'x_scale', exc)
            xscale = 0.0
        gyro_x = int(xraw * xscale * 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
        try:
            with open(prefix_path + "in_anglvel_" + 'y_scale', 'r') as f:
                yscale = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'y_scale', exc)
            yscale = 0.0
        gyro_y = int(yraw * yscale * 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
        try:
            with open(prefix_path + "in_anglvel_" + 'z_scale', 'r') as f:
                zscale = float(f.read())
        except Exception as exc:
            print("[ERROR] read %s " % prefix_path + "in_anglvel_" + 'z_scale', exc)
            zscale = 0.0
        gyro_z = int(zraw * zscale * 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(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(False, 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(False, 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(False, 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(False, 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)
        self.timer = GObject.timeout_add(TIME_UPATE, self.update_ui, None)
        self.timer_enable = True


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


    def update_ui(self, user_data):
        if False == self.timer_enable:
            return False;
        # 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()
  • Screenshot
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5.7. Example of screenshot for displaying information[edit source]

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Linux® is a registered trademark of Linus Torvalds.

Inter-integrated circuit (Bi-directional 2-wire bus standard for efficient inter-IC control.)

Serial peripheral interface

Industrial I/O Linux® subsystem

System file system (see https://en.wikipedia.org/wiki/Sysfs for more details)

Inertial measurement unit

Internet of things

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