<div class="entry-content">
    <div class="jetpack-video-wrapper"><span class="embed-youtube" style="text-align:center; display: block;"><iframe src="https://www.youtube.com/embed/Lqc1jmbSxnE" class="youtube-player" width="740" height="416.418" frameborder="0" allowfullscreen></iframe></span>
    </div>
    <div class="blog-content">
Why is the thickness of PCB layers important? Explained.
    </div>
    
    <div class="blog-content-links">
        <div>
            Links:
        </div>
        <ul class="links-list">
            <li class="links-list-item"><a href="https://fedevel.com/courses">FEDEVEL Online courses</a></li>
        </ul>
    </div>  
</div>

How to choose PCB?

<div class="entry-content">
    <div class="jetpack-video-wrapper"><span class="embed-youtube" style="text-align:center; display: block;"><iframe src="https://www.youtube.com/embed/OG2Ci_xr0pM" class="youtube-player" width="740" height="416.418" frameborder="0" allowfullscreen></iframe></span>
    </div>
    <div class="blog-content">
If you would like to watch a full step-by-step tutorial about how to design your own custom keyboard, let me know in comments. Thx for watching.
    </div>


    <div class="blog-content-chapters">
        <div>
            Chapters:
        </div>
        <ul class="chapters-list">
            <li class="chapters-list-item"><span class="chapters-time">00:00</span><span class="chapters-text">Overview</span></li>
            <li class="chapters-list-item"><span class="chapters-time">00:20</span><span class="chapters-text">Keyboard parts</span></li>
            <li class="chapters-list-item"><span class="chapters-time">00:54</span><span class="chapters-text">Keyboard PCB design</span></li>
            <li class="chapters-list-item"><span class="chapters-time">02:35</span><span class="chapters-text">Small version</span></li>
            <li class="chapters-list-item"><span class="chapters-time">03:53</span><span class="chapters-text">Keyboard case</span></li>
            <li class="chapters-list-item"><span class="chapters-time">05:11</span><span class="chapters-text">Switches and encoders</span></li>
            <li class="chapters-list-item"><span class="chapters-time">06:10</span><span class="chapters-text">Keycaps</span></li>
            <li class="chapters-list-item"><span class="chapters-time">06:56</span><span class="chapters-text">Firmware QMK</span></li>
            <li class="chapters-list-item"><span class="chapters-time">07:52</span><span class="chapters-text">VIA app to set shortcuts</span></li>
            <li class="chapters-list-item"><span class="chapters-time">08:28</span><span class="chapters-text">Finished keyboard</span></li>
    </div>
    
    <div class="blog-content-links">
        <div>
            Links:
        </div>
        <ul class="links-list">
            <li class="links-list-item"><a href="https://fedevel.com/courses">FEDEVEL Online courses</a></li>
        </ul>
    </div>  
</div>

I Built This Custom Keyboard from Scratch

<div class="entry-content">
    <div class="jetpack-video-wrapper"><span class="embed-youtube" style="text-align:center; display: block;"><iframe src="https://www.youtube.com/embed/m3Ny3j5nH0U" class="youtube-player" width="740" height="416.418" frameborder="0" allowfullscreen></iframe></span>
    </div>
    <div class="blog-content">
Close look at BGA soldering, chip soldering, hand soldering and more
    </div>

    <div class="blog-content-chapters">
        <div>
            Chapters:
        </div>
        <ul class="chapters-list">
            <li class="chapters-list-item"><span class="chapters-time">00:00</span><span class="chapters-text">What is this video about</span></li>
            <li class="chapters-list-item"><span class="chapters-time">00:09</span><span class="chapters-text">Soldering BGA</span></li>
            <li class="chapters-list-item"><span class="chapters-time">01:18</span><span class="chapters-text">Soldering TSSOP</span></li>
            <li class="chapters-list-item"><span class="chapters-time">03:05</span><span class="chapters-text">Soldering QFN</span></li>
            <li class="chapters-list-item"><span class="chapters-time">06:02</span><span class="chapters-text">Hand soldering</span></li>
            <li class="chapters-list-item"><span class="chapters-time">08:35</span><span class="chapters-text">Multilayer PCB under a microscope</span></li>
    </div>

    
    <div class="blog-content-links">
        <div>
            Links:
        </div>
        <ul class="links-list">
            <li class="links-list-item"><a href="https://www.keyence.eu/yt-kib-vhx-0924">Microscope Keyence VHX-7000N</a></li>
            <li class="links-list-item"><a href="https://fedevel.com/courses">FEDEVEL Online courses</a></li>
        </ul>
    </div>  
</div>

Have you ever seen soldering THIS close?

<div class="entry-content">
    <div class="jetpack-video-wrapper"><span class="embed-youtube" style="text-align:center; display: block;"><iframe src="https://www.youtube.com/embed/LPeCKuz7tFs" class="youtube-player" width="740" height="416.418" frameborder="0" allowfullscreen></iframe></span>
    </div>
    <div class="blog-content">
        This is a real video, from bringing up <a href="http://www.imx6rex.com/">iMX6 Rex</a> board to Life.
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 1: Visual inspection</h2>
        What to look for:
        <ul class="content-list">
            <li class="content-list-item"><span class="content-text">if all the the components for your VARIANT are correctly fitted,</span></li>
            <li class="content-list-item"><span class="content-text">if all the pin 1 are placed correctly,</span></li>
            <li class="content-list-item"><span class="content-text">if there are no visible short circuits between pads,</span></li>
            <li class="content-list-item"><span class="content-text">if pads are soldered with a good quality (QFN pads, connectors with a small pitch… )</span></li>
        </ul><br>

        <i>Tip: Print out Assembly drawing with all the components and testpoints</i>
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 2: Measure impedance on power rails</h2>
        Go through all the power rails and measure impedance between 0R and a power rail. There must not be 0 OHM – that would be a short circuit.<br><br>

        <i>Tip: Some power rails may have very low impedance e.g. CPU core voltage, memories, …. 20OHMs, 40OHMs, 90OHMs … don’t be surprised.</i>
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 3: Connect power supply for the very first time</h2>
        <ul class="content-list">
            <li class="content-list-item"><span class="content-text">double check voltage output from your power supply (output level +5V, +12V, +24V, ….)</span></li>
            <li class="content-list-item"><span class="content-text">set your power supply current limit (always use power supply with limiting current e.g. 1A, 1.5A, …)</span></li>
            <li class="content-list-item"><span class="content-text">double check, if you have connected your board correctly (polarity + / -)</span></li>
            <li class="content-list-item"><span class="content-text">cover the board (in case something blow up e.g. if a capacitor is soldered the wrong way, it may very easily happen)</span></li>
            <li class="content-list-item"><span class="content-text">switch on the power</span></li>
            <li class="content-list-item"><span class="content-text">watch the maximum current, watch if current is changing or is stable (e.g. if it goes rappidly up, something may be wrong)</span></li>
            <li class="content-list-item"><span class="content-text">check component temperature with your finger (touch first all the integrated circuits, but try also passive components e.g. resistors, inductors and beads). Nothing should get very hot – if CPU goes very hot, use heatsink.</span></li>
        </ul><br>

        <i>Tip: Print out Assembly drawing with all the components and testpoints</i>
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 4: Measure all the on board voltages</h2>
        In this step check all the power rails.<br><br>

        <i>Tip: Many times, you set output voltage through a resistor divider, so it’s very important you know you didnt make any mistake in calculation and all to powers are in tollerance.</i>
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 5: Measure crystals and oscillators</h2>
        It’s very important you check all the crystals & oscillators. It may really happen, that some of the crystals may not start and board will not boot up.
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 6: Upload firmware</h2>
        We used Freescale MfgTool. If everything is working ok, after you connect your i.MX6 board to your PC (via USB), you will see a new USB device: HID-compliant device (USB input). Press “Start” to upload firmware into your board (you may want to check, what profile is used and what firmware will be uploaded). Watch the information about board current consumption. If everything goes ok, once the board starts booting, you will see the current fluctuation.
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 7: Check Serial TX signal</h2>
        Many times happen, that the RS232 cable that you use to connect your board with your PC is wrong (e.g. doesnt cross RX / TX signals correctly). It’s very good practise to measure TX activity directly on your CPU output. Connect an oscilloscope and when boards is booting, you will see some activity on the signal.
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 8: Connect Console</h2>
        This is the moment of the truth. If everything is ok, you will see console output co<br><br>

        <i>Tip: Very often, the default console settings are Baud rate: 115200 / Data: 8b / Parity: None / Stop: 1b / Flow control: None</i>
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Tip: Mark each board with a sticker and a number</h2>
        Use a sticker and write down board number, so you can easily identify the boards. Keep making notes about each board in a document or on a paper (e.g. if you see something unusual about the board – write it down, something doesn’t work – write it down, …).<br>
        Note: Some boards will come with a serial number sticker from production, so you don’t have to do this step.<br><br>

        For the very first testing, use the board which looks the best e.g. best soldered and everything looks ok.
    </div>
    
    <div class="blog-content-links">
        <div>
            Links:
        </div>
        <ul class="links-list">
            <li class="links-list-item"><a href="http://www.imx6rex.com/">iMX6 Rex</a></li>
        </ul>
    </div>  
</div>

8 Steps to Bring up your Board to Life

<div class="entry-content">
    <div class="blog-content">
        There are some differences between processors, but concept stays similar.
    </div>

    <div class="blog-content-img-wrapper">
        <img src="https://assets.fedevel.com/blog/2019/10/412af-how-arm-boots.png" alt="How ARM boots" />
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 1: Internal bootloader</h2>
        Based on bootstrap resistors (or/and eFuses) an internal bootloader (stored in CPU ROM) determines what peripheral will be used for booting (NAND, SD card, SATA, SPI, Ethernet, ….). From this peripheral a small code (bootloader) is downloaded to internal CPU SRAM and started.<br><br>

        <i>Tip: Often, the same internal bootloader can be used to download an image over serial port or USB and execute it. This is very useful during the initial stage of development (e.g. it’s possible to start a board with no firmware, booted it up and FLASH a firmware to the onboard memory).<br>

        Note: eFuses are used for some CPUs (e.g. Freescale processors). An eFuse defines some advanced boot settings (e.g. “boot from the SPI memory chip connected to SPI port 3 and chipselect 2”). Be aware, once an eFuse is programmed to 1, it can not be changed back to 0.</i>
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 2: Bootloader</h2>
        The main purpose of the Bootloader is initialize DRAM and the peripherals needed for OS booting. The OS files are then downloaded from a peripheral (NAND, SD card, SATA, SPI, Ethernet, ….) to DRAM and executed.<br><br>

        <i>Tip: Bootloader has some basic commands which can be used for debugging / testing (e.g. read / write memory, loading images to ram, starting images, …). Bootloader also keeps some parameters, which are later used to start OS (such: what serial port is used for OS output, memory size, file system info, video output info …..)</i>
    </div>

    <div class="blog-content">
        <h2 class="blog-content-heading">Step 3: OS</h2>
        At this stage, the OS is loaded and started.<br><br>

        <i>Note: There are differences between OS. Generally, Linux has two parts called Kernel and file system (Kernel is the OS itself, File System is the part where all the files are located).</i><br><br>

        Watch the practical demonstration in this 6 minutes video 
    </div>
    <div class="jetpack-video-wrapper"><span class="embed-youtube" style="text-align:center; display: block;"><iframe src="https://www.youtube.com/embed/TX3Ppe26emY" class="youtube-player" width="740" height="416.418" frameborder="0" allowfullscreen></iframe></span>
    </div>
</div>

How does ARM boot?

<div class="entry-content">
    <div class="jetpack-video-wrapper"><span class="embed-youtube" style="text-align:center; display: block;"><iframe src="https://www.youtube.com/embed/tyE4ruchZTM" class="youtube-player" width="740" height="416.418" frameborder="0" allowfullscreen></iframe></span>
    </div>
    <div class="blog-content">
        A big thank you to our assembly house AMSET for taking this video and building high quality boards. Enjoy this 1 minute video.
    </div>
    <div class="blog-content-links">
        <div>
            Links:
        </div>
        <ul class="links-list">
            <li class="links-list-item"><a href="https://amset.sk/">AMSET</a></li>
        </ul>
    </div> 
</div>


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