Category Archives: projects

3D Printing a Tool to find your Veins

I find that the best projects start with a purpose, however what most people don’t tell you is that the purpose doesn’t always have to be prophetic, necessary or groundbreaking. For a lot of people starting a project can be as simple as the intention:

“I want to blink an LED”

When I joined Leeds Hackspace this was the first concept I was introduced to, along with the Arduino platform. This small and, to me, humble beginning has led me down a path which resulted in a change of job, an introduction into an entirely new community and a world of Technological interest and learning that has took me from an interest in computing and network programming to electronics, 3D printing, scanning and more.

My recent project started with a purpose, (if you’re squeamish you may want to clench, skip a sentence or look away) when you visit the doctor for a blood test and they struggle to find a vein, usually there’s one nurse that can manage it. You don’t expect to be told:

“Usually when it’s this difficult, we would go in via your neck, but we can’t justify it for this test”

To say that’s horrifying is an understatement, so the response that came naturally was obvious to me. I must find a solution to this problem. How on earth can I make my veins easier to find so that I can prevent this in future?

Almost coincidentally, in some occurrence reminiscent of the telephone or television being invented at the same time in two sides of the world, I found my solution quickly. After exhausting the thoughts of ultrasound, radiation or other forms of potentially lethal solutions I happened upon an instructables.

3D printing is only as simple and easy as the tool that you’re using, and I quickly discovered that the printer at Leeds Hackspace required some tweaking. Those who’re familiar with their own built 3D printer will be no stranger to this concept. After a number of nights tinkering with the settings and observing the temperatures, the ‘hot end’ required cooling and the heat bed required heating. I feel that I’ve written stranger sentences.

Finally, the basis of the device is completed. However, now I have to populate it with components! Well, a few online searches and ordering later and I would have the crux of the job. LEDs of the correct wavelength to be able to be absorbed by non-oxygenated blood but reflected by the rest of my skin. Soon, I’ll be able to see my own veins.

 

The hardest part, I soon discovered, was that this portable design for a vein finder was not designed with an internal layout in mind. After a few rather hand-warming shorts later I managed to acquire suitable heat-shrink and seal up the device appropriately. Yes, it runs on two double-A batteries at 1.5volts (rechargeables don’t quite have the voltage/current for a setup like this, but that could be adjusted).

In the space of, consolidated, a week, I have something to take to the doctors with me the next time I visit. Thanks to the wavelength (628nm) of the red LEDs it’s difficult to capture on a digital camera, but hopefully, they won’t be going at me via the neck.

Here are some bonus pictures of the finished product in action:

Running Debian on the Atmel SAMA5D3 Board

So when I wanted to build a version of Linux for the SAMA5D3 board that wasn’t Yocto or a demonstration image, then I started to struggle to find solutions.

Then I happened upon Robert Nelson’s guide on EEWiki. However, I found that it was not as straightforward as I had hoped. A few instructions were confusing and out of order with one another.

Here I present the steps I took to have Debian working on the SAMA5D3, some are the same, others are importantly different. I also have a .IMG of the SD Card I created available.

I set this up using a laptop with Debian Linux installed; I imagine it doesn’t matter which version of Linux you have; you could probably use Cygwin on windows.

You will need:

  • An SD card (I tend to work with at least a Class 6, 8gByte)
  • An Atmel SAMA5D3 board
  • A computer with Linux (unless you’re able to translate the steps to Windows, feel free) with an internet connection
  • A Serial debug cable

    • Open up a terminal, create a directory to work in and run the following commands to grab Linaro, the ARM cross compiler:

    wget -c https://releases.linaro.org/14.03/components/toolchain/binaries/gcc-linaro-arm-linux-gnueabihf-4.8-2014.03_linux.tar.xz
    tar xf gcc-linaro-arm-linux-gnueabihf-4.8-2014.03_linux.tar.xz
    export CC=`pwd`/gcc-linaro-arm-linux-gnueabihf-4.8-2014.03_linux/bin/arm-linux-gnueabihf-

    Then test the version of gcc:

    ${CC}gcc --version

    Which should output something like this:

    arm-linux-gnueabihf-gcc (crosstool-NG linaro-1.13.1-4.8-2014.03 - Linaro GCC 2014.03) 4.8.3 20140303 (prerelease)
    Copyright (C) 2013 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions. There is NO
    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

    Now we need to grab U-Boot and patch it for the SAMA5D3, you will need to have GIT installed on your distribution of Linux:

    git clone git://git.denx.de/u-boot.git
    cd u-boot/
    git checkout v2014.04 -b tmp
    wget -c https://raw.github.com/eewiki/u-boot-patches/master/v2014.04/0001-sama5d3_xplained-uEnv.txt-bootz-n-fixes.patch
    patch -p1 < 0001-sama5d3_xplained-uEnv.txt-bootz-n-fixes.patch make ARCH=arm CROSS_COMPILE=${CC} distclean make ARCH=arm CROSS_COMPILE=${CC} sama5d3_xplained_mmc_config make ARCH=arm CROSS_COMPILE=${CC}
    Now time to build a kernel for the board!

    git clone https://github.com/RobertCNelson/armv7_devel.git
    cd armv7_devel/

    As of the time of writing the current mainline kernel was v3.14:

    git checkout origin/v3.14.x-sama5-armv7 -b tmp
    ./build_kernel.sh

    After the kernel has compiled, you’re presented with a menu config screen where you can include or build additional modules. For example, you can incorporate GSPCA webcam support.

    Now, we want to acquire the root system files for Debian, which are handily available:

    wget -c https://rcn-ee.net/deb/minfs/wheezy/debian-7.4-minimal-armhf-2014-04-01.tar.xz
    tar x -f debian-7.4-minimal-armhf-2014-04-01.tar.xz

    Then insert your SDCard, either using a USB SDCard reader or one on your computer if you have one. I had to use a USB SDCard reader. In Linux we can type “dmesg” at a terminal to give us the /dev/ information for the device we’ve plugged in (for example mine’s /dev/sdb), in the following examples, we use mmcblk0, so just replace it for your relevant device id.

    In the following steps we will erase the SDCard and set it up with the relevant partitions:

    export DISK=/dev/mmcblk0
    sudo dd if=/dev/zero of=${DISK} bs=1M count=16

    sudo sfdisk --in-order --Linux --unit M ${DISK} < <-__EOF__ 1,48,0xE,* ,,,- __EOF__
    If the linux system you're using identifies the device as something similar to mmcblk0 then to format and mount, execute:

    sudo mkfs.vfat -F 16 ${DISK}p1 -n boot
    sudo mkfs.ext4 ${DISK}p2 -L rootfs

    sudo mkdir -p /media/boot/
    sudo mkdir -p /media/rootfs/

    sudo mount ${DISK}p1 /media/boot/
    sudo mount ${DISK}p2 /media/rootfs/

    Else if the device identifies itself as something similar to sdb then to format and mount, execute:

    sudo mkfs.vfat -F 16 ${DISK}1 -n boot
    sudo mkfs.ext4 ${DISK}2 -L rootfs

    sudo mkdir -p /media/boot/
    sudo mkdir -p /media/rootfs/

    sudo mount ${DISK}1 /media/boot/
    sudo mount ${DISK}2 /media/rootfs/

    Note: You may not need to mount the partitions as new(ish/er) distributions tend to automatically mount partitions upon detection/insertion/creation.

    Create a text file using your editor of choice (for the record I prefer vi …) called uEnv.txt and put in it the following, the sama board uses the ‘mmc’ naming convention:

    optargs=quiet init=/lib/systemd/systemd
    console=ttyS0,115200
    mmcroot=/dev/mmcblk0p2 ro
    mmcrootfstype=ext4 rootwait fixrtc

    Now we’ll extract and copy across all of the necessary files, the locations should all be relative to the initial directory we’ve been working in and you created, they should all be executed as root/sudo:

    sudo cp -v ./u-boot/spl/u-boot-spl.bin /media/boot/BOOT.BIN
    sudo cp -v ./u-boot/u-boot.img /media/boot/

    sudo cp -v ./uEnv.txt /media/boot/

    sudo tar -xvp --same-owner --numeric-owner -f ./debian-0.4-minimal-armhf-2014-04-01/armhf-rootfs-debian-wheezy.tar -C /media/rootfs

    sudo cp -v ./armv7_devel/deploy/3.14.0-sama5-armv7-r9.zImage /media/boot/zImage

    sudo mkdir -p /media/boot/dtbs/
    sudo tar xvo -f 3.14.0-sama5-armv7-r9-dtbs.tar.gz -C /media/boot/dtbs

    sudo tar xv -f 3.14.0-sama5-armv7-r9-modules.tar.gz -C /media/rootfs

    And to setup the partition mounting (if you don’t like vi, replace with nano, emacs or whatever your preferred editor is):

    sudo vi /media/rootfs/etc/fstab

    Insert into it (in vi, press ‘i’ on your keyboard, then type it in, or copy/paste it into your terminal window):

    /dev/mmcblk0p2 / auto errors=remount-ro 0 1
    /dev/mmcblk0p1 /boot/uboot auto defaults 0 2

    Close and save the file (in vi, press ESC then type in :x and hit enter, which saves and quits).

    Then setup the network interfaces:

    sudo vi /media/rootfs/etc/network/interfaces

    With the following at the end of the file (you can use your cursor keys to navigate vi until you get to where you want to insert):

    allow-hotplug eth0
    iface eth0 inet dhcp

    allow-hotplug eth1
    iface eth1 inet dhcp

    And setup our serial line:

    sudo vi /media/rootfs/etc/inittab

    With the following at the end of the file:

    T0:23:respawn:/sbin/getty -L ttyS0 115200 vt102

    Now we want to unmount our SD Card, so close down any windows/open files that’re on the card and run the following from a terminal:

    sync
    sudo umount /media/boot
    sudo umount /media/rootfs

    Our SD Card should be setup! The only thing to do now, is remove the jumper at JP5 on the SAMA5D3 to ensure it’ll boot from the SD Card, connect a serial cable to the debug header J23 so we can see what it’s doing, with the settings in minicom/Putty/your terminal editor of choice:

    Baud: 115200
    Data Bits: 8
    Stop Bits: 1
    Parity: None
    Flow Control: None

    Then connect the USB cable to power the board, then press the reset button for good measure and watch it boot up!

    Login details:


    User: root
    Pass: root

    User: debian
    Pass: temppwd

    When I created this image from scratch initially I encountered a number of problems. The main part is that the SD Card needs to be setup as root, with the files copied over as root. This is because of the permission level required to read the SD Card when the SAMA5D3 board loads up.

    The other problem I encountered was the settings for uEnv were confusing me on the eewiki guide.

    Something that might trip up anyone following this guide word for word in future is if the kernel version increases, this will need to be altered in the filenames in the guide above. Failing that, the SD Card img I have prepared should help:

    Debian-SAMA5D3-140409.zip (543mB)
    Debian-SAMA5D3-140409.md5 (211b)

    OpenWRT on an MR3020 – ish

    I bought a portable 9000mAh battery pack – which gives out 5 to 5.5v at 2200 mA. Why? Well the intention here is to power something which doesn’t take much, well, to power, for a very long time. This is where the MR3020 steps in.

    By default its intention as a device is to share, over 2.4Ghz WiFi (I think, I’m not sure if it does 5Ghz, I haven’t checked, but it does do 802.11bgn) a 3g or 3.5g mobile connection (from USB). It can also share this over your standard LAN Ethernet, or it can share the Ethernet over the WiFi.. I think you get the idea?

    Well there’s this firmware called OpenWRT which lets me do what I want with it, effectively turning it into a small, linux-esque computer with its Atheros processor at the core.

    So my intention is to plug in a GPS adapter, USB storage pen-drive, configure the device over Ethernet and use that 9000mAh battery pack to power it. I didn’t mention? The MR3020 is powered by a mini-usb port. Wonderful.

    However, this project hasn’t been without, shall we say, trouble. You see, when you flash a firmware (its Operating System, like Windows or Linux) to the device it is then restricted to those files and programs in that firmware (short of some configuration files) and to expand upon it further you need to to install them. This can be done through ‘opkg’ which is OpenWRT’s package manager.

    Unfortunately you’ve just used up the majority of the space on the device flashing the firmware, so if you’re fortunate you can add the packages to allow you to use a USB storage pendrive. If not, it’s time to make your own tasty good make feel nice firmware.

    Which is what I tried to do. This did not go well. This is because the core of the firmware, at the base of it all is the kernel which interfaces between the software and the hardware. I had foolishly filled it with too much and it couldn’t load it. I had effectively ‘bricked‘ my mini router. That is to say, it no longer functioned as it should and it was stuck in a loop, rebooting.

    A bit of soldering, the assistance of Nav from the Leeds Hackspace lending me a serial cable later, I was back on track with a working device. What I had to do, was transfer a new firmware to the device, using only the bootloader and TFTP (over Ethernet). This worked, to a point that I could now get into the failsafe mode of OpenWRT rather than just the bootloader. Where I then, more easily, transferred a better, larger, firmware to it and ensured that the configurations were reset to default.

    Now I’m going to try building a firmware again, or maybe I’ll find one suitable and upgrade it. I had looked at PirateBox but that was mainly for sharing files, and MiniPwner – but the problems encountered with that (MiniPwner) are (by default) its kernel is out of date for the latest packages (easily fixed, I found, by using an upgrade firmware from OpenWRT) and a bit more tinkering to get it just right.

    So back to trying to get the USB pen-drive and GPS to work at the same time (hacking in a USB hub) along with relocating the packages to the USB pen-drive.

    Then, hopefully, I can do what I planned to. Triangulate and map WiFi access points on a Google Maps style layout referenced to GPS layout. Or something similar, maybe I’ll introduce BlueTooth or anything else I can pick up with a sensor. Yes, I might just be able to attach in a Minimus32.