Ghost in the wire

Building a Root Filesystem The root filesystem is the fourth and the final element of embedded Linux. Once you have read this , you will be able build, boot, and run a simple embedded Linux system. The techniques I will describe here are broadly known as roll your own or RYO . Back in the earlier days of embedded Linux, this was the only way to create a root filesystem. There are still some use cases where an RYO root filesystem is applicable, for example, when the amount of RAM or storage is very limited, for quick demonstrations, or for any case in which your requirements are not (easily) covered by the standard build system tools. Nevertheless, these cases are quite rare. Let me emphasize that the purpose of this is educational; it is not meant to be a recipe for building everyday embedded systems: use the tools described in the next for this. The first objective is to create a minimal root filesystem that will give us a shell prompt. Then, using th...

Mastering Embedded Linux Programming: Selecting a Build System (5/16)

Selecting a Build System In the preceding's, we covered the four elements of embedded Linux and showed you step-by-step how to build a toolchain, a bootloader, a kernel, a root filesystem, and then combined them into a basic embedded Linux system. And there are a lot of steps! Now, it is time to look at ways to simplify the process by automating it as much as possible. I will look at how embedded build systems can help and look at two of them in particular: Buildroot and the Yocto Project. Both are complex and flexible tools, which would require an entire to describe fully how they work. In this , I only want to show you the general ideas behind build systems. I will show you how to build a simple device image to get an overall feel of the system, and then how to make some useful changes using the Nova board example from the previous s. In this , we will cover the following topics: Build systems Package formats and package managers Build...

Mastering Embedded Linux Programming : All About Bootloaders (2/16)

All About Bootloaders The bootloader is the second element of embedded Linux. It is the part that starts the system up and loads the operating system kernel. In this , I will look at the role of the bootloader and, in particular, how it passes control from itself to the kernel using a data structure called a device tree , also known as a flattened device tree or FDT . I will cover the basics of device trees, so that you will be able to follow the connections described in a device tree and relate it to real hardware. I will look at the popular open source bootloader, U-Boot, and show you how to use it to boot a target device, and also how to customize it to run on a new device, using the BeagleBone Black as an example. Finally, I will take a quick look at Barebox, a bootloader that shares its past with U-Boot, but which has, arguably, a cleaner design. In this , we will cover the following topics: What does a bootloader do? The boot sequence. Bootin...

List of 54 Hacks

#1 – Need to jot down something quickly? Open a temporary notepad in your browser by typing “data:text/html, <html contenteditable>” into the address bar. Remember to bookmark and rename it as Notepad. #2 - At website login pages, you can view masked passwords by changing the password input type as text. Most software and web developers probably know this. So, don’t leave your PC on! #3 - Test battery easily by dropping it few inches from the ground. A fully charged battery bounces very little, whereas a dead battery bounces around. Not really sure how to conduct the battery bounce test? Here’s a demo video. https://www.youtube.com/watch?v=nwfFBUVxpac . #4 - In Windows, create a new folder and name it “Control Panel Shortcuts.{ed7ba470-8e54-465e-825c-99712043e01c}”. Access any control settings in the folder. #5 - No description needed. #6 - Use wall hooks to attach iPad to the wall. #7 - Project Naptha...

How to make a Nintendo DS sized pocket computer (Raspberry Pi)

this is a little Nintendo DS sized computer using a Raspberry Pi and a bunch of off-the-shelf parts. It is a fully functional linux computer that can do most things a full system can (games, web stuff, videos, music etc). You can also output the video to an external monitor, transforming it into a desktop-ish computer. FEATURES Raspberry Pi 2 (900MHz CPU, 1GB RAM) 3x USB ports 1x Ethernet Fully QWERTY keyboard with backlight 3.5inch Touchscreen 1000mAh battery Clamshell case (made from 2x hard drive enclosures) Full Linux OS (Raspbian, using i3 window manager) Audio/Video out PARTS Raspberry Pi 2 Adafruit PiTFT Plus 3.5inch touchscreen 3x USB sockets 2x laptop hard drive cases Lots of thin wire 3.5mm 4 pole audio/video jack 1x low profile ethernet socket Adafruit Powerboost 1000c Mini wireless keyboard Power switch Tactile momentary switch 5v to 3.3v step down convertor 1000mah Lipo battery Piano Hinge Estimated Cost ~$120 TOOLS Soldering Iron Cutters Wire St...

A tutorial on how to get into an admin account on ANY computer.

Step 1: WARNING: I am NOT responsible for any expulsions or such if you do this at school/work! First, restart your computer. Step 2: Once you get to this screen, hold the power button on the computer until it turns off (no damage will be done, trust me). Step 3: If you did it correctly, you should get this screen. If you get something like "Windows did not shut down correctly," try again. Otherwise, select "Launch Startup Repair." Step 4: Let the repair go through. If you get this window, select "Cancel." Step 5: When you get this window, click on "Show problem details." Scroll down, and click the link on the very bottom. Notepad should pop up. Step 6: Go to File/Open, and double-click your "Local Disk" (Mine is D:/ because I have a virtual machine. Yours will probably be C:/). Step 7: Go to Windows/System32. Now do EXACTLY as I say, or you MIGHT break...

Mastering Embedded Linux Programming: Configuring and Building the Kernel (3/16)

Configuring and Building the Kernel The kernel is the third element of embedded Linux. It is the component that is responsible for managing resources and interfacing with hardware, and so affects almost every aspect of your final software build. It is usually tailored to your particular hardware configuration, although, as we saw in 2 , All About Bootloaders , device trees allow you to create a generic kernel that is tailored to particular hardware by the contents of the device tree. In this , we will look at how to get a kernel for a board, and how to configure and compile it. We will look again at bootstrap, this time focusing on the part the kernel plays. We will also look at device drivers and how they pick up information from the device tree. In this , we will cover the following topics: What does the kernel do? Choosing a kernel. Building the kernel. Booting the kernel. Porting Linux to a new board. What does the kernel do? Linu...

Linux Performance Tools

1) Linux Performance Tools: full version draft 2) I slightly redesigned the "Linux Performance Tools" chart - feedback wanted! 3) Linux performance monitoring tools

Mastering Embedded Linux Programming : Learning About Toolchains (1/16)

Learning About Toolchains The four elements of embedded Linux Every project begins by obtaining, customizing, and deploying these four elements: the toolchain, the bootloader, the kernel, and the root filesystem. This is the topic of the first section of this. Toolchain : The compiler and other tools needed to create code for your target device. Everything else depends on the toolchain. Bootloader : The program that initializes the board and loads the Linux kernel. Kernel : This is the heart of the system, managing system resources and interfacing with hardware. Root filesystem : Contains the libraries and programs that are run once the kernel has completed its initialization. Of course, there is also a fifth element, not mentioned here. That is the collection of programs specific to your embedded application which make the device do whatever it is supposed to do, be it weigh groceries, display movies, control a robot, or fly a drone. Typi...

How to identify Calculator is Programmable or Non-Programmable Calculator ?

Some competitive examinations allow the candidates for the use of a calculator but may permit to use the only calculator of non-programmable type. Calculators that are NOT programmable: This is what a non-programmable calculator looks like. List of non-programmable calculators of some famous brands like Casio , Sharp , Texas Instruments , Hewlett-Packard . Calculators that are programmable: Programmable calculators can automatically carry out a sequence of operations under control of a stored program, much like a computer. Examples of programmable calculators are shown in the picture. This calculator runs on a Computer Algebra System (CAS). A CAS helps to make certain complicated algebraic functions automatic and less tedious. As you can see, these calculators also have graphing capabilities. A calculator with graphing capabilities is most likely to be programmable. The easy way to tell if the calculator has graphing c...

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