Single Board Revolution: Preventing Flash Memory Corruption

An SD card is surely not an enterprise grade storage solution, but single board computers also aren’t just toys anymore. You find them in applications far beyond the educational purpose they have emerged from, and the line between non-critical and critical applications keeps getting blurred.

Laundry notification hacks and arcade machines fail without causing harm. But how about electronic access control, or an automatic pet feeder? Would you rely on the data integrity of a plain micro SD card stuffed into a single board computer to keep your pet fed when you’re on vacation and you back in afterward? After all, SD card corruption is a well-discussed topic in the Raspberry Pi community. What can we do to keep our favorite single board computers from failing at random, and is there a better solution to the problem of storage than a stack of SD cards?

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Transcend Wifi SD Card Is A Tiny Linux Server

[jamesone111] bought a Transcend WifiSD card, presumably for photography, but it may just have been because he heard that they’re actually tiny Linux servers.

He read a post about these cards on the OpenWRT forums. They’re all a similar configuration of a relatively large amount of memory (compared to the usual embedded computer), a WiFi chip, and an ARM processor running a tiny Linux install. The card acts as a WiFi access point with a little server running on it, and waits for the user to connect to it via a website. It also has a mode where it will connect to up to three access points specified by the user, but it doesn’t actually have a way to tell the user what its IP address is; which is kind of funny.

[jamesone111] hacked around with the Transcend card for a bit. He found it pretty insecure, which as long as you’re not a naked celebrity, shouldn’t be a huge issue. For the hacker this is great as it opens up the chance of hacking the firmware for other uses.

Some have already pulled off some cool hacks with these cards. For example, [peterburk] hacked a similar card by PQI to turn his iPod into a portable file server. 

Floppy Drive Hides SD Card Reader

[gilmour509] posted a thorough gallery of a new custom-built computer and case made to look like a 1995 IBM Aptiva. While the whole build is impressive, the most clever part involves a 3 1/2″ floppy disk that hides an SD card and works like a regular USB flash drive when inserted into the floppy drive.

He makes use of the fact that floppy disk edge card connectors have the same spacing as SD cards. Add in a hacked USB card reader, some careful cutting and assembly, and [gilmour509] has a very convincing floppy drive with gigabytes of space.

When inserted the light turns on and windows recognizes the drive.

The best part is that with everything put together, the floppy disks and floppy drive look completely unmodified. He even made the file explorer icon show a floppy drive.

The faux-Aptiva gallery includes the full build, but skip to about 2/3 down to see the floppy SD card section.

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Hackaday Prize Entry: An SD Card Arduino

About a year ago, Intel announced they’d be launching a new platform stuffed into an SD card. Imagine – an entire computer packaged into an SD card, with nine whole pins for power and I/O. Cooler heads prevailed, the Intel Edison was launched, but the idea stuck; why can’t you fit an Arduino in an SD card?

[kodera2t] found out there’s no real reason why you can’t put a small microcontroller inside an SD card. For his Hackaday Prize entry, he created the SDuino, and it’s exactly what it says on the tin: an ATMega328p stuffed into a microSD adapter.

Unlike the other microcontroller stuffed in an SD card platform — the Electric Imp, [kodera] is, for the most part, respecting the standard pinout for SD cards. The MISO and MOSI signals are reversed, of course, one of the grounds on the SD pinout is tied to an analog input pin on the microcontroller, and the chip select on the SD pinout is ignored completely. Other than that, it’s the closest you’re going to get to an SD card with a microcontroller.


The 2015 Hackaday Prize is sponsored by:

Manual Data Recovery With A Hex Editor

Let’s say you use an SD card-base portable audio recorder for work – doing an interview, perhaps. Things go well until one day, you turn the recorder off before stopping the recording. Without pressing that big red Stop button, the file doesn’t close, and you’re left with a very large 0kB file on the SD card. How do you get it back?  There are tools that will do it for you, but they cost money. You can do it yourself with a hex editor, though, and it’s actually pretty easy.

The software required for this feat of data recovery is Roadkil’s Disk Imager to dump all the bits on the SD card to an image file, the free version of ISO Buster to show the block addresses and length of each file, and the hex editor of your choice. The process starts as simply an experiment for hot to create an MP3 file by cutting and pasting bits into a hex editor. A good file was found in the hex editor, copied to a new file, and played. Everything works so far; great.

For the actual data recovery, a spreadsheet was created to make an educated guess as to where the lost file should be. Starting at this address, about 90MB of data was copied into a new hex editor window. This is where the recovery hit a snag. Because the SD card was plugged into a Mac before, a bunch of data was written on the card. This went into the first available place on the disk, which just happened to be the header of the lost MP3 file.

That’s not a problem; there’s already the header from an MP3 file sitting in a hex editor from the first experiment to see if this was possible. By copying a few hundred bytes to the front of the lost file, the file was corrected just enough that an MP3 player could reconstruct the file.

It’s not perfect – the first fifty seconds of the interview was garbled. The rest of the interview was saved, though, and that’s much better than losing the entire thing. Thanks [Lewin] for sending this one in.

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File Sharing In Your Pocket

The idea of a pirate box is pretty simple. All you need is a tiny Linux system with a WiFi adapter, a bit of storage space, and the software that will allow anyone to upload a few files to the server and an interface that will let anyone on the network download those files. In practice, though, a pirate box is a mess of wires and power adapters – not the pocketable device a WiFi file sharing box should be.

[Chris] came up with a much smaller file sharing beacon. It’s not based on a router; instead, [Chris]’ build uses an ez Share WiFi microSD adapter. It’s a device meant to push pics taken by a digital camera up to the Internet, but by configuring the software just so, up to five users can connect to the adapter and pull files down from a microSD card. The build only requires putting power to the correct pins. A LiPo battery and charge controller takes care of this problem.

There are a few shortcomings to this project – [Chris] doesn’t know how to upload files to the device. Maybe someone sufficiently clever can figure out how to make that work. Still, if you’re ever in a situation where you’d like to share some files with people in the same building, this is the device you need.

Thanks [Jake] for the tip.

Raspberry Pi Backup Scripts

Raspberry Pi

[Matthew’s] recent blog post does a good job explaining the basics of the Raspberry Pi’s file system. The Linux operating system installed on a Pi is generally installed on two different partitions on an SD card. The first partition is a small FAT partition. All of the files on this partition are used for the initial booting of the Pi. This partition also includes the kernel images. The second partition is the root file system and is generally formatted as ext4. This partition contains the rest of the operating system, user files, installed programs, etc.

With that in mind you can deduce that in order to backup your Pi, all you really need to do is backup all of these files. [Matt] has written some scripts to make this a piece of cake (or pie). The first script will simply copy all of the files into a gzipped archive. You can save this to an external SD card, USB drive, or network share.

The second script is perhaps more interesting. This script requires that you have one free USB port and a USB SD card reader. The script will automatically format the extra SD card to contain the two critical partitions. It will then copy the “boot” files to the new boot partition and the root file system files to the new SD card’s root partition. When all is said and done, you will end up with an SD card that is an exact copy of your current running file system.

This can be very handy if you have multiple Pi’s that you want to run the same software, such as in a Pi cluster. Another good example is if you have spent a lot of time tweaking your Pi installation and you want to make a copy for a friend. Of course there are many ways to skin this cat, but it’s always fun to see something custom-built by a creative hacker.