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My random notes about the stuff I've done

Tag Archives: Embedded Linux

Pleco Phase01 completed

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I started playing with microcontrollers in 2005 and, if not at the very start, at least very quickly I decided to aim to have some sort of remote controlled Linux device with controllable camera with digital wireless communication. Now, 6 years later, I have completed my first phase :)

Couple of photos of the earlier devices are shown in the project page.

After several planning iterations and code rewrites I ended up using Qt both on the remote controlled Gumstix and on the GUI controller. I decided that trying to optimize everything from the memory and CPU consumption to the network bandwidth just isn’t worth the time spent in implementing it. The most CPU intensive task is the video encoding to H263 and that’s done in the DSP. I’m running MeeGo on the Gumstix and it provides e.g. the GStreamer plugins for the DSP.

Using Qt framework with self made simple protocol over UDP I got the Phase01 code implemented quite quickly compared to my previous efforts. The protocol allows low priority packets (like periodic statistics and video stream) to be lost and guarantees the passing of high priority packets (control commands etc.). Also only the latest control command of each type is retransmitted, i.e. an old packet is not retransmitted if a new overriding command has already been given.

The controller GUI shows the states the slave sends, like motor speeds, WLAN signal strength, CPU load average and some protocol statistics like round trip time and the number of retransmissions.

Currently the motors are controlled using the a,s,d,w keys in 10% steps and the camera is controlled dragging the mouse left button pressed on top of the video window.

Here’s a video (direct link) of the Phase01. You need HTML5 video capable browser with Ogg Theora/Vorbis codecs.

Filed under MeeGo, Projects, gumstix
Apr 5, 2011

ALIP on n8x0

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ARM and Movial announced a second stable release of ARM Linux Internet Platform (ALIP) generic repository. ALIP got other updates as well, see a blog post about them in Movial’s Sandbox or the actual release notes.

The Kaze project for n8x0 devices was updated to use the generic-2 branch as well. There are no built images provided, but ALIP is relatively easy to compile if one is already familiar with Scratchbox. The ALIP rootfs works with the Maemo kernel and initfs and it can be booted nicely from an MMC/SD card, so no need to destroy the Maemo from the device just to test ALIP.


Kaze on n8x0

ALIP requires newer SB components (and specific toolchains) but the newer SB components should work just fine with Maemo targets and Maemo toolchains. Or the newer SB can be installed in a different directory from tarballs and used concurrently with the Maemo SB.

Follow the From scratch instructions but replace alip-project with kaze-project and don’t pass the -cbeagleboard. You should pass -c multimedia to include 3rd party provided (by me actually) gst-ffmpeg to the build.

If you want to include WebKit engine and Midori UI to it, add “midori” to the components file.

Unfortunately the X driver for OMAPs (xf86-video-omapfb) in the stable branch in omap-repository has a bug concerning n8x0 devices and you should use master branch of it if you want to test video playback. The easiest way to switch using master branch for this component is to clone the n8x0 configuration repository and switch the branch before running the matrix install.


git clone git://linux.onarm.com/git/n8x0/config/n8x0.git
vi n8x0/suite/n8x0-recommended
# Add the branch: Component("xf86-video-omapfb", branch="master")
matrix install -c multimedia

After the install you should include the binary DSP tasks from the device (they are proprietary and cannot be distributed). Use the helper script (get_nokia_binaries.sh) in src/platform-n8x0 that fetches them from the device over ssh and reinstall the component before creating the rootfs image:


matrix install-only -c multimedia platform-n8x0

Lots of things are still broken:

  • Power button tries to suspend, which fails and does nothing.
  • WLAN encryption keys are not stored succesfully.
  • WPA doesn’t work (WEP and unencrypted do work).
  • Midori should be started after networking.
  • There’s no ssh client (but dbclient as it’s dropbear).
  • Power management.
  • Default XFCE theme doesn’t look cool.
  • Etc.

But I believe that with some work Kaze on n8x0 will become decent enough for everyday use and will provide up to date components long after Nokia has dropped the n8x0 support.

If you have any questions, visit #alip @ freenode.

PS. If you want an open source media engine with D-Bus API checkout the Octopus. It’s a work in progress but handles basic audio and video playback on n8x0 just fine :)

Filed under Maemo
Feb 24, 2009

Linux on ARM

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ARM (and Movial) has published a new site that provides Open Source components, middleware and utilities used to build a Linux Mobile software stack on ARM.

All components (applications, libraries, etc) are in GIT repositories. The build tool is called Matrix. Matrix clones all components under one directory and compiles them with a single command. With another command you get JFFS2 image although that’s not as simple as it should be.

ARM would like to get all contributions directly to upstream instead of providing large code dumps and states that developers are encouraged to participate in discussion forums and developer community of respective components used on this site. That’s why there are no new mailing lists nor forums available for the platform. There is #matrixhelp (#matrix was taken) on irc.ipv6.oftc.net for Matrix related issues though. Developing the components is convenient if you are familiar with GIT. It’s easy to test if your patch works and send it to the upstream project.

One of the supported hardware platforms is n8x0 which is nice as it’s commonly available. The downside is the closed source nature of it. There are two projects, example-project and Kaze that has n8x0 configured as one target platform. Kaze has XFCE desktop instead of Matchbox desktop that the example-project uses.

Kaze boots but most features need still work. WLAN works without encryption but WEP and WPA encryptions need to be fixed. ALSA works with alsa plugins through the DSP but the closed source DSP tasks need to be copied to the build system. Kaze has normal X.Org instead of Xomap, so there’s no XV extension, only stubs.

Filed under Maemo
Aug 20, 2008

2.6.25 and BT working on Gumstix

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I finally got the Bluetooth working with my Gumstix running 2.6.25 and my linux setup. My patches are against two weeks old kernel but hopefully apply to current HEAD too. The patches include my kernel config: gumstix-verdex-bt.config too.

I had to configure the BT hardware using pxaregs and /prog/gpio in my startup scripts (copied from some OE image):


echo -n "Starting 32kHz clock..."
/usr/sbin/pxaregs OSCC_OON 1
while /usr/sbin/pxaregs OSCC_OOK | tail -n 1 | grep -q -v 1;do
echo -n '.'
sleep 1
done
echo "Settled"

/sbin/modprobe gumstix_bluetooth
/sbin/modprobe proc_gpio

echo "AF3 out" > /proc/gpio/GPIO9

echo "AF1 in" > /proc/gpio/GPIO42
echo "AF2 out" > /proc/gpio/GPIO43
echo "AF1 in" > /proc/gpio/GPIO44
echo "AF2 out" > /proc/gpio/GPIO45

I also had to patch my hciattach from bluez-utils 3.29. Those patches are here.

Filed under gumstix
May 8, 2008

UBIFS and Gumstix

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I wanted try something other than JFFS2 as the rootfs and decided to go with UBIFS. Thanks to GIT’s brilliance I had no trouble pulling the UBIFS kernel patches from their tree to mine.

It seems that the UBIFS hasn’t had many NOR flash users before me and it needed some fixes. Artem Bityutskiy was extremely helpful in fixing the deficiencies and helping me out. After a few debug rounds I now have UBIFS root on my Gumstix.

I created the UBIFS image with the following commands:


sudo mkfs.ubifs --compr=zlib -r /tmp/rootfs -m 1 -e 130944 -c 120 -o ubifs.img
ubinize -o ubi.img -m 1 -p 128KiB -v ubinize.cfg

With this ubinize.cfg:


[ubifs]
mode=ubi
image=ubifs.img
vol_id=0
vol_size=13MiB
vol_type=dynamic
vol_name=rootfs
vol_alignment=1
vol_flags=autoresize

Note that I have reserved 2MiB for the kernel partition.

I had to add one extra parameter to the kernel args to specify what MTD partition I wanted to use:

console=ttyS0,115200n8 root=ubi0:rootfs rootfstype=ubifs reboot=cold,hard ubi.mtd=1

Now my Gumstix boots with simplified kernel to busybox shell in roughly 4.2 seconds (counted from the bootm command in U-Boot).

Filed under gumstix
Apr 18, 2008

2.6.25 running on Gumstix

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I had to add a new category after all: gumstix. The embedded word has too broad a meaning.

Updating the kernel wasn’t such a big thing after all, even for a kernel n00b like me. I git cloned the vanilla tree from kernel.org and patched the generic (and one bluetooth) Gumstix patches from OE: arch-config.patch, board-init.patch, header.patch, mach-types-fix.patch, modular-init-bluetooth.patch, tsc2003-config.diff, tsc2003.c, and uImage-in-own-partition.patch. Most of them applied fine, I just had to manually apply simple Makefile patches and change pxa_init_irq call to pxa27x_init_irq.

I don’t know if it really works, but at least it booted:


root@gumstix-custom-verdex:~$ uname -a
Linux gumstix-custom-verdex 2.6.25-rc8-00151-gdc41023 #2 Fri Apr 4 23:43:25 EEST 2008 armv5tel unknown

Filed under gumstix
Apr 8, 2008

Gumstix

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It’s time to create a new category in my projects blog: embedded.

I got interested in microcontrollers some years ago and wrote something simple for 16F88 with assembler. Then I connected it to an old IPAQ using a serial connection. But the IPAQ isn’t a very good development platform so now I decided to buy a gumstix.

Gumstix Verdex

It’s 400Mhz verdex mainboard with 64M RAM and 16M flash. And a bluetooth. The mainboard is the smaller board upside down in the picture. The bigger board is a expansion board including 3x rs232, power plug, a USB mini-B connector and a bunch of GPIO lines.

The bootloader is U-Boot and the Linux distribution is based on OpenEmbedded. U-Boot is nice as I’m somewhat familiar with it but the OE I’m going to replace with something else.

I just booted it up to see how it looks inside:


cat /proc/cpuinfo
Processor : XScale-PXA270 rev 7 (v5l)
BogoMIPS : 415.33
Features : swp half thumb fastmult edsp iwmmxt
CPU implementer : 0x69
CPU architecture: 5TE
CPU variant : 0x0
CPU part : 0x411
CPU revision : 7
Hardware : The Gumstix Platform

Maybe the first thing would be to configure the kernel to support only those features included in my hardware setup.

Filed under gumstix
Apr 3, 2008

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ARM DSP Embedded Linux Gumstix Harmattan Linux Maemo Measurement MeeGo Microcontroller Multimedia My projects N800 N810 N900 N950 Ogg Open Source sharing

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