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by lb
Thu Sep 06, 2012 6:34 pm
Forum: Debian
Topic: ext4 file system
Replies: 12
Views: 15505

Re: ext4 file system

Generally, there are two types of wear leveling - dynamic and static. Dynamic wear leveling can only distribute wear among blocks that change (that's not ideal for a typical OS installation, since in this case many blocks never change). Static wear leveling makes sure to wear all blocks approximatel...
by lb
Tue Aug 21, 2012 2:30 am
Forum: Networking and servers
Topic: iptables does not close port
Replies: 8
Views: 5903

Re: iptables does not close port

iptables is a beast, but you can somewhat tame it with shorewall.

But seriously, why is there no pf port for Linux yet?
by lb
Thu Aug 16, 2012 8:42 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: ttyAMA0: 1 input overrun(s)
Replies: 17
Views: 9538

Re: ttyAMA0: 1 input overrun(s)

/sys/module/sdhci_bcm2708/parameters/missing_status says N, so the cmdline.txt options works. To make it even worse, I have also errors like Aug 15 13:00:38 raspberrypi kernel: [ 453.642572] mmc0: final write to SD card still running Aug 15 13:00:47 raspberrypi kernel: [ 463.499853] mmc0: Timeout w...
by lb
Thu Aug 16, 2012 8:35 pm
Forum: Deutsch
Topic: Raspberry Ende August bei Vesalia.de?
Replies: 12
Views: 3809

Re: Raspberry Ende August bei Vesalia.de?

Wo ist der Vorteil, wenn du im Supermarkt an der Kasse ein HDMI-Kabel kaufst? Du hast es direkt parat. Naja. Vesalia macht genau solche tollen Lieferversprechen wie Farnell oder RS. Ich würde da nicht meine Hand für ins Feuer legen, dass die Termine eingehalten werden. ;) Und Farnell hat im Moment ...
by lb
Thu Aug 16, 2012 4:15 pm
Forum: Deutsch
Topic: Raspberry Ende August bei Vesalia.de?
Replies: 12
Views: 3809

Re: Raspberry Ende August bei Vesalia.de?

40 EUR plus Versandkosten? Das erscheint mir aber arg teuer! Bei RS und Farnell habe ich inkl. Versandkosten knapp 38 EUR bezahlt, wenn ich mich recht erinnere. Was soll der Vorteil bei Vesalia sein?
by lb
Thu Aug 16, 2012 2:02 pm
Forum: OpenGLES
Topic: Texture Compression
Replies: 29
Views: 5672

Re: Texture Compression

Well, a 2D plane/sprite renderer is really simple to do with ES 2.0, there is none of the somewhat complex transformation math involved, and you can easily apply various effects to the sprites with a fragment shader. ARM's Mali Development Center has some nice examples, including conversion tools. T...
by lb
Thu Aug 16, 2012 10:48 am
Forum: OpenGLES
Topic: Texture Compression
Replies: 29
Views: 5672

Re: Texture Compression

Again, what speaks against the easy solution of using a separate texture for alpha? This uses less than 16 bits per pixel, but provides better quality and full alpha.
by lb
Tue Aug 14, 2012 12:13 pm
Forum: OpenGLES
Topic: Texture Compression
Replies: 29
Views: 5672

Re: Texture Compression

Well, the 4444 format has quite horrible quality... I cannot recommend it at all. What's your use-case?
by lb
Sun Aug 12, 2012 11:32 pm
Forum: OpenGLES
Topic: Texture Compression
Replies: 29
Views: 5672

Re: Texture Compression

For the love of all that is good, please use OpenGL ES 2.0. ETC1 compression is supported. Edit: sorry, I did not notice you want compressed RGB A textures. ETC1 does not support alpha. But you can use an ETC1 compressed RGB8 texture and store alpha in a separate A8 texture. It's easy to combine bot...
by lb
Sat Aug 11, 2012 12:43 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: ttyAMA0: 1 input overrun(s)
Replies: 17
Views: 9538

Re: ttyAMA0: 1 input overrun(s)

Please try to add sdhci-bcm2708.missing_status=0 to cmdline.txt. Unfortunately this won't work well with all SD cards, but it reduces interrupt latency and should avoid the overruns.
by lb
Thu Aug 09, 2012 9:04 pm
Forum: Networking and servers
Topic: sdcard server unrealistic?
Replies: 11
Views: 2805

Re: sdcard server unrealistic?

In my experience, EXT4 is quite reliable with journaling enabled, but the SD card's controller might not deal well with unexpected power outages. However, you can disable journaling with tune2fs, and doing so reduces writes and speeds up operation considerably, possibly at the cost of reliability.
by lb
Tue Aug 07, 2012 1:14 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SMTH08I - I2C kernel module
Replies: 8
Views: 2238

Re: SMTH08I - I2C kernel module

The GPIO on the Pi is definitely NOT 5V tolerant. The examples on that page are potentially dangerous for your Pi!

Use something like this for both SDA and SCL.
by lb
Tue Aug 07, 2012 12:51 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO precision timing (with minimal cost)
Replies: 12
Views: 4480

Re: GPIO precision timing (with minimal cost)

Use a microcontroller. A small Atmel AVR (e.g. Tiny2313) only costs 1-2$ and is up to the job, easy to program and provides a lot of flexibility.
by lb
Mon Aug 06, 2012 7:17 pm
Forum: Graphics programming
Topic: GTK+ Toolkit?
Replies: 23
Views: 14284

Re: GTK+ Toolkit?

I can only recommend to use GTK (with the excellent PyGTK bindings) directly instead. wx is badly designed, badly documented, buggy and a lot of bloat. The Python bindings are a mess, too.

I've used a lot of UI toolkits, and wx is about the worst I've seen yet.
by lb
Sun Aug 05, 2012 1:10 pm
Forum: Troubleshooting
Topic: USB - the Elephant in our Room
Replies: 802
Views: 259979

Re: USB - the Elephant in our Room

Theq FIQ solution seems to be more worthwile. There are other possible sources of interrupt latency than the SDHCI driver, and reducing IRQ overhead is a good thing, too.
by lb
Sun Aug 05, 2012 2:11 am
Forum: Advanced users
Topic: Minimum FAT partition size?
Replies: 9
Views: 5760

Re: Minimum FAT partition size?

CapnBry wrote:A loopback filesystem doesn't make anything smaller
No, but it allows you to workaround partition size issues, and makes installation dead-easy (just copy files with whatever method you have, no image writing necessary).
by lb
Sat Aug 04, 2012 1:54 pm
Forum: Advanced users
Topic: Minimum FAT partition size?
Replies: 9
Views: 5760

Re: Minimum FAT partition size?

I think a loopback filesystem (similar to Ubuntu's WUBI) is the way to go if you want to keep everything as small as possible. But I don't understand your bandwidth issue. Why don't you compress the SD card image?
by lb
Thu Aug 02, 2012 12:59 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: How fast is GPIO??
Replies: 9
Views: 3807

Re: How fast is GPIO??

Carefully written kernel code definitely should be good enough for many tasks that need precise timing, and with interrupts that can be quite efficient. It's probably easier than switching to a real-time OS that is overall badly supported.
by lb
Thu Aug 02, 2012 12:26 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: How fast is GPIO??
Replies: 9
Views: 3807

Re: How fast is GPIO??

GPIOs can be switched at multiple MHz, and that's definitely fast enough. However, you need to write a kernel driver to precisely time GPIO access.
by lb
Tue Jul 31, 2012 11:53 pm
Forum: General discussion
Topic: What's yours called?
Replies: 42
Views: 4433

Re: What's yours called?

raspbian. Very original, I know.
by lb
Tue Jul 31, 2012 11:47 pm
Forum: General discussion
Topic: Overclocking the PI does not work on Raspbian OS? (solved)
Replies: 41
Views: 15837

Re: Overclocking the PI does not work on Raspbian OS? (solve

If you feel adventurous, try this: https://github.com/grigorig/rpi-linux/c ... 3b9d562b2d
If my hunch about this issue is right, this should fix the data loss.
by lb
Tue Jul 31, 2012 10:59 pm
Forum: Troubleshooting
Topic: config.txt reset after reboot
Replies: 11
Views: 14277

Re: config.txt reset after reboot

This is a known bug, probably rooted in the SDHCI driver, and I'm currently investigating it. The FAT filesystem causes single block writes, and these appear to be problematic (i.e. the writes silently don't succeed) with some SD cards. Dataloss bugs are not acceptable. More discussion in http://www...
by lb
Tue Jul 31, 2012 8:20 pm
Forum: General discussion
Topic: Known Problems
Replies: 8
Views: 1137

Re: Known Problems

Well, a few (good quality) SD cards are known to not work, or there are various issues with them (very slow access, or that strange data loss bug on the FAT partition). However, the vast majority of all SD cards work fine now.
by lb
Tue Jul 31, 2012 8:08 pm
Forum: General discussion
Topic: Known Problems
Replies: 8
Views: 1137

Re: Known Problems

The bug tracker doesn't provide a good overview. Generally I'd say these are the typical problems, ordered from major to minor: - Power supply issues (high quality PSU required for stable operation, USB devices that require a lof of power don't work, etc.) - USB issues not related to power supply (h...
by lb
Tue Jul 31, 2012 6:58 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: ttyAMA0: 1 input overrun(s)
Replies: 17
Views: 9538

Re: ttyAMA0: 1 input overrun(s)

This should be the fault of the rtl8192cu driver, it probably momentarily hogs the CPU in some way and that causes buffer overruns with the UART. Workaround: send data to the UART in chunks of <= 8 bytes. ;) Or fix the wifi driver.

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