IOT-GATE-iMX7 and SBC-IOT-iMX7: Linux: Debian
Contents
- 1 Overview
- 2 Using Debian Linux on SBC-IOT-iMX7
- 3 See also
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 stretch. 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 stretch Linux image includes more than 400 software packages. Among them:
- Core system
- Debian package management system
- X11 Windowing System
- Xfce 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.
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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 the Xfce window manager.
By default, Xfce is initiated automatically during startup. Xfce can be initiated manually by typing startx.
USB mouse and keyboard should be connected for interaction with X Windows.
Use the following credentials to login to the Xfce window manager:
User: compulab Password: compulab
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
IOT-GATE-iMX7 and SBC-IOT-iMX7 provides an analog audio interface, which is registered as a standard ALSA sound card. 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 ...
Bluez5 & PulseAudio
Debian stretch/sid is using BlueZ 5 and PluseAudio 5, which are fairly new.
BlueZ 5 dropped support for alsa, so the solution for now is to use PulseAudio.
PulseAudio 5 only supports the A2DP profile and not HSP/HFP.
- Software to install pulseaudio, pulseaudio-module-bluetooth
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debian-image.tar.bz2 has all these packages pre-installed. Continue to the Start PulseAudio section if you use this root filesystem. |
Install and configure PulseAudio
root@cl-rootfs:~# apt-get install --no-install-recommends pulseaudio pulseaudio-module-bluetooth
- Create a systemd service for running pulseaudio as the pulse user.
root@cl-rootfs:~# cat << eof > /etc/systemd/system/pulseaudio.service [Unit] Description=Pulse Audio [Service] Type=simple ExecStart=/usr/bin/pulseaudio --system --disallow-exit --disable-shm [Install] WantedBy=multi-user.target eof root@cl-rootfs:~# chown pulse:pulse /etc/systemd/system/pulseaudio.service
- Create a dbus configuration file for running pulseaudio. Give the pulse user permission to use Bluetooth.
root@cl-rootfs:~# cat << eof > /etc/dbus-1/system.d/pulseaudio-bluetooth.conf
<busconfig>
<policy user="pulse">
<allow send_destination="org.bluez"/>
</policy>
</busconfig>
eof
root@cl-rootfs:~# chmod 0666 /etc/dbus-1/system.d/pulseaudio-bluetooth.conf
- Paste the following lines to the end of /etc/pulse/system.pa:
root@cl-rootfs:~# cat << eof >> /etc/pulse/system.pa ### Automatically load driver modules for Bluetooth hardware .ifexists module-bluetooth-policy.so load-module module-bluetooth-policy .endif .ifexists module-bluetooth-discover.so load-module module-bluetooth-discover .endif eof
- Create /var/run/pulse/.config/pulse directory. Change its ownership.
root@cl-rootfs:~# mkdir -p /var/run/pulse/.config/pulse root@cl-rootfs:~# chown -R pulse:pulse /var/run/pulse
- Make the root belong to the pulse-access,audio groups
root@cl-rootfs:~# usermod -a -G pulse-access,audio root
Start PulseAudio
- Start PulseAudio service
root@cl-rootfs:~# systemctl daemon-reload root@cl-rootfs:~# systemctl start pulseaudio.service
- Make sure that the service is active, running and reports on no errors.
root@cl-rootfs:~# systemctl status pulseaudio.service
Loaded: loaded (/etc/systemd/system/pulseaudio.service; disabled)
Active: active (running) since Mon 2015-07-20 12:00:13 UTC; 1min 34s ago
Main PID: 805 (pulseaudio)
CGroup: /system.slice/pulseaudio.service
└─805 /usr/bin/pulseaudio --system --disallow-exit --disable-shm
Bluez5 pairing
PulseAudio 5.x supports A2DP per default.
Make sure the following packages are installed:
pulseaudio pulseaudio-module-bluetooth pulseaudio-utils, bluez, bluez-tools.
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Without pulseaudio-module-bluetooth you won't be able to connect after the next pairing and you won't get any usable error messages. |
- Start the Bluetooth system:
root@cl-rootfs:~# systemctl start bluetooth
Now we can use the bluetoothctl command line utility to pair and connect. Run
root@cl-rootfs:~# bluetoothctl [bluetooth]#
to be greeted by its internal command prompt.Then enter:
[bluetooth]# power on [bluetooth]# agent on [bluetooth]# default-agent [bluetooth]# scan on
Now make sure that your headset is in pairing mode. It should be discovered shortly. For example,
[NEW] Device 00:07:A4:F2:B3:CB Motorola HT820
shows a device that calls itself "Motorola HT820" and has MAC address 00:07:A4:F2:B3:CB. We will now use that MAC address to initiate the pairing:
[bluetooth]# pair 00:07:A4:F2:B3:CB
After pairing, you also need to explicitly connect the device:
[bluetooth]# connect 00:07:A4:F2:B3:CB
If everything works correctly, you now have a separate output device in PulseAudio.
You can now disable scanning again and exit the program:
[bluetooth]# scan off [bluetooth]# exit
Playback using PulseAudio
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Next examples assume that the device mac address is 00_07_A4_F2_B3_CB |
- Show the PulseAudio device
root@cl-rootfs:~# pactl list cards | awk '/00_07_A4_F2_B3_CB/' RS=""
Card #1
Name: bluez_card.00_07_A4_F2_B3_CB
Driver: module-bluez5-device.c
Owner Module: 13
Properties:
device.description = "Motorola HT820"
device.string = "00:07:A4:F2:B3:CB"
device.api = "bluez"
device.class = "sound"
device.bus = "bluetooth"
device.form_factor = "headset"
bluez.path = "/org/bluez/hci0/dev_00_07_A4_F2_B3_CB"
bluez.class = "0x240404"
bluez.alias = "Motorola HT820"
device.icon_name = "audio-headset-bluetooth"
device.intended_roles = "phone"
Profiles:
headset_head_unit: Headset Head Unit (HSP/HFP) (sinks: 1, sources: 1, priority: 20, available: no)
a2dp_sink: High Fidelity Playback (A2DP Sink) (sinks: 1, sources: 0, priority: 10, available: yes)
off: Off (sinks: 0, sources: 0, priority: 0, available: yes)
Active Profile: a2dp_sink
Ports:
headset-output: Headset (priority: 0, latency offset: 0 usec)
Part of profile(s): headset_head_unit, a2dp_sink
headset-input: Headset (priority: 0, latency offset: 0 usec, not available)
Part of profile(s): headset_head_unit
- Make sure the active card profile is a2dp_sink. Otherwise switch to it:
# pactl set-card-profile 1 a2dp_sink
- Show the PulseAudio sink
root@cl-rootfs:~# pactl list sinks | awk '/00_07_A4_F2_B3_CB/' RS=""
Sink #2
State: SUSPENDED
Name: bluez_sink.00_07_A4_F2_B3_CB.a2dp_sink
Description: Motorola HT820
Driver: module-bluez5-device.c
Sample Specification: s16le 2ch 48000Hz
Channel Map: front-left,front-right
Owner Module: 13
Mute: no
Volume: front-left: 65536 / 100% / 0.00 dB, front-right: 65536 / 100% / 0.00 dB
balance 0.00
Base Volume: 65536 / 100% / 0.00 dB
Monitor Source: bluez_sink.00_07_A4_F2_B3_CB.a2dp_sink.monitor
Latency: 0 usec, configured 0 usec
Flags: HARDWARE DECIBEL_VOLUME LATENCY
Properties:
bluetooth.protocol = "a2dp_sink"
device.description = "Motorola HT820"
device.string = "00:07:A4:F2:B3:CB"
device.api = "bluez"
device.class = "sound"
device.bus = "bluetooth"
device.form_factor = "headset"
bluez.path = "/org/bluez/hci0/dev_00_07_A4_F2_B3_CB"
bluez.class = "0x240404"
bluez.alias = "Motorola HT820"
device.icon_name = "audio-headset-bluetooth"
device.intended_roles = "phone"
Ports:
headset-output: Headset (priority: 0)
Active Port: headset-output
Formats:
pcm
- Play sound using paplay. Example:
root@cl-rootfs:~# paplay -d bluez_sink.00_07_A4_F2_B3_CB.a2dp_sink /path/to/<audio-file.wav>
Controller–area network (CAN)
IOT-GATE-iMX7 and SBC-IOT-iMX7 assembled with Y configuration option feature a Flexible Controller Area Network (FLEXCAN) interface. The FLEXCAN implements full CAN protocol version 2.0B and supports both the standard and the extended frame format as well as a programmable data bit rate up to 1Mbit/s.
CAN interface is routed to RJ11 connector P9. Connector pin-out is described in section 5.11 of the IOT-GATE-IMX7 reference guide.
Device tree blob
Using CAN bus interface requires a dedicated device-tree blob.
The following U-Boot command should be used to select the appropriate device tree blob:
CL-SOM-iMX7 # setenv fdtfile imx7d-sbc-iot-imx7-can.dtb CL-SOM-iMX7 # saveenv
Software installation
- Use the following command to install can-utils:
root@cl-rootfs:~# apt-get install --no-install-recommends can-utils
Loading CAN modules
If the FLEXCAN driver and/or Raw CAN protocol compiled as module(s), they must be loaded prior to enabling CAN interface.
- The FLEXCAN driver gets loaded automatically. Make sure it is loaded:
root@cl-rootfs:~# lsmod | grep can flexcan 102 0
- The FLEXCAN driver can be loaded manually:
root@cl-rootfs:~# modprobe flexcan 30a00000.can supply xceiver not found, using dummy regulator flexcan 30a00000.can: device registered (reg_base=f5a00000, irq=277) 30a10000.can supply xceiver not found, using dummy regulator flexcan 30a10000.can: device registered (reg_base=f5a10000, irq=278)
- Load Raw CAN protocol module:
root@cl-rootfs:~# modprobe can-raw can: raw protocol (rev 20120528)
CAN interface configuration
It is recommended configure the CAN interface, with the iproute2 utilities.
- To make sure the right ip utility is used, run:
root@cl-rootfs:~# ip -V ip utility, iproute2-ss151103
- Configure the CAN interface bit-rate to 125 Kbits/sec (values of up to 1Mbit/sec are supported):
root@cl-rootfs:~# ip link set can0 type can bitrate 125000
- Enable the CAN interface:
root@cl-rootfs:~# ip link set can0 up flexcan 30a00000.can can0: writing ctrl=0x0b312005
Send/Receive packets
Use cansend and candump utilities to send and receive packets via CAN interface.
- Send standard CAN frame (on the first device):
root@cl-rootfs:~# cansend can0 111#1122334455667788
- Send extended CAN frame (on the first device):
root@cl-rootfs:~# cansend can0 11111111#1122334455667788
- Dump all received data frames as well as error frames (on the second device):
root@cl-rootfs:~# candump any,0:0,#FFFFFFFF can0 111 [8] 11 22 33 44 55 66 77 88 can0 11111111 [8] 11 22 33 44 55 66 77 88
4G/3G Cellular Modem
Both IOT-GATE-iMX7 Internet of Things Gateway and SBC-IOT-iMX7 Internet of Things Single Board Computer are equipped with on-board micro-SIM card socket and support cellular communication using 4G/3G cellular modem with USB interface in mini-PCIe form-factor. Following 3G cellular modules have been tested:
- Telit HE910-D 3G modem
- SIMcom SIM5360 3G modem
- SIMcom SIM7100E 4G modem
In order to use 4G/3G cellular modem the several software packages have to be installed.
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debian-image.tar.bz2 has all these packages pre-installed. Continue to the Loading kernel modules section if you use this root filesystem. |
Installing Debian packages
root@cm-debian:~# apt-get install libpcap0.8 libuniconf4.6 libwvstreams4.6-base libwvstreams4.6-extras ppp wvdial
Loading kernel modules
Device driver modules require no user interaction and get loaded automatically. If for some reason device driver modules are not loaded automatically, please load them manually:
- USB Driver for GSM modems and Qualcomm MSM Interface (QMI) WWAN driver are required for SIMcom modules:
root@cl-som-imx7-sid:~# modprobe option root@cl-som-imx7-sid:~# modprobe qmi_wwan
- USB Abstract Control Model driver is required for Telit HE910-D:
root@cl-som-imx7-sid:~# modprobe cdc-acm
Point-to-Point protocol (PPP) drivers must be loaded manually prior to dialing:
root@cl-som-imx7-sid:~# modprobe ppp_generic root@cl-som-imx7-sid:~# modprobe ppp_async root@cl-som-imx7-sid:~# modprobe ppp_synctty root@cl-som-imx7-sid:~# modprobe bsd_comp root@cl-som-imx7-sid:~# modprobe ppp_deflate
WvDial
WvDial is a Point-to-Point Protocol dialer that automatically detects modem, and can log into almost any Internet Service Provider without a complicated configuration. First, edit the wldial configuration file. Please use the a correct ISP APN instead of YOUR_ISP_APN stub:
root@cl-som-imx7-sid:~# cat /etc/wvdial.conf [Dialer cellular] # Your modem device. Usually /dev/ttyUSB0 or /dev/ttyACM0 #Modem = /dev/ttyACM0 Modem = /dev/ttyUSB3 # Port speeds that're worth testing: # 921600 # 460800 # 115200 # 57600 Baud = 115200 # If your SIM card has a PIN, comment this line, uncomment the next one, and # change the PIN shown to your PIN. Init = ATZ # Init = ATZ+CPIN="0000" # If you know your ISP's APN, specify it instead of YOUR_ISP_APN below. # If you don't, you may be able to find out on the 'net, or from tech # support. # # There's also an APN table at https://wiki.ubuntu.com/NetworkManager/Hardware/3G . # # If you can't find it, you might be able to dial out without setting an APN # (especially from a mobile phone). Just comment this line and uncomment # the next one. Init2 = AT+CGDCONT=1,"IP","YOUR_ISP_APN" #Init2 = AT+CGDCONT=1,"IP" # Most services/devices dial with *99# . A few seem to require *99***1# Phone = *99# # These often suffice, but your ISP might require different details. They're # often dummy details used for all users on the ISP, frequently the ISP's # name, but some ISP's do require you to use a real username and password. Username = dummy Password = dummy
The following command can be used for dialing:
root@cm-debian:~# wvdial cellular &
RS485
IOT-GATE-iMX7 and SBC-IOT-iMX7 assembled without the Y configuration option feature a half-duplex RS485 port with a data bit rate of up to 12Mbit/s.
The RS485 interface is routed to RJ11 connector P9. Connector pin-out is described in section 5.11 of the IOT-GATE-IMX7 reference guide.
Device tree blob
Using the RS485 interface requires a dedicated device-tree blob.
The following U-Boot command should be used to select the appropriate device tree blob:
CL-SOM-iMX7 # setenv fdtfile imx7d-sbc-iot-imx7-rs485-hdx.dtb CL-SOM-iMX7 # saveenv
Example
Serial terminal emulator application can be used to test the RS485 port.
- Use the following commands to install the Minicom application (terminal emulator):
root@cl-debian:~# apt-get update root@cl-debian:~# apt-get -y install minicom
- Use the following command to start Minicom with the user space device of the RS485 (/dev/ttymxc6).
root@cl-debian:~# minicom -D /dev/ttymxc6
- Follow the following steps to disable hardware flow control
- Open the menu "Configure Minicom" with CTRL-a followed by the letter 'o'.
- Select "Serial port setup"
- Press the letter 'f'.
- Press the Esc key twice.
- The characters that are typed in the terminal are transmitted to the RS485 port.
- The characters that are received from the RS485 port are displayed in the terminal.
- Press CTRL-a followed by the letter 'x' to exit from Minicom
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
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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. |
