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by dms75
Tue Feb 05, 2013 4:06 pm
Forum: General discussion
Topic: Can you brick a Pi?
Replies: 14
Views: 5440

Re: Can you brick a Pi?

Burngate wrote: There's got to be a kid someplace that'll think it fun to try
At least from an educational point of view that kid will have acquired a lot of usefull skills for an embedded systems engineer ;-)

Dirk
by dms75
Tue Feb 05, 2013 2:15 pm
Forum: General discussion
Topic: Can you brick a Pi?
Replies: 14
Views: 5440

Re: Can you brick a Pi?

The chances of bricking the Rpi with overclocking are rather low I'd wager, most likely you'd just reduce it's lifespan, so accidentially bricking the RPi with software would be very hard. (Has anyone tried to disable the overcurrent protection, to overvolt and overclock such that it doesn't just cr...
by dms75
Wed Jan 16, 2013 1:49 pm
Forum: Advanced users
Topic: Boot with SD readonly?
Replies: 36
Views: 24630

Re: Boot with SD readonly?

Hi I just sent you the needed spi command sequences to initialize and writeprotect a sdcard by setting the writeprotectbits in the CSD Register via a pm. You can use this sequence if you connect the sdcard to the raspberry pi gpio header SPI Pins or with an external microcontroller board, wichever s...
by dms75
Sat Dec 29, 2012 9:16 pm
Forum: Troubleshooting
Topic: Raspberry Pi won't boot if GPIO SCL is pulled down
Replies: 1
Views: 692

Re: Raspberry Pi won't boot if GPIO SCL is pulled down

Hi, The SCL Pin pulled down will force the bootloader into safe mode where it will load kernel_emergency.img along with ignoring config.txt and applying a default cmdline.txt. If no kernel_emergency.img exists kernel.img will be loaded. This behaviour is intended to allow recovery from overclocking ...
by dms75
Mon Dec 10, 2012 7:36 am
Forum: General discussion
Topic: ext3/4 and SD-card wear leveling
Replies: 134
Views: 56598

Re: ext3/4 and SD-card wear leveling

Hi To add some information regarding the behaviour of SDHC cards, all the sandisk SDHC cards I have come accross almost imediately return from a block erase command, after wich the block is reread as zero. Writing Zeroes to that block actually is much slower, so I guess that the erase command only m...
by dms75
Tue Nov 13, 2012 8:01 am
Forum: Graphics programming
Topic: Qt on Raspberry Pi as an Embedded System
Replies: 10
Views: 11382

Re: Qt on Raspberry Pi as an Embedded System

Hi, as a lower bound for linux-ish boot times that can be achieved I tested the following setup: - booting overclocked to 1 GHz - a fast class 6 SDCARD Sandisk 30MB/s for fast 4k block access times - initial turbo - loading the emergency_kernel with a small custom initramfs specified in the config.t...
by dms75
Mon Nov 12, 2012 7:38 am
Forum: Graphics programming
Topic: Wayland Progress
Replies: 4
Views: 3098

Re: Wayland Progress

Hi,

great work! Can you tell me whether the Mer project uses hardfloat of softfloat on the raspberry?

Dirk
by dms75
Mon Oct 29, 2012 1:04 pm
Forum: Raspbian
Topic: Status on new version of Raspbian?
Replies: 6
Views: 1612

Re: Status on new version of Raspbian?

Any chance for the new snapshot to contain a relatively stable qt5 "nightly" as was discussed on the qt mailing list some time ago?

Dirk
by dms75
Wed Oct 24, 2012 1:48 pm
Forum: Advanced users
Topic: Boot with SD readonly?
Replies: 36
Views: 24630

Re: Boot with SD readonly?

So basically this whole idea is wrong. It is the operating system that needs to support not writing to the card. You cannot try to impose the restriction upwards from the hardware. I totally agree that for itself it would not be very usefull. Setting up the whole system with a initrd and ro mount o...
by dms75
Wed Oct 24, 2012 1:00 pm
Forum: Advanced users
Topic: Boot with SD readonly?
Replies: 36
Views: 24630

Re: Boot with SD readonly?

Such a straight forward feature would be hugely appealing to the embedded market. The proper way to do it would probably be an extension to the kernel sdcard driver that could be used in the manner of "echo 1 > /sys/class/mmc_host/mmc0/mmc*/temporary_writeprotect" That would allow to set and to uns...
by dms75
Wed Oct 24, 2012 10:02 am
Forum: Advanced users
Topic: Boot with SD readonly?
Replies: 36
Views: 24630

Re: Boot with SD readonly?

Is there some way of physically write protecting the SD card, insuring that the raspberry pi cannot write to it? Not in hardware, presumably a firmware change would be required to prevent all writes to SD card (hmmm, wonder if Dom would consider adding a cmdline.txt/config.txt option to disable SD ...
by dms75
Wed Oct 24, 2012 8:54 am
Forum: Advanced users
Topic: Boot with SD readonly?
Replies: 36
Views: 24630

Re: Boot with SD readonly?

Hi, since I have used sdcards in several microcontroller related projects, I might as well give some hints how it could be done. In theory you can set the write protect Bits in the CSD register of the sdcard. Accessing them on the Pi is not quite so easy though. First those writeprotect-bits are pro...
by dms75
Fri Sep 21, 2012 8:45 pm
Forum: Advanced users
Topic: Overclocking
Replies: 1125
Views: 600658

Re: Overclocking

I rather don't think it's the power supply, because for those tests i had my rpi connected to an Agilent Lab-powersupply capable of 20A at 5V (current limit set to 1500mA) and I'm powering via the GPIO header, so there is no polyfuse in the supplychain either. The current consumption (Pi + keyboard ...
by dms75
Fri Sep 21, 2012 2:35 pm
Forum: Advanced users
Topic: Overclocking
Replies: 1125
Views: 600658

Re: Overclocking

It seems i have a very overcurrent sensitive pi. I managed to get it stable (Quake3 stable) with 950 arm core 250 sdram 400 overvolt 2 With anything more overvolt or frequencies i get resets under Quake3. Without any overvolting i can still reach arm 900 core 333 sdram 500 which is probably better f...
by dms75
Fri Sep 21, 2012 8:14 am
Forum: Advanced users
Topic: Overclocking
Replies: 1125
Views: 600658

Re: Overclocking

Is there any specific reason for the overcurrent protection to issue a reboot instead of just falling back to the default clock values like the thermal protection does? I could imagine that it might be a hardware block only capable of doing a reset wich can be disabled, but if it is managed by the f...
by dms75
Thu Sep 20, 2012 2:15 pm
Forum: Advanced users
Topic: Overclocking
Replies: 1125
Views: 600658

Re: Overclocking

Hi, I think i might have found a bug or more likely an error in the documentation. I have set the following values: arm_freq=950 core_freq=374 sdram_freq=500 over_voltage=2 when idle it runs happily at arm 700, core 250 but when in turbo mode when i enter cat /dev/urandom | bzip2 > /dev/null & the a...
by dms75
Sat Sep 01, 2012 9:00 am
Forum: General discussion
Topic: USB Device Overwrites SD Card (permanently)
Replies: 19
Views: 5473

Re: USB Device Overwrites SD Card (permanently)

Well, since it seems to be narrowed down to a powersupply related problem reading the sdcards CSD register will only serve in determining wether the card can be recovered or not, and of course to satisfy our curiosity. The time spent to read the CSD register might not be worth the cost of the cards,...
by dms75
Thu Aug 30, 2012 3:48 pm
Forum: General discussion
Topic: USB Device Overwrites SD Card (permanently)
Replies: 19
Views: 5473

Re: USB Device Overwrites SD Card (permanently)

After some searching through the forums I found that the official raspbian net installer comes with a initramfs and you can open a new terminal with [Alt]+F2 or [Alt]+F3. Since this installer will download and write stuff to your sdcard it obviously has the required Kernelmodules for the sdcard inte...
by dms75
Thu Aug 30, 2012 11:43 am
Forum: General discussion
Topic: USB Device Overwrites SD Card (permanently)
Replies: 19
Views: 5473

Re: USB Device Overwrites SD Card (permanently)

Without further hardware it might be possible to boot a kernel with a small initramfs form a working SDCARD. After booting you could remove the SDCARD, unload the SDCARD driver and insert the not working one. After reloading the SDCARD driver it should be possible to have a look at the CSD register ...
by dms75
Thu Aug 30, 2012 9:51 am
Forum: General discussion
Topic: USB Device Overwrites SD Card (permanently)
Replies: 19
Views: 5473

Re: USB Device Overwrites SD Card (permanently)

If the RPi would care about the lock switch... It is in the responsibility of the SDCARD-reader to check for the lock swich (The card itself cannot sense its position) and afaik the SDCARD-slot on the RPi cannot sense the lock switch position either because that signal is not connected. Edit: The fo...
by dms75
Thu Aug 30, 2012 9:43 am
Forum: General discussion
Topic: USB Device Overwrites SD Card (permanently)
Replies: 19
Views: 5473

Re: USB Device Overwrites SD Card (permanently)

Hi, From The SDCARD Spec (the non simplified old one V1.9 after that they only published simplified specs wich left out timing information and writeprotection information: "1.5.9.10. Write Protection Two-card level write protection options are available: permanent and temporary. Both can be set usin...
by dms75
Thu Aug 23, 2012 10:52 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Raspberry Pi + Arduino + SPI
Replies: 19
Views: 7761

Re: Raspberry Pi + Arduino + SPI

Hi,

Surely you meant to say 1k1 for the top resistor and 2k2 for the bottom resistor so accross the bottom resistor you'd have 2/3 of the total resistance (2k2 of 3k3) and equally 2/3 of the total voltage (3.33V of 5V). ;)

Dirk
by dms75
Thu Aug 23, 2012 8:42 pm
Forum: Raspbian
Topic: building qt5 on the board itself
Replies: 5
Views: 8040

Re: building qt5 on the board itself

Hi, I had a simmillar problem when crosscompiling qt5 (crosscompiling since I am still waiting for my Pi... why on earth did i order at RS.... ) in the qtbase directory type git branch If it shows this: * (no branch) master Then you must checkout to master branch before running ./configure. To do so...
by dms75
Thu Aug 16, 2012 11:30 am
Forum: General discussion
Topic: A plea to the Foundation re. MPEG-2
Replies: 153
Views: 43347

Re: A plea to the Foundation re. MPEG-2

Edit: this reply was to a quite old post in this thread to someone claiming the end user would have to pay license fees for using software codecs. The answer is - you don't need to, actually the reason is quite simple: Patent fees have to be paid if you use the patented technology commercially. If y...
by dms75
Sun Aug 12, 2012 11:12 am
Forum: General programming discussion
Topic: SD locked on RasPi
Replies: 4
Views: 1657

Re: SD locked on RasPi

Refering to appoach 2: You could set up as system which uses an initramfs which decrypts the linux root filesystem with the PI Hardware serial Number for example. This would help in the case where somebody steals a working SD-Card, but not the corresponding RPi. Anyone with a working combination of ...

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