Archive for August, 2008

Compact Flash Linux Computer

C-Data Solutions has a mini computer the size of a Compact Flash card.  Yes, that’s right.  The form factor of this Linux computer is that of a Compact Flash card.  The solution uses a CF DAQ card as the main processor and you can expand for additional flexibility using the CF COMM cards.

CF linux computer

The Compact Flash Computer utilizes Motorola’s Coldfire MFC5272 processor. The on-board flash memory file system provides storage for the operating system (ucLinux) and user applications. Expansion is via a 16 bit bus compatible with Compact Flash devices. Up to eight devices can be integrate into a system using the Bus Extension Unit (CF type II device). Here are the impressive specifications to the CF Linux computer:
  • 43 x 37 x 5 mm
  • Compact Flash Type II Card
  • 16 Bit CF expansion bus Interfaces to CF cards
  • 32 bit Coldfire cpu
  • 32 MB SRAM
  • 8 MB FLASH
  • µcLinux
  • RS-232
  • Motorola BDM port
For more information visit the C-Data Solutions website.  Source via Hacker-Technology. Continue Reading 6 Comments

Why Is My SD Card Write Protected?

I ran into a situation the other day where my SD card was [all-of-a-sudden] write protected. I couldn’t format it, I couldn’t delete the files and I certainly couldn’t write to it. I checked the lock/unlock switch and still, no avail. I thought the card was a total loss.

It turns out, the SD card wasn’t the problem but the card reader was.

After some internet searching I found several solutions to the problem, but no one really explained what the problem was. So I thought others could learn on “why” their SD card was write protected and giving problems.

First off, lets take a look at the SD card reader itself. Below is a typical SD connector found inside most SD card readers. The area I will be talking about today is the part of the reader which makes a physical connection to either give write access or provide write protection. It’s the thin metal strip the blue arrow is pointing to.

internal sd card reader

What gives the SD card write protect error is when that metal strip does not make contact with another metal strip on the inside of the card reader. When the SD flash memory card is pushed inside the card reader, the internal metal strip is pushed outward and makes contact with the outer metal strip shown in the picture above.

To give you a better idea, here is a rough drawing / schematic of the metal connectors:

sd write protect

The interal piece has an angle to the shape so when the SD card is inserted the metal strip gets pushed outward making contact with the outer metal piece. This shorts the circuit and provides access to the SD card. Here is another lovely example which might help make my point:

sd write protect off

The problem occurs when those two metal pieces don’t make contact when the SD card is inserted in the SD card reader. This is where you get the SD write protect error. Typically the internal piece gets damaged because the SD card was pushed in too hard or too fast and the internal metal piece was damaged. The damage would be either the metal angle getting bent flat or pushed deeper into the card reader.

Here are several solutions to resolve the write protect error for the SD media.

1) Put a piece of tape on the SD card – the side where the lock/unlock mechanism is. This will generally push the internal metal piece back out enough to make contact with the outer metal strip. Thus resolving your issue. This is the easiest solution because it doesn’t require opening the SD card reader.

2) A more permanent solution would be super-glue the two metal pieces together so contact is always made. Using a paper-clip or small pin, you can push the internal metal strip out toward the external piece to make contact; then glue the two together. Liquid super-glue works extremely well with metals and should stick immediately.

sd card read error

If the internal metal piece is pushed back into the card reader, it might be difficult to glue the two pieces together. It might also be damaged enough that tape doesn’t help. In that case, buy a new SD card reader…after all, they are only a couple bucks these days.

The point to all of this, isn’t the fact that SD card readers are cheap, but your SD flash memory isn’t write protected like you originally thought.  So don’t throw good SD memory away – just try one of the two methods above and I bet your problem will be resolved.

As a side talking point; if you are trying to set write protection for an SD card this is something which must be done at the device level. So the card reader isn’t related to an official write protect SD Card. To _create_ a write protect SD card then a specific vendor command must be sent to the controller on the memory card which blocks the write sequence. There is equipment with this capability such as Nexcopy’s SD Card Duplicator.

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