IOT-GATE-iMX7 and SBC-IOT-iMX7: Linux: Debian

Overview

The example run-time Linux filesystem image for the CompuLab IOT-GATE-iMX7 Internet of Things Gateway and SBC-IOT-iMX7 Internet of Things Single Board Computer is based on Debian GNU/Linux Sid. The CompuLab Linux package for IOT-GATE-iMX7 and SBC-IOT-iMX7 includes ready to run image, Linux kernel configuration and source code patches, and an archive of the root filesystem, used to create the image.

The default Debian Wheezy Linux image includes more than 400 software packages. Among them:

Core system
Debian package management system
X11 Windowing System
Fluxbox desktop manager
SSH server and client
PulseAudio configuration and usage utilities
Bluez5 Bluetooth tools and daemons

The Automatic Linux installation on IOT-GATE-iMX7 and SBC-IOT-iMX7 page provides a brief introduction on how to install the run-time Linux image. This article describes package structure and peripheral device options specific to IOT-GATE-iMX7 and SBC-IOT-iMX7.

Using Debian Linux on SBC-IOT-iMX7

Connection and Logging In

This Debian rootfs comes with a default sudo user compulab:

Debian GNU/Linux 10 cl-debian ttymxc0

cl-debian login: compulab
Password: compulab

This Debian rootfs comes without default root password. The root password has to be set at the very first login:

Debian GNU/Linux 10 cl-debian ttymxc0

cl-debian login: root
You are required to change your password immediately (administrator enforced)
New password: 
Retype new password:

To login into the Linux system, you may use a serial console, or connect through the network (ssh), or use a keyboard and display.

Networking

To configure networking, edit /etc/network/interfaces, /etc/resolv.conf, /etc/hostname and /etc/hosts. For more information about Debian Linux network configuration read:

Network setup chapter in the Debian Reference
Network chapter in the Debian Wiki

The majority of network setup can be done via the interfaces configuration file at /etc/network/interfaces.

auto line is required for interfaces that have to be brought up at boot time.

Using DHCP to automatically configure the interface

auto eth0
allow-hotplug eth0
iface eth0 inet dhcp

Configuring the interface manually

auto eth0
    iface eth0 inet static
        address 192.168.1.170
        netmask 255.255.0.0
        gateway 192.0.0.1

Consoles

The Linux file system image is designed to suit different kernel versions and configurations. Therefore, during the operating system startup, consoles at several serial ports and LCD display are enabled. Some of these devices may not be supported, either because of kernel versions incompatibilities, or because the kernel was not configured to support these devices. systemd is able to configure most of them. Detail information can be found here:

Systemd getty generator [systemd-getty-generator]
Gettys on Serial Consoles [serial-console]

X Windows system

The CompuLab distribution contains full featured X Windows system with Fluxbox window manager. Before starting X Windows, connect USB mouse and keyboard to the system. You can run X Windows by typing startx.

Software Management

The Debian Linux image for CL-SOM-iMX7 and derived products includes all the information required to use Debian package management utilities. You can use apt-get and dpkg out of the box.

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
null
    Discard all samples (playback) or generate zero samples (capture)
default:CARD=clsomimx7
    cl-som-imx7, 
    Default Audio Device
sysdefault:CARD=clsomimx7
    cl-som-imx7, 
    Default Audio Device
dmix:CARD=clsomimx7,DEV=0
    cl-som-imx7, 
    Direct sample mixing device
dsnoop:CARD=clsomimx7,DEV=0
    cl-som-imx7, 
    Direct sample snooping device
hw:CARD=clsomimx7,DEV=0
    cl-som-imx7, 
    Direct hardware device without any conversions
plughw:CARD=clsomimx7,DEV=0
    cl-som-imx7, 
    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.

Mic

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

WiFi

CL-SOM-iMX7 features 802.11b/g/n wireless connectivity solution, implemented with a TI WiLink8 Combo module.

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-rootfs:~# lsmod | grep wl18xx
wl18xx                 70950  0

The WiFi driver can be loaded manually:

root@cl-rootfs:~# 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-rootfs:~# iwconfig wlan0
wlan0     IEEE 802.11abgn  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

Activate the interface:

root@cl-rootfs:~# ifconfig wlan0 up

Sample WiFi scanning:

root@cl-rootfs:~# 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.

wpa_supplicant

Configuration sample

Please open a wpa_supplicant configuration file bellow and put a network name and a password into the "ssid" and "psk" fields respectively.

root@cl-rootfs:~# cat /etc/wpa_supplicant.conf
ctrl_interface=/var/run/wpa_supplicant

network={
	ssid="wireless_network_name"
	key_mgmt=WPA-PSK
	psk="wireless_network_password"
}

Sample run

root@cl-rootfs:~# ifconfig wlan0 up
root@cl-rootfs:~# wpa_supplicant -B -Dwext -c /etc/wpa_supplicant.conf -i wlan0
root@cl-rootfs:~# dhclient wlan0

Bluetooth

CL-SOM-iMX7 features Bluetooth 4.1 BLE interface, implemented with a TI WiLink8 Combo module.

Host Controller Interface (HCI) Initialization

HCI requires no user interaction for being configured. The driver gets loaded automatically unless this option has been disabled by putting a black list rule for this device.

Make sure that the Bluetooth driver is loaded:

root@cl-debian:~# lsmod | grep hci_uart
hci_uart               10445  1

The Bluetooth driver can be loaded manually:

root@cl-rootfs:~# modprobe hci_uart

HCI device configuration utility can be run to retrieve detailed information about the Bluetooth interfaces:

root@cl-rootfs:~# hciconfig hci0 -a
hci0:   Type: Primary  Bus: UART
        BD Address: 3C:A3:08:A8:03:B9  ACL MTU: 1021:6  SCO MTU: 180:4
        UP RUNNING 
        RX bytes:746 acl:0 sco:0 events:49 errors:0
        TX bytes:3441 acl:0 sco:0 commands:49 errors:0
        Features: 0xff 0xfe 0x2d 0xfe 0xdb 0xff 0x7b 0x87
        Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 
        Link policy: RSWITCH HOLD SNIFF 
        Link mode: SLAVE ACCEPT 
        Name: 'cl-debian'
        Class: 0x0c0000
        Service Classes: Rendering, Capturing
        Device Class: Miscellaneous, 
        HCI Version: 4.1 (0x7)  Revision: 0x0
        LMP Version: 4.1 (0x7)  Subversion: 0xac03
        Manufacturer: Texas Instruments Inc. (13)

If the HCI device is not running, use the below command to enable the HCI device:

root@cl-rootfs:~# hciconfig hci0 up

HCI Inquire remote devices.

root@cl-rootfs:~# hcitool scan
Scanning ...

MMC/SD

The support for MMC/SD card on Compulab devices based on the NXP iMX7 SoC is built into the Linux kernel. To mount a memory card, monitor /proc/partitions to see what partitions were detected on the MMC/SD card. For example, suppose an MMC/SD partition you'd like to mount is mmcblk0p1 then:

if [ ! -d /mnt/mmcblk0p1 ]; then mkdir /mnt/mmcblk0p1; fi
mount /dev/mmcblk0p1 /mnt/mmcblk0p1

GPIO access

Linux provides simple and convenient GPIO access via sysfs interface. A GPIO should be exported using /sys/class/gpio/export. After the GPIO is exported it is possible to change its direction and value using /sys/class/gpio/gpioX/direction and /sys/class/gpio/gpioX/value attributes.

Example

The following example demonstrates how to configure GPIO 140 as output and set value to high:

root@cl-rootfs:~# echo 140 > /sys/class/gpio/export
root@cl-rootfs:~# echo out > /sys/class/gpio/gpio140/direction
root@cl-rootfs:~# echo 1 > /sys/class/gpio/gpio140/value

The above example assumes that the pinmux configuration of the corresponding pin is set to GPIO mode and the GPIO 140 is not requested in the Linux kernel.

IOT-GATE-iMX7 and SBC-IOT-iMX7: Linux: Debian

Contents

Overview

Using Debian Linux on SBC-IOT-iMX7

Connection and Logging In

Networking

Consoles

X Windows system

Software Management

Analog Audio

Analog Audio Playback

Audio Input Settings

Mic

Line In

Sample Audio Recording

WiFi

WiFi Initialization

wpa_supplicant

Bluetooth

Host Controller Interface (HCI) Initialization

MMC/SD

GPIO access

Example

See also

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