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by selvmarcus
Wed Jan 18, 2012 5:10 am
Forum: General discussion
Topic: Real-time linux kernel
Replies: 47
Views: 53215

Re: Real-time linux kernel

<r>What kernel version will we likely see for the release?<br/> <br/> Will you supply your patches upstream? This would allow the real-time patch developers to have an eye on them.<br/> <br/> How easy will be migration to newer (and therefore more real-time capable) kernels?<br/> <br/> You can acces...
by selvmarcus
Tue Jan 17, 2012 2:34 pm
Forum: General discussion
Topic: How to protect the filesystem without a save shutdown button?
Replies: 61
Views: 26422

Re: How to protect the filesystem without a save shutdown button?

<t>So, this board needs a shutdown button, that's a simple, cheap thing to attach to one of the GPIO pins. Should need a bit of pressure to engage. Will cause interrupt and then "shutdown -h now" or whatever you tell it to do. After you get some feedback (LED?), you can safely pull the plug. (Could ...
by selvmarcus
Tue Jan 17, 2012 11:15 am
Forum: Other projects
Topic: Harness the power of the GPU?
Replies: 17
Views: 6633

Re: Harness the power of the GPU?

Thanks for the helpful link.

Marcus
by selvmarcus
Mon Jan 16, 2012 3:36 am
Forum: General discussion
Topic: Support Linux Kernel 3.0.x series (longterm release) + boot option for realtime kernel, for release
Replies: 0
Views: 884

Re: Support Linux Kernel 3.0.x series (longterm release) + boot option for realtime kernel, for release

<r>Hello, I just found out about the possible long time stable support for different kernel versions.<br/> <br/> This means bugs are fixed with drivers and the kernel internals by the kernel developer community for the next 2 years, at the moment the only viable choice would be the 3.0 series, curre...
by selvmarcus
Sun Jan 08, 2012 10:16 pm
Forum: Off topic discussion
Topic: I had a dream......
Replies: 12
Views: 2559

Re: I had a dream......

<t>Thanks for sharing your dream, really interesting. I usually try to restrain myself to stay out when this "goldrush" effect is happening.. but I do not always succeed in this.<br/> <br/> It will be crazy, I was already thinking do I need to get an automatic  SMS notification system installed for ...
by selvmarcus
Sun Jan 08, 2012 7:31 pm
Forum: General discussion
Topic: Has a Device Tree been built for the Raspberry Pi.
Replies: 11
Views: 2266

Re: Has a Device Tree been built for the Raspberry Pi.

<t>JamesH said: <br/> <br/> <br/> davidgoodenough said: <br/> <br/> <br/> If we want to use standard distributions we need to use standard kernels.  There may be binary drivers in there (some will object but the reality is that we are going to be stuck with this) but we need to have the basic suppor...
by selvmarcus
Sun Jan 08, 2012 7:13 pm
Forum: General discussion
Topic: Installing or running other distros
Replies: 15
Views: 3301

Re: Installing or running other distros

<t>Please, instead of giving out another official kernel from time to time, what would mean we are all dependent on this and that issues with USB devices, drivers, kernel bugs... get fixed only with you providing a new version, get your board info into *the* official kernel, the one in the care of L...
by selvmarcus
Sun Jan 08, 2012 9:29 am
Forum: Off topic discussion
Topic: Linking a Pi to the Physical world
Replies: 12
Views: 3370

Re: Linking a Pi to the Physical world

<r>Is it possible somebody could be doing the test what the maximum jitter on the Pi's GPIO pins is, with a recent linux realtime kernel?<br/> <br/> As it can be produced (also for ARM) by applying these patches by Ingo Molnar:<br/> <br/> <URL url="http://www.kernel.org/pub/linu.....ojects/rt/">http...
by selvmarcus
Sun Jan 08, 2012 9:14 am
Forum: General discussion
Topic: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?
Replies: 12
Views: 4647

Re: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?

<r>I just want to add a link for people to learn about latency and how to perform the proper tests.<br/> <br/> I would like to see somebody with a board doing this before the big rollout, so that I and others could decide if it's a viable option for realtime-audio purposes and still get a board on t...
by selvmarcus
Sun Jan 08, 2012 7:53 am
Forum: Staffroom, classroom and projects
Topic: Teaching Real-time Systems
Replies: 14
Views: 6327

Re: Teaching Real-time Systems

<r>One can always hope. I am waiting for about 15 years for some kind of realtime processing (audio) becoming possible on Linux. The kernel is certainly capable of doing  quite well now that for example preemption during system calls is possible (Big Kernel Lock gone), there are realtime scheduler p...
by selvmarcus
Sun Jan 08, 2012 5:21 am
Forum: General discussion
Topic: Raspberry Pi 101 (read before posting)
Replies: 102
Views: 94758

Re: Raspberry Pi 101 (read before posting)

<t>Hello JamesT, you say the numbers are rather good so *you know* , but can you give *us* your rough estimates or are you not allowed to? This really feels a bit strange to me, especially the pseudo-democratic argument that 99.9999% of the people don't need them, don't want them, don't care. So let...
by selvmarcus
Sat Jan 07, 2012 9:17 pm
Forum: General discussion
Topic: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?
Replies: 12
Views: 4647

Re: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?

<r>I looked around and found this which is promising for some experiments.<br/> <br/> <URL url="http://www.opengl.org/sdk/docs.....Pixels.xml">http://www.opengl.org/sdk/docs.....Pixels.xml</URL><br/> <br/> Name<br/> <br/> glReadPixels — read a block of pixels from the frame bufferC<br/> <br/> Specif...
by selvmarcus
Sat Jan 07, 2012 8:40 pm
Forum: General discussion
Topic: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?
Replies: 12
Views: 4647

Re: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?

<t>tufty said: <br/> <br/> <br/> I'm at a real keyboard now, I can expand more easily...<br/> <br/> First off, disclaimer - I don't have a real Pi board.  But I do have the Linux source, which I'm using for development of my own stuff, and have a fair grip on how the Linux - GPU interface works, at ...
by selvmarcus
Sat Jan 07, 2012 8:09 pm
Forum: Other projects
Topic: Down to the metal?
Replies: 10
Views: 2829

Re: Down to the metal?

<t>dom said: <br/> <br/> <br/> dburton said: <br/> <br/> <br/> FB access?<br/> <br/> <br/> The FB access is quite simple. You poke the address of a structure to a mailbox register. The structure defines width/height/bpp etc of framebuffer. The GPU allocates the memory and returns you the address thr...
by selvmarcus
Sat Jan 07, 2012 7:29 pm
Forum: General discussion
Topic: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?
Replies: 12
Views: 4647

Re: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?

<t>Good, thanks for the clarification. I should have done more search before, sorry about that.<br/> <br/> Can you therefore confirm the GPU is not able/ being allowed to render to main memory?<br/> <br/> That's all that what I would ask for at the moment.<br/> <br/> And please if possible some valu...
by selvmarcus
Sat Jan 07, 2012 7:05 pm
Forum: General discussion
Topic: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?
Replies: 12
Views: 4647

Re: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?

<t>Let's hope so, but I am not convinced. I need some tests done by somebody with a board.<br/> <br/> Actually I want to use the GPU, just not for graphics, but audio.<br/> <br/> It would be fine if I can tune it regarding bus consumption by DMA.<br/> <br/> And render to main memory, which I am not ...
by selvmarcus
Sat Jan 07, 2012 5:49 pm
Forum: General discussion
Topic: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?
Replies: 12
Views: 4647

Re: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?

<t>Tomo2k said: <br/> <br/> <br/> The GPU blob is the firmware that runs on the GPU itself. It is the equivalent of the VideoBIOS on your graphics card.<br/> <br/> The ARM only talks to it, it doesn"t run it.<br/> <br/> <br/> I don't think so. The VideoBIOS is located in ROM on the graphics card, bu...
by selvmarcus
Sat Jan 07, 2012 5:00 pm
Forum: General discussion
Topic: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?
Replies: 12
Views: 4647

Re: Latency for realtime USB audio (and GPIO) processing, what is possible? GPU blob=CPU hog?

<t>It should be tested with a recent low-latency enabled kernel.<br/> <br/> It's roundtrip latency what is important, that is from USB audio input (some cheap headset or USB audio class compliant device will do)  through ALSA, jack, ALSA, to USB out. The easiest way to measure it is to plug a microp...

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