健忘的工程師筆記本

 UVC 裝置會有個video node, 哪一個可用? 用 v4l2-ctl 可以看出 device caps 不同 struct v4l2_capability cam_cap; ioctl(fd, VIDIOC_QUERYCAP, &cam_cap); videodev2.h /* Values for 'capabilities' field */ #define V4L2_CAP_VIDEO_CAPTURE 0x00000001  /* Is a video capture device */ #define V4L2_CAP_META_CAPTURE 0x00800000  /* Is a metadata capture device */ PS:  VIDIOC_QUERYCAP 要確認的是 device_caps 而不是 capabilities   reference:  https://askubuntu.com/questions/1294041/why-only-one-usb-camera-shows-two-video4linux-devices https://bugzilla.kernel.org/show_bug.cgi?id=199575

echo 0 > /sys/bus/usb/devices/usb1/authorized echo 1 > /sys/bus/usb/devices/usb1/authorized

1.   沒有現成的可以一鍵同步的方法。 2.   最方便的是用 GitHub Desktop ，請看下面圖示 點選 merge 在 fetch 3.   另一種就是用 command line. # git remote -v # git remote add upstream git@GIT.AVER.COM:EDU/FW/m10v/linux.git # git fetch upstream # git checkout S510-2 # git merge upstream/S510-2 # git push origin S510-2 --tags   若 upstream 上有新的 branch # git checkout upstream/S510-3 # git checkout -b  S510-3 # git push origin S510-3 --tags PS: 加上 --tags 才會將 tag 也一併同步   Reference: https://docs.github.com/en/free-pro-team@latest/github/collaborating-with-issues-and-pull-requests/syncing-a-fork https://www.peterdavehello.org/2014/02/update_forked_repository/ https://gitbook.tw/chapters/github/syncing-a-fork.html  

reference: https://linuxize.com/post/how-to-install-xrdp-on-ubuntu-20-04/ 我的 ubuntu 是 desktop 版本，所以不用安裝桌面套件 sudo apt install xrdp sudo adduser xrdp ssl-cert sudo systemctl restart xrdp sudo systemctl status xrdp 這樣就可以用 windows 遠端桌面開啟

The CONFIG_ROOT_NFS configuration option, which depends on CONFIG_IP_PNP. To enable root filesystem over NFS you must enable the "IP: kernel level autoconfiguration" option in the "Networking options" menu first.

將uboot bootargs 設成下面組合就可以 bootargs rootdelay=5 root=/dev/nfs rw nfsroot=$(serverip):$(rootpath),nolock,vers=4,tcp ip=dhcp nfsrootdebug bootargs rootdelay=5 root=/dev/nfs rw nfsroot=$(serverip):$(rootpath) ip=dhcp nfsrootdebug bootargs rootdelay=5 root=/dev/nfs nfsroot=$(serverip):$(rootpath),nolock,vers=4,tcp rw ip=$(ipaddr):$(serverip):0.0.0.0:255.255.255.0::eth0:off nfsrootdebug # nfsrootdebug --> 連線不成功, 可以debug # vers=4,tcp --> 連線不成功, 確認一下 server 的版本。nfsstat –s <<- Print server-side statistics                             新版 ubuntu 應該都是 v3/v4 了.

stty -F /dev/ttyS1 stty -F /dev/ttyS1 raw -echo -echoe -echok stty -F /dev/ttyS1 115200 stty -F /dev/ttyS1 speed stty -F /dev/ttyS2 stty -F /dev/ttyS2 raw -echo -echoe -echok stty -F /dev/ttyS2 115200 stty -F /dev/ttyS2 speed Statistics # cat /proc/tty/driver/<driver_name> reference: http://www.armadeus.org/wiki/index.php?title=Serial_ports_usage_on_Linux

How to create a defconfig file from a .config? # make savedefconfig # cp defconfig arch/arm/configs/my_cool_defconfig

# sudo -i # sudo su - 這樣就可以取得 root 的權限做事了

DisplaySwitch.exe /clone  -> will duplicate displays. DisplaySwitch.exe /extend -> will extend displays. Also you can use Win+P if you want a quick shortcut.

./scripts/dtc/dtc -I dtb -O dts -o devicetree.dts devicetree.dtb $ sudo apt-get install device-tree-compiler $ dtc -I dtb -O dts juno.dtb > juno.dts $ dtc -I dts -O dtb juno.dts > juno.dtb   reference: https://forum.digilentinc.com/topic/2427-how-to-decompile-dtb-file/ Device Tree, reference: Device Tree（一）：背景介绍  http://www.wowotech.net/device_model/why-dt.html Device Tree（二）：基本概念  http://www.wowotech.net/device_model/dt_basic_concept.html Device Tree（三）：代码分析  http://www.wowotech.net/device_model/dt-code-analysis.html Device Tree（四）：文件结构解析 http://www.wowotech.net/device_model/dt-code-file-struct-parse.html x

reference:  https://ownyourbits.com/2017/09/13/copy-with-a-progress-bar-with-cpv/

Better Linux Disk Caching & Performance with vm.dirty_ratio & vm.dirty_background_ratio reference :          https://feichashao.com/dirty_ratio_and_dirty_background_ratio/         https://lonesysadmin.net/2013/12/22/better-linux-disk-caching-performance-vm-dirty_ratio/

error: The following untracked working tree files would be overwritten by checkout: Remove all untracked files: git clean  -d  -fx . -x means ignored files are also removed as well as files unknown to git. -d means remove untracked directories in addition to untracked files. -f is required to force it to run. reference: https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-clean.html https://stackoverflow.com/questions/17404316/the-following-untracked-working-tree-files-would-be-overwritten-by-merge-but-i/35067275

Makefile的賦值運算符(=, :=, +=, ?=) 總結: = 是最基本的賦值 := 會覆蓋變數之前的值 ?= 變數為空時才給值，不然則維持之前的值 += 將值附加到變數的後面 另外 =, :=這兩賦值運算符號在網路上查詢，常常會看到這種說法: = 在執行時擴展(values within it are recursively expanded when the variable is used, not when it's declared) := 在定義時擴展(values within it are expanded at declaration time) 而白話一點的說法如下範例所示   1. =   make會將整個makefile展開後，才決定變數的值。也就是说，變數的值會是整個Makefile中最後被指定的值。看例子： x = hello y = $(x) world! x = hi all: @echo $(y)   在上例中，輸出結果將會是 hi world! ，而不是 hello world!   2. :=   變數的值在Makefile展開途中就會被給定，而不是整個Makefile展開後的最终值。 x := hello y := $(x) world! x := hi all: @echo $(y)   輸出結果 ====> hello world!

當開啟一個 Excel工作表，進入後要看工作表上的公式如何運作，才發現工作表受到密碼保護，上網搜尋了一下破解方法，試過很多種方法都太麻煩，最後終於找到最簡單的破解方法，借此分享，希望用的到的人不必再一一去試。 Excel 工作表密碼保護的解除方法 利用 VBA 巨集程式破解法： 1：打開該文件，切換到“檢視”選項，點擊“巨集”→“錄製巨集”，出現“錄製巨集”窗口，在“巨集名稱”隨意輸入一名稱(假設：ABC)，點擊“確定”退出； 2：再點擊“巨集”→“檢視巨集”，選擇“巨集名稱”下的“ABC”並點擊右邊的“編輯”，會自動打開“Microsoft Visual Basic”編輯器，用以下的內容完全替換右側窗口中的所有編碼： Sub  ABC( )    Dim i As Integer, j As Integer, k As Integer    Dim l As Integer, m As Integer, n As Integer    Dim i1 As Integer, i2 As Integer, i3 As Integer    Dim i4 As Integer, i5 As Integer, i6 As Integer    On Error Resume Next    For i = 65 To 66: For j = 65 To 66: For k = 65 To 66       For l = 65 To 66: For m = 65 To 66: For i1 = 65 To 66          For i2 = 65 To 66: For i3 = 65 To 66: For i4 = 65 To 66             For i5 = 65 To 66: For i6 = 65 To 66: For n = 32 To 126             ...

USB 相關     先記錄，再研究 1. USB Host 簡介     http://pollos-blog.blogspot.tw/2015/08/usb-host.html 2. USB Video Class 簡介     http://pollos-blog.blogspot.tw/2014/10/usb-video-class.html 3. USB PTP/MTP 簡介     http://pollos-blog.blogspot.tw/2014/10/usb-ptpmtp.html 4. RS232 over USB 簡介     http://pollos-blog.blogspot.tw/2014/10/rs232-over-usb.html 5. USB Mass Storage Class 簡介     http://pollos-blog.blogspot.tw/2014/10/usb-mass-storage-class.html 6. USB 簡介     USB 簡介[1]    http://pollos-blog.blogspot.tw/2014/07/usb-1.html     USB 簡介[2]    http://pollos-blog.blogspot.tw/2014/07/usb-2.html     USB 簡介[3]    http://pollos-blog.blogspot.tw/2014/07/usb-3.html     USB 簡介[4]    http://pollos-blog.blogspot.tw/2014/07/usb-4.html     USB 簡介[5]    http://pollos-blog.blogspot.tw/2014/07/usb-5.html     USB...

tar cf - /folder-with-big-files -P | pv -s $(du -sb /folder-with-big-files | awk '{print $1}') | gzip > big-files.tar.gz 4.69GB 0:04:50 [16.3MB/s] [==========================> ] 78% ETA 0:01:21 $ pv big-files.tar.gz | tar xjf - -C target_directory reference:         http://www.tecmint.com/monitor-copy-backup-tar-progress-in-linux-using-pv-command/

distcc is a tool for speeding up compilation of source code by using distributed computing over a computer network. 此工具就是可以把編譯進行分散式的處理，相當方便快速。 利用 3 台 pc 實現 distcc ... 1. 先安裝好 apt-get install distcc 2. 在每台 pc 時，開啟 distcc daemon server     # distccd --daemon --allow 127.0.0.1 --allow 10.100.90.0/24 3.   time make -j10 CC="distcc arm-arago-linux-gnueabi-gcc" CROSS_COMPILE=arm-arago-linux-gnueabi- ARCH=arm uImage real 1m48.143s user 5m55.716s sys 0m12.236s  export DISTCC_HOSTS="localhost 10.100.90.232 10.100.90.240"  time make -j10 CC="distcc arm-arago-linux-gnueabi-gcc" CROSS_COMPILE=arm-arago-linux-gnueabi- ARCH=arm uImage real 1m4.804s user 2m45.832s sys 0m8.844s  export DISTCC_HOSTS="--randomize localhost 10.100.90.232 10.100.90.240,cpp,lzo"  time distcc-pump make -j16 CC="distcc arm-arago-linux-gnueabi-gcc" CROSS_COMPILE=arm-arago-linux-gnueabi- ARCH=arm uImage real 0m59.147s user 2...

2738, Could not access VBScript run time for custom action. 2739, Could not access JScript run time for custom action. VBScript 1. regedit，刪除機碼 "HKCU\SOFTWARE\Classes\Wow6432Node\CLSID\{B54F3741-5B07-11CF-A4B0-00AA004A55E8}" 2. 用Administrator的身份啟動命令提示字元，然後執行以下指令： 64-bit version of Windows: cd c:\windows\syswow64 regsvr32 vbscript.dll 32-bit version of Windows: cd c:\windows\system32 regsvr32 vbscript.dll JScript 1. regedit，刪除機碼 "HKCU\SOFTWARE\Classes\Wow6432Node\CLSID\{F414C260-6AC0-11CF-B6D1-00AA00BBBB58}" 2. 用Administrator的身份啟動命令提示字元，然後執行以下指令： 64-bit version of Windows: cd c:\windows\syswow64 regsvr32 jscript.dll 32-bit version of Windows: cd c:\windows\system32 regsvr32 jscript.dll referencd: https://tw.answers.yahoo.com/question/index?qid=20100713110248AAGkno2   https://blogs.msdn.microsoft.com/heaths/2007/05/31/windows-installer-errors-2738-and-2739-with-script-custom-actions/   http://boyilee.blogspot.tw...