IOT-GATE-iMX7 and SBC-IOT-iMX7: Yocto Linux: User Space

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The example run-time Yocto Linux filesystem image for the IOT-GATE-iMX7 IoT Gateway and SBC-IOT-iMX7 Single Board Computer is based on NXP Community Yocto Project BSP for i.MX based boards.

Creating Live SD-card article provides a brief introduction on how to create and use the live Yocto Live-SD card.

Admolition note.png The article uses cl-rootfs hostname. A real hostname may be different.

Using Yocto Linux

Connection and Logging In

Use the root username to login:

cl-rootfs login: root


The networking configuration in the example Yocto Linux image is almost the same as in the Debian Linux image.

Analog Audio

Use aplay -l to list all sound cards and digital audio devices registered on the system:

root@cl-rootfs:~# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: clsomimx7 [cl-som-imx7], device 0: 308a0000.sai-wm8731-hifi wm8731-hifi-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0

Analog Audio Playback

In order to play back a sound file make use of the aplay application.

  • aplay -L can be used for listing of all pcm devices.

Here is a sample output of aplay -L command:

root@cl-rootfs:~# aplay -L
    Discard all samples (playback) or generate zero samples (capture)
    Default Audio Device
    Default Audio Device
    Direct sample mixing device
    Direct sample snooping device
    Direct hardware device without any conversions
    Hardware device with all software conversions

The next command can be used for audio play back:

root@cl-rootfs:~# aplay -D sysdefault <wav-file>

Audio Input Settings

CL-SOM-iMX7 provides an audio capturing feature from either Mic or Line In input sources. alsamixer or amixer can be used in order to switch between these inputs.

  • alsamixer
Capture Volume => 100
Line Capture Switch => off
Mic Capture Switch => on
Input Mux => Mic
  • amixer
amixer cset numid=1 65536
amixer -c 0 cset numid=3 31,31
amixer -c 0 cset numid=4 0
amixer -c 0 cset numid=6 1
amixer -c 0 cset numid=14 1
Line In
  • alsamixer
Capture Volume => 100
Line Capture Switch => on
Mic Capture Switch => off
Input Mux => Line In
  • amixer
amixer cset numid=1 65536
amixer -c 0 cset numid=3 31
amixer -c 0 cset numid=4 1
amixer -c 0 cset numid=6 0
amixer -c 0 cset numid=14 0

Sample Audio Recording

As soon as the correct input values have been set, audio signal can be captured. Here is a sample command that shows the arecord usage for capturing audio signal from the selected input line.

root@cl-rootfs:~# arecord -D sysdefault -d 10 -f dat -t wav /tmp/out.wav


CL-SOM-iMX7 features 802.11b/g/n wireless connectivity solution, implemented with a TI WiLink8 Combo module. The device driver name is wl18xx.
By default all wireless interfaces are soft blocked. Use the rfkill utility to block/unblock wireless interfaces and display their status.

WiFi Initialization

  • WiFi requires no user interaction for being configured. The driver gets loaded automatically.

Make sure that the WiFi driver is loaded:

root@cl-som-imx7:~# lsmod | grep wl18xx
wl18xx                 70950  0

The WiFi driver can be loaded manually:

root@cl-som-imx7:~# modprobe wl18xx
	wlcore: ERROR could not get configuration binary ti-connectivity/wl18xx-conf.bin: -2
	wlcore: WARNING falling back to default config
	wlcore: wl18xx HW: 183x or 180x, PG 2.2 (ROM 0x11)
	wlcore: loaded
  • iwconfig command from wireless-tools package can be used to retrieve detailed information about the WiFi interfaces:
root@cl-som-imx7:~# iwconfig wlan0
wlan0     IEEE 802.11  ESSID:off/any
          Mode:Managed  Access Point: Not-Associated   Tx-Power=0 dBm
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:on
  • Unblock the interface:
root@cl-som-imx7:~# rfkill unblock wifi
wlcore: PHY firmware version: Rev
wlcore: firmware booted (Rev
IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
  • Activate the interface:
root@cl-som-imx7:~# ifconfig wlan0 up
  • Sample WiFi scanning:
root@cl-som-imx7:~# iwlist wlan0 scan

The output will show the list of Access Points and Ad-Hoc cells in range. For more information about connecting to wireless networks and tuning WiFi interfaces refer to “wpa_supplicant” and “wireless-tools” man pages.


  • Configure wpa_supplicant to connect to SSID with no key management. Put the network name into the "ssid" fields:
root@cl-som-imx7:~# cat << EOF > /etc/wpa_supplicant.conf
or with key management. Put the network name and the password into the "ssid/psk" fields:
root@cl-som-imx7:~# cat << EOF > /etc/wpa_supplicant.conf

  • Sample run
root@cl-som-imx7:~# ifconfig wlan0 up
root@cl-som-imx7:~# wpa_supplicant -B -Dwext -c /etc/wpa_supplicant.conf -i wlan0
root@cl-som-imx7:~# dhclient wlan0

See also