MK808 rk30xxHMDI driver - Fixing black screen/no image problem 
From day one I had difficulties working with the MK808. None of my LCD displays worked with the device. All gave a black screen, no image at all. The only exception was my Samsung TV set. Not so handy when developing stuff for the MK808, tweaking the kernel, changing the Android OS or even create new distributions like Ubuntu or XBMC.

So in the beginning I used 'adb' a lot, and walked over to the TV set in the living room like a million times, asking my wife again and again if it's okay to "borrow" the TV for just a minute and test my latest change(s) ;-)

Now, having the serial console feature, debugging has become so much easier. The console is available early in the kernel boot process, and the device is accessible from my PC. A lot of mistakes you make when customizing the kernel show up on the console, which is very helpful.

This is how I found out that, although no image showed up on my LCD monitor, detaching the monitor was detected by the HDMI driver. This made me think. Could it be a flaw in the HDMI driver after all? All the "solutions" I read about online were related to adding (powered!) splitters, (powered!) repeaters or other converters/adapters to the MK808. In my opinion, one of the nice things of a device like this is that is has an ARM CPU which uses very little power. The succes of having such device 100% working for me would be having a small extremely powerful, "always on" and very low powered device. That's why adding all kinds of additional powered hardware is a real show stopper to me.

Delving into the HDMI device driver code, I looked at the "hotplug" feature. This feature signals any changes on the HDMI port, connecting or disconnecting a display for instance. I changed the code by telling the driver that a display is always connected, in effect disabling the hotplug feature. I also set the resolution fixed to 1280x720 60Hz (1080p720p). This works! Booting the customized kernel now finally shows the Android home screen on all my displays.

For all of you having the same black screen/no image problem, please try flashing the kernel, and let me know if this fixes the problem for you as well. Included in this 3.0.8+ kernel are a lot of additional patches and changes, cherry picked from the 3.0.50 kernel release. I'll continue to upgrade the kernel to a higher level.

[Update] 2013-01-20 Sound issue fixed.

The kernel can be downloaded here.

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MK808 Endeavours... 
As some of you know, I've been working on the MK808 TV Stick/Mini PC for some time now. The MK808 is based on the dual-core Rockchip RK3066. A quite powerful SOC, capable of doing the average stuff most of us do every day with a desktop PC. Unfortunately, Rockchip is one of those manufacturers that don't comply to any open source license agreement. Simply put, the rule of thumb is that when you use open source you have to give all the modifications you make when selling products based on GPL back to the community. Well, Rockchip doesn't comply to these rules. Worse, they make their own license rules, saying that they are the sole owner of all software, including all GPL parts. That's why most hardware manufacturers say they aren't allowed to give any of the sources. Too bad they don't seem to understand the value of working together on making things better. Oh well, enough of this, I think I made my point clear. It's just so frustrating!


Luckily there are a few hardware manufacturers that understand the value of GPL. Or it may be that they don't understand the chinese license agreement from Rockchip. Or it may just be that they understand the underlying GPL agreement, unlike Rockchip. It may be a coincident also, but all the manufacturers providing some of the Rockchip adaptations of the Linux kernel seem to be based outside the people's republic of China. Anyway, it doesn't matter how, what matters is that we finally have a few snapshots of the Rockchip linux kernel adaptations after all.

Unfortunately, from all current available snapshots a lot of the essential code is missing. This makes it a difficult process to get all the hardware components working. Some code parts are delivered in binary object files only, which prevents you from making changes without going through the time consuming process of disassembling and reverse engineering.

I tried to upgrade the MK808 kernel to a higher version of the linux kernel a while ago. Reason for this is to apply common (mainline) patches and enhancements and to add some new features as well. I failed miserably. The device didn't boot, and I came to the point that I had no ways to find out what error(s) I had made. The kernel died early in the boot process. This is a common problem in kernel development. One way to find out what goes on during the boot process is the use of a serial console. I saw this great blogpost a while back about the UG802. It's a similar device using the same Rockchip RK3066 CPU. Although the PCB layout is completely different of course, I imagined that PCB designers would always create ways to debug low-level problems like I had. This is easy to say with the little knowledge of hardware that I have ;-) I looked at detailed images of the MK808 PCB and saw some connector pins that could indicate the possible use of a serial console.


This is where my brother comes in. He has a strong hardware background, always messing around with Arduino's and the like. I asked him if it was as easy as I thought it would be. The short answer was... No, it's not "just" soldering three wires onto the MK808 mainboard and connect them to the serial port of a PC. You have to know, I'm a software guy, so in terms of background my brother and I come from two completely different worlds. He tried to explain the importance of voltage conversion for instance. The PC using 12V whereas the MK808 only uses 3.3V. Talking about the risk of blowing up the device if not being careful. Or why it doesn't make sense to "just" replace the Wifi antenna with a bigger model. I have to say, most of this is all way beyond the scope of my understanding!

Anyway, to cut an already long story a little shorter, my brother came visiting me saturday afternoon and we took the plunge and started to mod the MK808. What I suspected was that the three pins just outside the CPU area were meant for debug purposes. Like on the UG802. This was a long shot of course, but that was just my simplistic way of thinking :-)

With my newly bought soldering iron, multimeter, connectors and a FTDI serial to USB breakout board we started checking out these three pins. We were in luck. The first pin we checked was the receive (RX) pin for a serial console. Tadaaaa! The MK808 booted, and we saw console output on the PC. Wow! After that it was easy to guess the transmit (TX) pin, having only two more pins left, leading to a complete working serial console in no time. How cool is that!


Most time went into putting everything back together. The heatsink had to be put back in place and we needed to get the wires connected to the FTDI board outside the case. We made a connector on top of the device so the FTDI board can now be easily connected and removed if needed. Look for yourself, I think it looks slick, and more importantly, it works perfectly well!

I couldn't have done this without the help of my brother, so all credits go to him. Thanks bro, a job very well done!

Now back to kernel hacking, so hopefully more on that later :-)

For a detailed series of hi-res photo see here


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[update] Huawei G300/U8815 kernel (added zRam) 
I've added "zRam" to the kernel. This feature was previously known as "compcache". It increases performance by avoiding paging on disk and instead uses a compressed block device in RAM in which paging takes place until it is necessary to use external (disk) swap space.

I'm still testing it, but it seems to have a positive effect in terms of performance.

You have to enable it manually for now. Use a terminal emulator or use "adb shell" to do this more comfortably from your desktop.

To setup a 100Kb (100*1024*1024) zRam:
echo 104857600 > /sys/block/zram0/disksize
mkswap /dev/block/zram0
swapon /dev/block/zram0


To disable the zRam:
swapoff /dev/block/zram0

Remember this won't survive a reboot, so you have to re-enable it again after reboot.

Download the kernel here (MD5: a89bd97f940cc33c11ca7cc73d521abb)

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[update] Huawei G300/U8815 kernel (camera flash fixed) 

I got in touch with "genokolar" today, since he managed to get the camera flash fixed on the U8818. He was kind enough to send me his patches, so all credits go to him for this release. I also added some more overclock frequencies, up to 1.5GHz, but they result in reboots only. At least for now...

I've created a repository on github, so please feel free to fiddle around with the sources yourself.

Download the kernel here (MD5: da9199471e4ce538d2a16bfc1d3dc1c3)


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[update] Huawei G300/U8815 kernel 
A quick update of the G300/U8815 kernel. This update fixes bluetooth. Tested this afternoon, and it works perfectly now. Tomorrow I will look into the camera flash that's not working. I will also start stripping the kernel a bit, removing unnecessary parts that only take up precious memory. Maybe I try to add some extra overclocking as well, although I don't think the current "lagging" most of us see every now and then is fixed by only increasing the CPU frequency.

Download the kernel here (MD5: ccd3c44e20ce1b79b0030341f4c6f68e)

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Overclock Huawei G300/U8815 with new kernel to max 1.3GHz 
In the top 10 excuses for not blogging for so long my excuse would be... well, I don't have an excuse, I'm still here and that's what counts :-)

I've build a kernel for my Huawei G300/U8815 smartphone yesterday. Based on the Huawei v3.0.8 kernel code, I've added overclocking, governers and I/O schedulers and added some minor tweaks here and there. Not a lot of other features yet, but I'm quite surprised with the results so far in battery life and performance. So see for yourself. Tested with stock Huawei B927 ROM, up to 1.3GHz.

Tested for performance with max 1.306GHz and min 480MHz frequency, governor "Performance" and I/O Scheduler "VR" I get a AnTuTu score of 3542. This is with lots of applications installed and active. Not bad at all I think :-)

Tested for battery life with max 1GHz and min 122MHz frequency, governor "SmartassV2" and I/O Scheduler "VR" for 11 hours. Battery dropped 0%(?!) during that time. While not sure if that's really correct and representative I started using the browser intensively, made a 5min telephone call and used whatsapp. Battery dropped from 75% to 68% during that time. Needs more testing I guess, but please post your results here!

Use something like "No-frills CPU control" from the Market to quickly set the CPU frequencies, Governor and I/O Scheduler to use. Try different options to find out which combination works out best for your specific situation(s).

I packaged the kernel as an "update.zip" so it can be easily flashed from CWM. It only updates the kernel, no need to clear caches or wipe data or anything. Just make sure to have a backup in case you want to go back to the stock kernel.

Needless to say maybe, but I'll do it anyway... Be careful with overclocking your device. Overclocking will cause a CPU to have a shorter life expectancy. Apart from that, I take no responsibility whatsoever if you fry your CPU

Last but not least a shameless plug... there is this nice "Donate" button on the left side of this page. Feel free to use it if you like what you see.

More to come...

Download the kernel here (md5: 1a00982486bbff62907624c2507ebbd9)

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Ubuntu Lucid Lynx (v10.04) on Zaurus... 
Having my GuruPlug all set up I started building Ubuntu Lucid Lynx (v10.04) some time ago. From scratch, compiled natively, that is. It took me quite some time to get myself acquinted with (re)packaging first, but now I kind of seem to manage my way through it most of the time.

Ubuntu Jaunty (v9.04) was the last version that supports armv5te CPUs. The current versions only runs on the newer ARM processors (armv7+). So that meant I had to re-target all armv7 specific packages to make them work on the (older) armv5te CPUs again. Since this is the only way to get the newer Ubuntu versions going on our beloved Zaurus, it had to be done!

What a work! It probably can be done much quicker, but here's what I did. I took a debootstrap of the ARM (armv7+) version of the official Ubuntu Lucid version to begin with, and started rebuilding all packages one by one, re-targetting them for the armv5te CPUs. Some of the packages need special attention, and others can "just" be recompiled. I have to say, the GuruPlug is really a marvellous piece of hardware, and just perfect for doing this kind of stuff. It's just great not having to concentrate on all these cross-compilation problems you have to deal with when building ARM packages on the i586 platform. I can assure you, the GuruPlug saved me quite some headache!

Before you're going to ask me where all the fun stuff can be downloaded, this post is first of all meant as a status update of the project. Currently I only have the minimal Ubuntu distribution working. All compiled from the original Ubuntu sources, with just minimal changes to some of the packages.

So, no, the complete repository isn't available yet. But I just wanted you all to know that the good news is that it is still possible to get the latest and greatest version of Ubuntu working on our Zaurus. Woohoo!

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The sky is the limit... 
My PlugComputer arrived last friday. The GuruPlug Server Plus to be exact. What a great little gadget that is. I'm still experimenting, but I'm amazed by the speed. Bottleneck now seems to be the harddrive I'm using, which is a cheap USB drive. So I'll have to pick up a eSATA drive I guess.

Oh, and regarding all reported problems on overheating... no problems here!

This means new possibilities for Zubuntu... More on this later!

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Android 1.6 "Donut" on Zaurus 
Just a quick note to say I managed to get Android 1.6 aka Donut working. I tested it on my Zaurus SL-C860. I had to add support for Android in the (2.6.31-rc9) kernel and fix some small glitches in the code to get it boot. There are still lots of things to fix though. On first impression the keymapping is wrong, the touchscreen doesn't respond and it boots in portrait on default. It took quite a while to find out how to get Alsa (sound) working, but that seems to be fixed finally.

So, there are lots of things to do, meaning I have to spend more hours experimenting, debugging, configuring. -sigh-

First try on getting the htc-hero theme running didn't work. Would by nice to have that working as well...

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Zubuntu working on c7x0 as well 
This is just a quick post from my holiday address in Italy, using my SL-C860 on a wifi network in Montefalco, Umbria. It's kind of difficult to type, and the wifi connection is really bad, so I have to keep this short. In one of my late-night experiments I succeeded in getting Zubuntu work. Be patient though, it will take at least another week to upload anything new.

Oh, and yes, I will provide patches and source... When I'm ready. Power management is still not 100% working, so I need more time to fix it. The kernel config can be extracted using the config-module.

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