Difference between revisions of "IoTGateway/Features/Linux/Peripheral"

Revision as of 03:22, 6 December 2017 (view source) Tim.liang (talk | contribs) ← Older edit		Revision as of 03:24, 6 December 2017 (view source) Tim.liang (talk | contribs) Newer edit →
Line 722:		Line 722:
	*::[[File:SPI boot up to verify.png|800px|SPI boot up to verify.png]]		*::[[File:SPI boot up to verify.png|800px|SPI boot up to verify.png]]
	*:write some special data for u-boot test		*:write some special data for u-boot test
−	<div style="margin-left: 5em;">	+	<div style="margin-left: 5em;"><syntaxhighlight lang="bash">
−
−	<syntaxhighlight lang="bash">
	$ echo "This is a mtd1." | dd of=/dev/mtdblock1 bs=1 seek=0 2>/dev/null		$ echo "This is a mtd1." | dd of=/dev/mtdblock1 bs=1 seek=0 2>/dev/null
	$ echo "This is a mtd2." | dd of=/dev/mtdblock2 bs=1 seek=0 2>/dev/null		$ echo "This is a mtd2." | dd of=/dev/mtdblock2 bs=1 seek=0 2>/dev/null
	$ dd if=/dev/mtdblock1 bs=1 count=32 2>/dev/null | hexdump -C		$ dd if=/dev/mtdblock1 bs=1 count=32 2>/dev/null | hexdump -C
	$ dd if=/dev/mtdblock2 bs=1 count=32 2>/dev/null | hexdump -C		$ dd if=/dev/mtdblock2 bs=1 count=32 2>/dev/null | hexdump -C
−	</syntaxhighlight>[[File:SPI write data for u-boot test.png|600px|SPI write data for u-boot test.png]] </div>	+	</syntaxhighlight>[[File:SPI write data for u-boot test.png|600px|SPI write data for u-boot test.png]]</div>
	*u-boot		*u-boot
	*:patch u-boot by [[Media:u-boot-2009.08_spi5_w25q64.patch|u-boot-2009.08_spi5_w25q64.patch]]		*:patch u-boot by [[Media:u-boot-2009.08_spi5_w25q64.patch|u-boot-2009.08_spi5_w25q64.patch]]
	*:rebuild the u-boot image		*:rebuild the u-boot image
	*:practical test		*:practical test
−	<div style="margin-left: 5em;">	+	<div style="margin-left: 5em;"><syntaxhighlight lang="bash">
−
−	<syntaxhighlight lang="bash">
	> sf probe 4:0; sf read 0x10800000 0 10; md.b 0x10800000 10		> sf probe 4:0; sf read 0x10800000 0 10; md.b 0x10800000 10
	> sf probe 4:1; sf read 0x10800000 0 10; md.b 0x10800000 10		> sf probe 4:1; sf read 0x10800000 0 10; md.b 0x10800000 10
−	</syntaxhighlight>[[File:SPI u-boot verify.png|600px|SPI u-boot verify.png]] </div>	+	</syntaxhighlight>[[File:SPI u-boot verify.png|600px|SPI u-boot verify.png]]</div>
	== SPWG/JEDIA ==		== SPWG/JEDIA ==
Line 884:		Line 880:
−	== LED ==	+
		+	== Led ==

---

Revision as of 03:24, 6 December 2017

ADC

System that converts an analog signal into a digital signal.

ROM-5420

ROM-5420 support ADC read-out through the battery driver

#  cat /sys/class/power_supply/battery/uevent
POWER_SUPPLY_NAME=battery
POWER_SUPPLY_STATUS=Charging
POWER_SUPPLY_HEALTH=Good
POWER_SUPPLY_PRESENT=1
POWER_SUPPLY_TECHNOLOGY=Li-ion
POWER_SUPPLY_CYCLE_COUNT=-1472729340
POWER_SUPPLY_VOLTAGE_NOW=8340
POWER_SUPPLY_CURRENT_NOW=648
POWER_SUPPLY_CAPACITY=96
POWER_SUPPLY_TEMP=25
POWER_SUPPLY_TIME_TO_EMPTY_AVG=0
POWER_SUPPLY_TIME_TO_FULL_AVG=0
POWER_SUPPLY_SERIAL_NUMBER=0000
POWER_SUPPLY_VOLTAGE_MAX_DESIGN=0
POWER_SUPPLY_ENERGY_NOW=149457984
POWER_SUPPLY_ENERGY_FULL=149457984
POWER_SUPPLY_ENERGY_FULL_DESIGN=149457984
POWER_SUPPLY_CHARGE_NOW=-1472729340
POWER_SUPPLY_CHARGE_FULL=-1472729340
POWER_SUPPLY_CHARGE_FULL_DESIGN=-1472729340

Audio

Sound Card

# cat /proc/asound/cards
0 [sgtl5000       ]: sgtl5000 - sgtl5000
                     sgtl5000
1 [imxspdif       ]: imx-spdif - imx-spdif
                     imx-spdif
2 [imxhdmisoc     ]: imx-hdmi-soc - imx-hdmi-soc
                     imx-hdmi-soc

Record

Record wav file for 5 secs

# arecord -t wav -c 1 -r 44100 -d 5 test.wav

Playback

Playback

# aplay test.wav

Playback on another sound card

# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: sgtl5000 [sgtl5000], device 0: HiFi sgtl5000-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: imxspdif [imx-spdif], device 0: S/PDIF PCM snd-soc-dummy-dai-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: imxhdmisoc [imx-hdmi-soc], device 0: i.MX HDMI Audio Tx hdmi-hifi-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0

Playback on SPDIF　（card 1，Subdevice 0)

# aplay -D plughw:1,0 Advantech.wav

Playback on HDMI　（card 2，Subdevice 0)

# aplay -D plughw:2,0 Advantech.wav

Backlight

The relevant files

/sys/class/graphics/fb0
/sys/devices/platform/mxc_sdc_fb.1/graphics/fb0
/sys/devices/platform/mxc_sdc_fb.1/graphics/fb0/power
/sys/devices/platform/mxc_sdc_fb.1
/sys/class/graphics
/sys/class/backlight
/sys/class/backlight/pwm-backlight.0

Turn off

echo 1 > /sys/class/backlight/pwm-backlight.0/bl_power

Turn on

echo 0 > /sys/class/backlight/pwm-backlight.0/bl_power

Brightness control

echo 0 > /sys/class/backlight/pwm-backlight.0/brightness
echo 255 > /sys/class/backlight/pwm-backlight.0/brightness

Camera

Test

Preview

# gst-launch-1.0 imxv4l2src device=/dev/video0 ! 'video/x-raw,format=NV12,width=1920,height=1080,framerate=30/1' ! imxv4l2sink

Capture

# gst-launch-1.0 imxv4l2src num-buffers=1 !  jpegenc ! filesink location=test.jpeg

View

# VSALPHA=1 gst-launch-1.0 filesrc location=test.jpeg ! jpegdec ! imagefreeze ! imxv4l2sink

Record

# gst-launch-1.0 imxv4l2src device=/dev/video0 num-buffers=300 ! 'video/x-raw,format=NV12,width=1920,height=1080,framerate=30/1' ! queue ! vpuenc_h264 ! matroskamux ! filesink location=output.avi

Play Video

# gst-launch-1.0 playbin uri=file:////home/root/output.avi

CAN Bus

Configuration/Test

Configuration

• Connect can0 and can1

<CAN1_D+> connect to <CAN2_D+>

<CAN1_D-> connect to <CAN2_D->

# ip link set can0 up type can bitrate 125000
# ip link set can1 up type can bitrate 125000

Test

• Test 1

# candump can1 &
# cansend can0 12345678#123412341234

The following shows the result

can1  12345678   [6]  12 34 12 34 12 34

• Test 2

# cansend can0 133#ababdede

The following shows the result

can1       133   [4]  AB AB DE DE

CPU

CPU Frequency

Using available CPU frequency policies

Read CPU frequency

# cpufreq-info  | grep "current CPU frequency"
current CPU frequency is 396 MHz (asserted by call to hardware).
current CPU frequency is 396 MHz (asserted by call to hardware).
current CPU frequency is 396 MHz (asserted by call to hardware).
current CPU frequency is 396 MHz (asserted by call to hardware).

Check available CPU frequency policy

# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors
conservative ondemand userspace powersave interactive performance

Change CPU frequency policy

# echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

Check CPU frequency

# cpufreq-info  | grep "current CPU frequency"
current CPU frequency is 996 MHz (asserted by call to hardware).
current CPU frequency is 996 MHz (asserted by call to hardware).
current CPU frequency is 996 MHz (asserted by call to hardware).
current CPU frequency is 996 MHz (asserted by call to hardware).

Setting the CPU frequency explicitly

Read available CPU frequenies

# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
396000 792000 996000

Change CPU frequency explicitly

# echo userspace > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
# echo 792000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

Check CPU frequency

# cpufreq-info  | grep "current CPU frequency"
current CPU frequency is 792 MHz (asserted by call to hardware).
current CPU frequency is 792 MHz (asserted by call to hardware).
current CPU frequency is 792 MHz (asserted by call to hardware).
current CPU frequency is 792 MHz (asserted by call to hardware).

CPU Hot-Plugging

Manually turn off CPU cores

#echo 0 >  /sys/devices/system/cpu/cpu1/online
CPU1: shutdown

• Can't turn off cpu0

Check CPU is turned off

#cat /proc/interrupts | head -n 1 
 CPU0       CPU2       CPU3

Ethernet

Ethernet Speed

Depend on connect device

#ethtool eth0 | grep -i speed
Speed: 100Mb/s

iPerf

iPerf user guide

host

Host ip is 192.168.0.2
#iperf -s

target

#iperf -c 192.168.0.2 -w 100M -t 60 -i 10
------------------------------------------------------------
Client connecting to 192.168.0.2, TCP port 5001
TCP window size:  320 KByte (WARNING: requested  100 MByte)
------------------------------------------------------------
[  3] local 192.168.0.1 port 35389 connected with 192.168.0.2 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec   560 MBytes   470 Mbits/sec
[  3] 10.0-20.0 sec   554 MBytes   465 Mbits/sec
[  3] 20.0-30.0 sec   537 MBytes   450 Mbits/sec
[  3] 30.0-40.0 sec   553 MBytes   464 Mbits/sec
[  3] 40.0-50.0 sec   557 MBytes   468 Mbits/sec
[  3] 50.0-60.0 sec   542 MBytes   455 Mbits/sec
[  3]  0.0-60.0 sec  3.23 GBytes   462 Mbits/sec

Framebuffer

The frame buffer device provides an abstraction for the graphics hardware. It represents the frame buffer of some video hardware and allows application software to access the graphics hardware through a well-defined interface, so the software doesn't need to know anything about the low-level (hardware register) stuff.

The device is accessed through special device nodes, usually located in the /dev directory, i.e. /dev/fb*.

Get Display Mode

Refer to link as below:

How to get Display mode

Get framebuffer device

i.MX series

# cat /sys/class/graphics/fb*/fsl_disp_dev_property
hdmi
overlay
lcd
overlay
ldb

Test

Playing different videos on different displays

i.MX series

Modify display device parameters

i.MX 6Q/D

• /usr/share/imx_6q_display_config

i.MX 6 Solo

• /usr/share/imx_6sx_display_config

The following is an example of the display configuration for dual display mode, HDMI(master) + LCD(slave)+ LVDS(slave).

[hdmi]
device = /dev/video17
fmt = RGBP
width = 1920
height = 1080
[lcd]
device = /dev/video18
fmt = RGBP
width = 1920
height = 1080
[ldb]
device = /dev/video20
fmt = RGBP
width = 800
height = 480
alpha = 0

Play video on HDMI

# gst-launch-1.0  playbin uri=file:////tools/Advantech.avi

Play video on HDMI+VGA

# gst-launch-1.0  playbin uri=file:////tools/Advantech.avi video-sink="overlaysink display-lcd=true"

Play video on HDMI+VGA+LVDS

# gst-launch-1.0  playbin uri=file:////tools/Advantech.avi video-sink="overlaysink display-lcd=true display-ldb=true"

GPIO

Configuration/Test

Configuration

Export GPIO then you can use control GPIO from userr space through sysfs

GPIO 27 is taken as an example:

Export GPIO 27

# echo 27 > /sys/class/gpio/export

Set GPIO direction to in/out .   Note: gpio27 will be export to gpio1 

# echo "in" > /sys/class/gpio/gpio27/direction

Set GPIO value 0/1 if GPIO pin define is output

#  echo 1 > /sys/class/gpio/gpio27/value

Directly force a GPIO to output and set its initial value(high=1 low=0) 

# echo high > /sys/class/gpio/gpio27/direction

Used as IRQ signal

Note:You have to configure GPIO to input

#  echo "rising" > /sys/class/gpio/gpio27/edge

• rising: Trigger on rising edge
• falling: Trigger on falling edge
• both: Trigger on both edges
• none: Disable interrupt on both edges

Unexport GPIO 27

# echo 27 > /sys/class/gpio/unexport

Test

GPIO 27 and GPIO 29 are taken as an example:

• Connect GPIO 27 and GPIO 29
• Export GPIO 27 and GPIO 29

# echo 27 > /sys/class/gpio/export
# echo 29 > /sys/class/gpio/export

• Set GPIO 27 to output

# echo "out" > /sys/class/gpio/gpio27/direction

• Set GPIO 29 to input

# echo "in" > /sys/class/gpio/gpio29/direction

• Change GPIO 27 to 1 and read GPIO 29 value

# echo 1 > /sys/class/gpio/gpio27/value
# cat /sys/class/gpio/gpio29/value
1

• Change GPIO 27 to 0 and read GPIO 29 value

# echo 0 > /sys/class/gpio/gpio27/value
# cat /sys/class/gpio/gpio29/value
0

GPS

GPS module ublox 5

• linux kernel config

Device Drivers --->

[*] USB support --->

<*> USB Modem (CDC ACM) support

[*] USB Gadget Support

[m] USB Gadget Drivers

[*] USB support --->

[*] Support for Freescale on-chip EHCI USB controller

<*> USB Serial Converter support --->

[*] USB Generic Serial Driver

• list usb device

  no device

  

  device plugged in

  

• testing

  

I2C

Test

Check i2c busses

• Usage: i2cdetect [-y] [-a] [-q|-r] I2CBUS [FIRST LAST]

#i2cdetect -l
i2c-0   i2c             21a0000.i2c                             I2C adapter
i2c-1   i2c             21a4000.i2c                             I2C adapter
i2c-2   i2c             21a8000.i2c                             I2C adapter

Check devices on i2c-2 bus

#i2cdetect -y -r 2
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: UU UU -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- UU --

Dump I2C device register content

• Usage: i2cdump [-f] [-y] [-r first-last] I2CBUS ADDRESS [MODE [BANK [BANKREG]]]

# i2cdump -y -f 2 0x76
No size specified (using byte-data access)
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f    0123456789abcdef
00: 54 00 80 43 40 40 40 00 00 00 00 00 00 00 ff ff    T.?C@@@S........
10: 85 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ?...............
20: 00 00 00 18 ff ff ff ff ff ff ff ff ff ff ff ff    ...?............
30: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
40: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
50: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
60: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
70: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
80: 54 00 80 43 40 40 40 53 00 00 00 00 00 00 ff ff    T.?C@@@S........
90: 85 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ?...............
a0: 00 00 00 18 ff ff ff ff ff ff ff ff ff ff ff ff    ...?............
b0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
c0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
d0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
e0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................

Read a single byte

• Usage: i2cget [-f] [-y] I2CBUS CHIP-ADDRESS [DATA-ADDRESS [MODE]]

# i2cget -f -y 2 0x76 7
0x00

Change its value and verify it

• Usage: i2cset [-f] [-y] [-m MASK] [-r] I2CBUS CHIP-ADDRESS DATA-ADDRESS [VALUE] ... [MODE]

# i2cset -f -y 2 0x76 7 0x53
# i2cget -f -y 2 0x76 7
0x53

IR

To decode the infrared signals and provide an uniform interface

lircd -d /dev/lirc0

used parameters:

-d --device=device    read from given device
-u --uinput           generate Linux input events

Executes commands on an IR signal decoded by lircd,

irexec -d /devlirc0

Note: if show these message after running lircd

lircd: can't open or create /var/run/lirc/lircd.pid
lircd: No such file or directory

It has to add the "/var/run/lirc" folder

mkdir /var/run/lirc

How to debug:

1. To check that signals are decoded correctly

mode2 -d /dev/lirc0

It repeats to show "space" and "pulse" while clicking a control button

space 8451531
pulse 476

2. To check input events.

First, It must add the parameter,"-u", in lircd command

lircd -d /dev/lirc0 -u

It will register at inputX,

input: lircd as /devices/virtual/input/input1 

Run evtest to check events

evtest -d /dev/input/event1

One Wire

Example

RTC

Test

Confirm Which RTC

rtc-s35390a is taken as an example:

# dmesg| grep rtc0
[    1.644600] rtc-s35390a 0-0030: rtc core: registered rtc-s35390a as rtc0

rtc-s35390a is rtc0

Set system time to current, then write to RTC

# date 021710452016 && hwclock -w && date
Wed Feb 17 10:45:00 UTC 2016
Wed Feb 17 10:45:00 UTC 2016

Set one incorrect time, then read time from RTC to verify

# date 010100002000 && hwclock -r && date
Sat Jan  1 00:00:00 UTC 2000
Wed Feb 17 10:45:32 2016  0.000000 seconds
Sat Jan  1 00:00:00 UTC 2000

Restore the RTC time to system time

# hwclock -s && date
Wed Feb 17 10:46:26 UTC 2016

SATA

SATA speed

Check SATA speed

# dmesg| grep "SATA link up"
[    1.983660] ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300)

Change SATA speed

• Add 'libata.force=1.5Gbps' to kernel boot arguments in U-boot

#setenv sataargs $sataargs libata.force=1.5Gbps

Verify

# dmesg| grep "SATA link up"
[    1.993678] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 310)

Test

Insert SATA disk before boot

#find /sys/ . -name block | grep ata | xargs ls $1
sda

• According to the above content, we can know sda is our SATA disk

Generate random file

# dd if=/dev/urandom of=data bs=1 count=1024

Back up

# dd if=/dev/sda of=backup bs=1 count=1024 skip=4096

Write to SATA disk

# dd if=data of=/dev/sda bs=1 seek=4096

Read and Verify

# dd if=/dev/sda of=data1 bs=1 count=1024 skip=4096
# diff data data1

If fail, it shows as below:

Binary files data1 and data differ

Restore

# dd if=backup of=/dev/sda bs=1 seek=4096

SD/MMC

Test

Check sysfs node

# cat /sys/block/mmcblk0/device/type
MMC
# cat /sys/block/mmcblk1/device/type
SD

SD Card is taken as an example:

Generate random file

# dd if=/dev/urandom of=data bs=1 count=1024

Back up

# dd if=/dev/mmcblk1 of=backup bs=1 count=1024 skip=4096

Write to SD

# dd if=data of=/dev/mmcblk1 bs=1 seek=4096

Read and Verify

# dd if=/dev/mmcblk1 of=data1 bs=1 count=1024 skip=4096
# diff data data1

If fail, it shows as below:

Binary files data1 and data differ

Restore

# dd if=backup of=/dev/mmcblk1 bs=1 seek=4096

SPI

The "Serial Peripheral Interface" (SPI) is a synchronous four wire serial link used to connect microcontrollers to sensors, memory, and peripherals.

Test

spi flash(m25p80 is taken as an example:

Generate random file

# dd if=/dev/urandom of=data bs=1 count=1024

Back up

# dd if=/dev/mtdblock1 of=backup bs=1 count=1024 skip=$((0xD3000))

Write to mtdblock1

# dd if=data of=/dev/mtdblock1 bs=1 seek=$((0xD3000))

Read and Verify

# dd if=/dev/mtdblock1 of=data1 bs=1 count=1024 skip=$((0xD3000))
# diff data data1

If fail, it shows as below:

Binary files data1 and data differ

Restore

# dd if=backup of=/dev/mtdblock1 bs=1 seek=$((0xD3000))

How to recognize W25Q64FV

The following operations demonstrate how to customize 7420LBV2330 to recognize the two W25Q64FVs on customized carrier board with ROM-7420 connected.

• linux kernel

  add the following line to /arch/arm/configs/imx6_rom7420_defconfig

  CONFIG_SPI_IMX_ECSPI5_1=y

  

  rebuild the kernel image

  $ ./cfg_kernel.sh imx6_rom7420_defconfig

  $ ./mk_kernel.sh

  boot up to verify

  

  write some special data for u-boot test

• u-boot

  patch u-boot by u-boot-2009.08_spi5_w25q64.patch

  rebuild the u-boot image

  practical test

SPWG/JEDIA

Standard Panels Working Group (SPWG)

Japan Electronic Industry Development Association (JEIDA)

How to setting SPWG/JEIDA mode in RISC?

Modify Register GPR(IOMUXC_GPR2)value

Address : 0x020E0008(h)

BIT6 and BIT8 set "0" (SPWG)

BIT6 and BIT8 set "1" (JEIDA)

UART

RS-232

Configuration

Connect UART1(ttymxc1) TX and RX

Use stty command to set baudrate

# stty -F /dev/ttymxc1 115200

Test

Check baudrate

# stty -F /dev/ttymxc1 115200
speed 115200 baud; line = 0;

Read

#cat /dev/ttymxc1 &

Send

#echo test > /dev/ttymxc1 
test

USB

Host

Test

Insert a USB disk

usb 1-1.2: new high-speed USB device number 4 using ci_hdrc
usb-storage 1-1.2:1.0: USB Mass Storage device detected
scsi2 : usb-storage 1-1.2:1.0
scsi 2:0:0:0: Direct-Access     Generic- SD/MMC           1.00 PQ: 0 ANSI: 0 CCS
sd 2:0:0:0: [sda] 3862528 512-byte logical blocks: (1.97 GB/1.84 GiB)
sd 2:0:0:0: [sda] Write Protect is off
sd 2:0:0:0: [sda] No Caching mode page found
sd 2:0:0:0: [sda] Assuming drive cache: write through
sd 2:0:0:0: [sda] No Caching mode page found
sd 2:0:0:0: [sda] Assuming drive cache: write through
sda: sda1
sd 2:0:0:0: [sda] No Caching mode page found
sd 2:0:0:0: [sda] Assuming drive cache: write through
sd 2:0:0:0: [sda] Attached SCSI removable disk

• According to the above content, we can know sda is our usb disk

Generate random file

# dd if=/dev/urandom of=data bs=1 count=1024

Back up

# dd if=/dev/sda of=backup bs=1 count=1024 skip=4096

Write to usb disk

# dd if=data of=/dev/sda bs=1 seek=4096

Read and Verify

# dd if=/dev/sda of=data1 bs=1 count=1024 skip=4096
# diff data data1

If fail, it shows as below:

Binary files data1 and data differ

Restore

# dd if=backup of=/dev/sda bs=1 seek=4096

Client

Test

Watchdog

Instroduction

Introduction:

A Watchdog Timer (WDT) is a hardware circuit that can reset the computer system in case of a software fault.

Watchdog API

You can refer to the path as below in kernel source code to write a simple program to test watchdog

Documentation/watchdog/watchdog-api.txt

Example

i.MX series

NXP has written a tool to test watchdog in /unit_tests/

1.Executing wdt_driver_test.out

#/unit_tests/wdt_driver_test.out
Usage: wdt_driver_test <timeout> <sleep> <test>
timeout: value in seconds to cause wdt timeout/reset
sleep: value in seconds to service the wdt
test: 0 - Service wdt with ioctl(), 1 - with write()

2.Please try below command to set timeout as 10 seconds, system will reboot after then.

#/unit_tests/wdt_driver_test.out 10 5 0
Starting wdt_driver (timeout: 10, sleep: 5, test: ioctl)
Trying to set timeout value=10 seconds
The actual timeout was set to 10 seconds
Now reading back -- The timeout is 10 seconds
Press [CTRL+C] then you should be able to see below result:

3.Press "ctrl+c"

imx2-wdt imx2-wdt.0: Unexpected close: Expect reboot!
Then system will reboot in 10 second

Led