LAC2014: submission accepted!

My submission for the Linux Sound Night at LAC2014 with The Infinite Repeat has been accepted. The Call for Papers page mentions the term “danceable” so I’m going to focus on that. Making danceable music is quite a challenge for me but it should definitely be doable to produce a solid set, especially now that I’m the proud owner of a Korg Volca Keys. I’m definitely going to integrate it in my current setup as the Volca reacts great on MIDI sent from my workstation. It has some fat sounds that just scream dance floor.

Korga Volca Keys

I’m really looking forward to this year’s LAC. It seems falkTX and avlinux are going too, it’d be great to meet these guys in real life!

LAC2014: submission accepted!

A week without a Mac

Got my new workstation last week. Ultimately I decided to opt for a Dell notebook system with Linux pre-installed. So that left me only one single option: the XPS 13 Developer Edition, aka Sputnik 3. After having worked with it for a week I can only say I’m very, very happy with it. Unboxing it was a joy in itself, unwrapping the amazingly sleek machine and booting it for the first time. The XPS 13 comes with Ubuntu 12.04 LTS pre-installed which is just fine for me, especially given the fact that everything seems to work flawlessly so far. I haven’t rebooted it for days for example, suspending it works brilliantly and when I open the lid the device wakes up instantly, even after having it closed for days. And even though it has an i7 CPU it can run for hours on a full battery. The touch screen is a nice bonus but I haven’t really made use of it yet, it could be quite cool for live perfomances though. I’ve tested the touch screen with seq24 and it’s quite awesome to be able to trigger sequences by pressing the sequences on your screen.

Dell XPS 13 Developer Edition

I did try a fresh install but it would take me a bit too much time to get everything working properly so in the end I opted for sticking with the default install and install the Lubuntu desktop on top of it. And the default install doesn’t get in the way so I’m all set. I’m now looking for a nice keyboard and mouse to pair with the notebook, I’d greatly appreciate any suggestions. I had already ordered a Logitech K290 but I’m sending it back because it has the function keys swapped with the media keys and I just can’t work with that. Switching tty’s with Fn+Ctrl+F[:digit:] is just impossible to do with that keyboard. I could’ve tried swapping the keys but I’ve already filled in the RMA form and repacked the keyboard so it’s going back.

Next up is configuring it for making music. I’m thinking about purchasing a new USB audio interface, preferably USB2.0, that matches well with this machine. Suggestions are very welcome. I’ve looked at the Focusrite Scarlett 2i4 but a recent thread on LAU raised some doubts. We’ll see, it’s something for later, for now I’m extremely happy with my new work horse.

A week without a Mac

Resolved JACK issues on notebook

Finally got around troubleshooting the issues I was facing with JACK on my notebook, a BTO that is actually a Clevo W170ER. Somehow I couldn’t go lower than -p128 with USB audio interfaces. When I thought I had tried every option, even disabling hyperthreading, I noticed two unidentified entries in my lsusb output:

Bus 001 Device 003: ID 8087:07da Intel Corp. 
Bus 002 Device 003: ID 5986:0401 Acer, Inc

The first entry is a Bluetooth adapter and the second entry is a webcam. Both devices are unnecessary when making music so I thought, why not unbind them. First I had to figure out their respective bus ID’s:

$ tree /sys/bus/usb/drivers/usb
??? 1-1 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1
??? 1-1.3 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.3
??? 2-1 -> ../../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1
??? 2-1.6 -> ../../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.6
??? bind
??? uevent
??? unbind
??? usb1 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1
??? usb2 -> ../../../../devices/pci0000:00/0000:00:1d.0/usb2
??? usb3 -> ../../../../devices/pci0000:00/0000:00:14.0/usb3
??? usb4 -> ../../../../devices/pci0000:00/0000:00:14.0/usb4

Since the Bluetooth adapter sits on bus 1 and the webcam on bus two their respective ID’s should be 1-1 and 2-1. So I echoed the ID’s to the unbind file in the same directory:

$ echo -n "1-1" | sudo tee /sys/bus/usb/drivers/usb/unbind
$ echo -n "2-1" | sudo tee /sys/bus/usb/drivers/usb/unbind

Good riddance:

$ lsusb
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub

Then I started JACK again with -p64 using an USB audio interface connected to bus 3 (so no rate matching hub in between) and no more xruns, not even with a generic kernel and using WiFi and all. Next hurdle is the onboard sound. Below -p128 I get bursts of massive xruns and so far I didn’t manage to pinpoint the culprit.

Edit #1: I’ve found out that the Bluetooth adapter is the main bottleneck. Also, by echoing the aformentioned ID’s (1-1 and 2-1) you disable the whole USB bus apparently. To disable just the USB device echo the last ID in the respective path names, so for the Bluetooth adapter that’s 1-1.3 and for the webcam 2-1.6. This way you can still use the USB bus on which these devices are residing. In my case disabling the whole bus is not an option, this would mean I’d have to connect all my USB interfaces to bus 3 (bus 4 doesn’t have any external inputs) which could result in these devices getting in each other’s way with regard to bandwidth. After echoing the ID’s the output of the tree command looks like this:

$ tree /sys/bus/usb/drivers/usb
??? 1-1 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1
??? 2-1 -> ../../../../devices/pci0000:00/0000:00:1d.0/usb2/2-1
??? bind
??? uevent
??? unbind
??? usb1 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1
??? usb2 -> ../../../../devices/pci0000:00/0000:00:1d.0/usb2
??? usb3 -> ../../../../devices/pci0000:00/0000:00:14.0/usb3
??? usb4 -> ../../../../devices/pci0000:00/0000:00:14.0/usb4

The lsusb command still shows the devices though.

Edit #2: unbinding drivers like described above won’t persist across reboots. If you’d like to make the unbinding persistent you could add the unbind command to /etc/rc.local or create a script that runs at login. There are other options of course like blacklisting the Bluetooth drivers.

Resolved JACK issues on notebook

Finally got an acoustic-electric

Last sunday I was like, I’m going to one of my favorite music stores and try me some acoustic-electric guitars. A good acoustic-electric guitar has been on my wishlist for like, ages. Of course I first checked on the site of the music store what they had to offer and at that moment I basically made a choice already because I had a hunch that the guitar of my choice would stand out because of its specs (hand-built, solid spruce top, mahogany neck, sapele sides and back). When I wandered into the music store and started checking out the acoustic-electrics the sales guy quickly approached me asking the inevitable question what I was looking for.

I told him my budget and he immediately picked the guitar I had checked out on the site. He handed it over to me and I was sold. The next one hour and a half were pure bliss, only tempered by a brief intermezzo with a Martin D-16GT which sounded like a cardboard box compared to the guitar I wanted. So I just bought it.

Eastman AC320CE

The AC320CE ships with a Fishman Matrix VT under-the-saddle pickup system which isn’t the best sounding solution but for the intended purpose of this guitar (using it on stage) it’s probably better than a solution that includes an internal mic. So no, I wasn’t blown away by the sound once it was plugged in but yesterday I bought a Fishman Aura Acoustic Imaging Pedal Concert preamp/DI for cheap so I should be covered. It’s actually an older model that can be upgraded to an Aura Sixteen.


Fishman Aura Acoustic Imaging Pedal Concert

So I’m a happy camper. The guitar plays like a dream, sounds sublime unplugged and looks very good. I really like its neck which feels a lot like the one on my Sigma DR-41 (an old one, so not a recent, re-released Sigma). The tone is very well balanced, lows are well present and the highs just shimmer the way I like it. And normally I don’t really dig Venetian style bodies but the body of the Eastman is just very well proportioned. Awesome guitar. Oh yeah, I got 10% off the price, that always helps in making these kind of decisions.

Finally got an acoustic-electric

A month on a Mac

During the second job interview with my new employer I was asked if I’d like to use a Mac or a Windows PC with the assurance I’d get a Linux workstation after my probation time. Just put me behind a Mac then, that’s closer to Linux than Windows and from what I recalled it comes with a native terminal that does SSH. And what do I need more?

So there I am in front of a big, glossy screen and a tiny keyboard that lacks some familiar keys. My findings so far? Kind of neutral. I’ve got my terminal and I can run SSH from the CLI so I’m happy. There are some quirks that annoy me though (in no particular order):

  • No Compose key and I had to jump through quite some hoops to map a key as a Compose key.
  • No easy way to map a keyboard shortcut for opening a terminal. I had to resort to something called ‘Automator’ to get it working. And it still doesn’t work the way I want too. When there are no windows open pressing the shortcut doesn’t do anything. When there are open windows it works but why does it open two terminals when pressing the shortcut for the first time? Not a real big deal as I need multiple terminals anyway (I just can’t get used to tabbed terminals).
  • I prefer non-glare monitors to glossy ones.
  • No Home, End, PageDown and PageUp keys. Not a real big deal either, in fact, it’s a real good incentive to start getting accustomed to Vi(m) shortcuts since I kind of live inside Vim these days. I even bought this, great stuff.
  • Can’t get used to the default window management settings. For instance when you minimize a window and Alt+Tab to it the window doesn’t open. So I’m not minimizing any windows anymore since this is really annoying. Haven’t looked into changing this behaviour though, it’s probably something relatively simple.
  • Annoying pop-ups from updates and programs that are downloaded from the internet (“blabla” is an application downloaded from the Internet. Are you sure you want to open it?). Especially the latter ones are annoying. Disabling the pop-ups has to be done from a terminal. Wow, so much for a “user-friendly” OS.
  • Clicking the close button of an application doesn’t quit it. Cmd+Q does. This is something I won’t get used to either. Actually I don’t want to get used to the Cmd button at all.
  • I prefer a panel with a window list on it. I don’t know how other folks do it but this Alt+Tab stuff is counter-efficient in my case.

Are there things I particularly like about Mac OS X or the Mac itself? Actually no, can’t think of anything. Yeah, the keyboard feel is really nice but that pro gets nulled out because of the missing keys, ~ being placed next to the left Shift key and the Fn keys being mapped to the F1/F12 keys. Add to this the meaningless keys with all kinds of arrows on them and this key with a crossed square. No idea what they do. On a software level MacPorts is nice, it allowed me to install some of my favorite tools that I found were missing. Other than that I can’t wait to have my own workstation with Linux on it. The plan is that I get a Dell XPS 15 with a dual monitor setup. Something to look forward to.

And yes, I have to deal with quite some Windows servers now. I’m not going to dedicate a blogpost to my findings on that OS. Just one word. Meh.

A month on a Mac

Using a Raspberry Pi as a piano

Recently I posted about my successful attempt to get LinuxSampler running on the Raspberry Pi. I’ve taken this a bit further and produced a script that turns the Raspberry Pi into a fully fledged piano. Don’t expect miracles, the sample library I used is good quality so the RPi might choke on it every now and then with regard to disk IO. But it’s usable if you don’t play too many notes at once or make extensive use of a sustain pedal. I’ve tested the script with a Class 4 SD though so a faster SD card could improve stability.

Edit: finally got around buying a better SD card and the difference is huge! I bought a SanDisk Extreme Class 10 SD card and with this SD card I can run LinuxSampler at lower latencies and I can play more notes at once.

Before you can run the script on your Raspberry Pi you will need to tweak your Raspbian installation so you can do low latency audio. How to achieve this is all described in the Raspberry Pi wiki article I’ve put up on After you’ve set up your RPi you will need to install JACK and LinuxSampler with sudo apt-get install jackd1 linuxsampler. Next step is to get the Salamander Grand Piano sample pack on your RPi:

mkdir LinuxSampler
cd LinuxSampler
wget -c
wget -c
tar jxvf SalamanderGrandPianoV2/SalamanderGrandPianoV2_44.1khz16bit.tar.bz2
tar jxvf sgp44.1khz_V2toV3.tar.bz2 -C SalamanderGrandPianoV2_44.1khz16bit

Please note that decompressing the tarballs on the RPi could take some time. Now that you’ve set up the Salamander Grand Piano sample library you can download the script and the LinuxSampler config file:

mkdir bin
wget -c -O /home/pi/bin/piano
chmod +x bin/piano
wget -c
/SalamanderGrandPianoV3.lscp -O

Almost there. We’ve installed the necessary software and downloaded the sample library, LinuxSampler config and piano script. Now we need to dot the i’s and cross the t’s because the script assumes some defaults that might be different in your setup. Let’s dissect the script:


if ! pidof jackd &> /dev/null
  sudo killall ifplugd &> /dev/null
  sudo killall dhclient-bin &> /dev/null
  sudo service ntp stop &> /dev/null
  sudo service triggerhappy stop &> /dev/null
  sudo service ifplugd stop &> /dev/null
  sudo service dbus stop &> /dev/null
  sudo killall console-kit-daemon &> /dev/null
  sudo killall polkitd &> /dev/null
  killall gvfsd &> /dev/null
  killall dbus-daemon &> /dev/null
  killall dbus-launch &> /dev/null
  sudo mount -o remount,size=128M /dev/shm &> /dev/null
  echo -n performance
| sudo tee /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor &> /dev/null
  if ip addr | grep wlan &> /dev/null
    echo -n "1-1.1:1.0" | sudo tee /sys/bus/usb/drivers/smsc95xx/unbind &> /dev/null
  jackd -P84 -p128 -t2000 -d alsa -dhw:UA25 -p512 -n2 -r44100 -s -P -Xseq
&> /dev/null &

This is the first section of the script. An if clause that checks if JACK is already running and if that’s not the case the system gets set up for low latency use, a simple check is done if there is an active WiFi adapter and if so the ethernet interface is disabled and then on the last line JACK is invoked. Notice the ALSA name used, hw:UA25, this could be different on your RPi, you can check with aplay -l.

jack_wait -w &> /dev/null

jack_wait is a simple app that does nothing else but checking if JACK is active, the -w option means to wait for JACK to become active.

if ! pidof linuxsampler &> /dev/null
  linuxsampler --instruments-db-location $HOME/LinuxSampler/instruments.db
&> /dev/null &
  sleep 5
netcat -q 3 localhost 8888
< $HOME/LinuxSampler/SalamanderGrandPianoV3.lscp &> /dev/null &

This stanza checks if LinuxSampler is running, if not LinuxSampler is started and 5 seconds later the config file is pushed to the LinuxSampler backend with the help of netcat.

while [ "$STATUS" != "100" ]
  STATUS=$(echo "GET CHANNEL INFO 0" | netcat -q 3 localhost 8888
| grep INSTRUMENT_STATUS | cut -d " " -f 2 | tr -d 'rn')

A simple while loop that checks the load status of LinuxSampler. When the load status has reached 100% the script will move on.

jack_connect LinuxSampler:0 system:playback_1 &> /dev/null
jack_connect LinuxSampler:1 system:playback_2 &> /dev/null
#jack_connect alsa_pcm:MPK-mini/midi_capture_1 LinuxSampler:midi_in_0 &> /dev/null
jack_connect alsa_pcm:USB-Keystation-61es/midi_capture_1 LinuxSampler:midi_in_0
&> /dev/null

This part sets up the necessary JACK connections. The portnames of the MIDI devices can be different on your system, you can look them up with jack_lsp which will list all available JACK ports.

jack_midiseq Sequencer 176400 0 69 20000 22050 57 20000 44100 64 20000 66150 67 20000 &
sleep 4
jack_connect Sequencer:out LinuxSampler:midi_in_0
sleep 3.5
jack_disconnect Sequencer:out LinuxSampler:midi_in_0
killall jack_midiseq

This is the notification part of the script that will play four notes. It’s based on jack_midiseq, another JACK example tool that does nothing more but looping a sequence of notes. It’s an undocumented utility so I’ll explain how it is invoked:


<command> <JACK port name> <loop length> <start value> <MIDI note value> <length value>

jack_midiseq Sequencer 176400 0 69 20000 22050 57 20000 44100 64 20000 66150 67 20000

JACK port name: Sequencer
Loop length: 4 seconds at 44.1 KHz (176400/44100)
Start value of first note: 0
MIDI note value of first note: 69 (A4)
Length value: 20000 samples, so that's almost half a second
Start value of second note: 22050 (so half a second after the first note)
MIDI note value of second note: 57 (A3)
Length value: 20000 samples
Start value of third note: 44100 (so a second after the first note)
MIDI note value of second note: 64 (E4)
Length value: 20000 samples
Start value of third note: 66150 (so one second and a half after the first note)
MIDI note value of second note: 67 (G4)
Length value: 20000 samples

Now the script is finished, the last line calls exit with a status value of 0 which means the script was run successfully.

exit 0

After making the script executable with chmod +x ~/bin/piano and running it you can start playing piano with your Raspberry Pi! Again, bear in mind that the RPi is not made for this specific purpose so it could happen that audio starts to stutter every now and then, especially when you play busy parts or play more than 4 notes at once.

Using a Raspberry Pi as a piano: quick demo

Using a Raspberry Pi as a piano

Raspberry Jam Review

Last Thursday the first Dutch Raspberry Jam took place at the Ordina HQ in Nieuwegein. I offered to do a presentation slash demonstration about realtime audio and the the Raspberry Pi so I promised myself to be there at least an hour before the scheduled starting time of my demo. That way I could also join Gert van Loo‘s presentation. When I arrived at 19:15 there was no Gert van Loo though so that should’ve triggered some alarms. Also I didn’t look out for members of the organization as soon as I came in. Instead I chose to dot the i’s and cross the t’s with regards to my demo.

Wrong decision.

About half an hour later the event was closed.


I approached the person who closed the event and introduced myself. He replied that they thought I wasn’t coming anymore. Apparently they misinterpreted my e-mail I sent earlier that day that I didn’t manage to produce something workable for the laser show guy. They took it for a cancellation. But immediately the event got kind of reopened and I set up my stuff. We had some audio issues but in the end everything went quite well actually. I showed off what is possible with a Raspberry Pi and realtime audio with the use of some of my favorite software. Guitarix featured of course. I grabbed my guitar, fired up guitarix on the RPi and played some stuff. Hooked up my MIDI foot controller and showed how to select different presets. I also demonstrated the use of the RPi as a piano with the help of LinuxSampler and the awesome Salamander Grand Piano samplepack and did some drumming by using drumkv1. Before the realtime audio demo I presented an overview of the Linux audio ecosystem and talked about the alternatives of how to get sound in and out of your Raspberry Pi. These alternatives are not bound to the onboard sound and USB, since recently it is also possible to hook up an external audio codec to the I2S bus of the Raspberry Pi. I got one in myself this week, a MikroElektronika Audio Codec PROTO board based on the WM8731 codec, so more on that soon. It’d be awesome if I can get that codec to work reliably at lower latencies.

So it all turned out well, I had a great time doing my presentation and judging by the interest shown by some attendants who came up to me after the presentation I hope I got some more people enthusiastic about doing realtime audio with the Raspberry Pi and Linux. So thanks Ordina for offering this opportunity and thanks everyone who stuck around!

Raspberry Jam Review

Exit BeagleBone Black, hello Cubieboard2!

Put up my BeagleBone Black for sale. It was gathering dust, somehow this board doesn’t appeal to me. Biggest drawback is that it seems to be very picky with power adapters. If you don’t use a linear power adapter USB devices might not work properly. And that was exactly the issue I was facing, I just couldn’t get my USB audio interfaces to work on the BBB. So I lost interest because well, that’s what I bought the device for, to get sound out of it with the help of an USB audio interface. Add to this that there is no realtime kernel or RT patchset available for the BBB and that the BBB is quite a complex little device (it’s actually a REAL dev board). It would’ve cost me too much time to completely fathom it. No bad feelings though, the BBB is a very nice product and it sure has the slickest looks of all ARM SoC dev boards around.

Also I got a Cubieboard2 in recently. And that board has absorbed me for the last week and a half. It’s quite easy to set up (not as easy as the RPi though), has a lot of IO (yes, it has audio in and out!) and it blows both the RPi and BBB away when it comes to performance with its dual core A20 Allwinner SoC that can easily be overclocked to 1.2 GHz. Alas, no realtime kernel or RT patchset either but hey, I managed to get a RT kernel running on a Rockchip RK3066 based device so I could at least give it a try. And it worked out well. I’m now running a 3.4.61-rt77 kernel on it with a custom Debian Wheezy installation. This time I used git to keep track of the modifications I made so it was a lot easier to create a usable diff. I also patched the driver for the onboard audio codec because the hardcoded defaults were just unusable for realtime audio. Minimum number of periods was 4 and minimum buffer size was 1024. Don’t ask me why. So I’ve changed these to 2 and 16 respectively and managed to get JACK running at a respectable -p64 -n2 -r44100. Fired up some JACK clients and this little monster keeps up very well. USB audio interfaces are no problem either, I can run my Edirol UA25 in Advanced mode with -p64 -n3 -r48000 without any hitch. This is probably because the Cubieboard2 doesn’t use a Synopsys DesignWare OTG controller with out-of-tree dwc_otg drivers like the RPi but a better supported USB controller. At the moment the Cubieboard2 is the nicest ARM dev board I have laid my hands on so far.

text-align: center;


RT patchset 3.4.61-rt77 for linux-sunxi, sunxi-3.4 branch

Low latency defaults patch for sunxi-codec driver

Exit BeagleBone Black, hello Cubieboard2!

More ARM goodies II

Received the BeagleBone Black (BBB) and the MK808 with a RK3066 SoC. My first impressions are really positive. Especially the BBB is quite an awesome device that I’m probably going to use a lot in favor of the Raspberry Pi. At first glance I had something like, the BBB blows the RPi away, but as soon as I started looking for documentation on how to put Debian on it for instance it became clear that the RPi is still the device to beat. The RPi community is huge, documentation for it is well laid out and working with the RPi is just so easy. The BBB on the other hand lacks a vivid community, is $10 more expensive and a lot more difficult to work with. Take the Debian install for example, seems quite some work to get that going.

The MK808 is surely an improvement over the UG80X I already own. It comes with a HDMI port instead of a HDMI plug, has an extra USB OTG port, a heatsink, hardware serial console access, a reset button and a power indicator LED. The pre-installed Android version looks better too. I flashed my RT kernel recovery image on it, inserted the Micro SD from my UG80X and it booted without any issues. So I’m going to pursue my goal to get a real-time, low-latency environment running on a RK3066 based device on the MK808 and find another purpose for the UG80X.

Edit: Getting Debian to work on the BBB is actually quite easy:
Next time I’ll promise to make better use of my Google skills.

More ARM goodies II

Hacking an Android TV stick, the sequel

jeremy@rk3066:~$ uname -a
Linux rk3066 3.0.36-rt58 #1 SMP PREEMPT RT Thu Jul 4 13:18:23 CEST
2013 armv7l GNU/Linux

Managed to compile and run a real-time kernel on the Android TV stick with the RK3066 SoC. Packaged the latest version of amSynth (1.4.0 which has been released recently), installed it, fired up JACK and amSynth and so far no xruns, nothing. And this is with -p64!

jackd -P84 -p32 -t2000 -dalsa -dhw:Device -n3 -p64 -r44100 -s -P

I should measure the latency of the $2 USB audio interface I’m using to find out what the total latency of this set-up is. Well, at least I got the system latency for usage with softsynths like amSynth down to 64/44100*2=3ms. Now that’s a usable situation.

jeremy@rk3066:~$ lsusb | grep -i c-media
Bus 002 Device 006: ID 0d8c:000e C-Media Electronics, Inc. Audio Adapter (Planet
UP-100, Genius G-Talk)
jeremy@rk3066:~$ cat /proc/asound/cards 0 [RK29RK1000 ]: RK29_RK1000 - RK29_RK1000 RK29_RK1000 1 [HDMI ]: ROCKCHIP_HDMI - ROCKCHIP HDMI ROCKCHIP HDMI 2 [Device ]: USB-Audio - Generic USB Audio Device Generic USB Audio Device at usb-usb20_host-1.1, full speed

A big pro of this stick is that it suffers less from SD card corruption than my RPi. Yesterday evening I wrecked up yet another SD card when testing my RPi with a real-time kernel, it’s getting a bit cumbersome. Speaking of real-time kernels, it was quite some work to apply the RT patchset to the RockChip kernel source. Had to add stuff by hand and when I finally got everything in place it wouldn’t compile. But I managed to solve all the build errors. After flashing the kernel image the TV stick wouldn’t boot of course, it hung at some point. But I quickly saw that the issue was with the SD card reader and that it was similar to the SD card reader issue on the RPi for which I found a workaround. So I added an #ifdef clause to the RockChip SD card reader driver, recompiled, reflashed and wham, it continued booting. Now I have to clean up my build directory and get a usable diff of it against the pristine RK3066 kernel sources.

Hacking an Android TV stick, the sequel