Hacking with Gum got their hands on one of the persistence of vision display fans that Cenzic was giving away at Blackhat this year. It’s not the biggest fan-based POV display we’ve seen but it’s still a fun device to tinker with. They hacked into the EEPROM on the device in order to change the message the fan displayed.

This is very similar to the other EEPROM reading/writing we’ve seen recently. Hacking with Gum read the data off of the EEPROM and then disassembled it to discover how the message data is stored on the chip. This was made easier by noting the messages displayed when the fan is running. The first byte of data shows the number of words in the message, then each chunk of word data is preceded by one byte that represents the number of letters in that work. Data length was calculated based on the number of pixels in each display character. Once he knew the data-storage scheme, it was just a matter of formatting his own messages in the same way and overwriting the chip.

This is a great write-up if you’re looking for a primer on reverse engineering an unknown hardware system. If you had fun trying out our barcode challenges perhaps deciphering EEPROM data from a simple device should be your next quest.

[Thanks James]

Did you forget your hardware-based password and now you’re locked out? If it’s an IBM ThinkPad you may be in luck but it involves a bit more than just removing the backup battery. SoDoItYourself has an article detailing the retrieval of password data from an EEPROM.

The process is a fun one. Disassemble your laptop. Build a serial interface and solder it to the EEPROM chip where the password is stored. Connect this interface to a second computer and use it to dump the data into a file. Download a special program to decipher the dump file and dig through the hex code looking for something that resembles the password. Reassemble your laptop and hope that it worked.

We know that most people won’t be in a position to need a ThinkPad administrator password, but there must be other situations in which reading data off of an EEPROM comes in handy. What have you used this method for?

It started with a simple need: keep tabs on SparkFun Electronics’ in-house kegerator so the beer won’t run out at inopportune times. But of course SparkFun and “simple need” make strange bedfellows…throw beer in the mix, and you know this can’t end well. The result, as you might imagine, reads like a who’s-who of electronics hackery buzzwords.

Arduino? Check. Custom PCB? Check. Web interface? Check. Twitter feed? Check.

They’ve assembled a nice build tutorial on how this all went together, including code, example circuits, an explanation of some of the sensors used, and links to other tutorials for such things as Twittering and persistent storage in EEPROM using Arduino. Not to mention the eye candy: a custom Arduino shield (solder mask and all), custom acrylic tap handle, custom SparkFun pint glasses. They never do anything halfway, do they?

Microchip’s 25AA/25LC EEPROMs are data storage chips with a simple 3-wire interface. The 25AA/LC is an SPI version of the common 24AA/LC I2C EEPROM.  It comes in capacities of 128bytes to 128kilobytes. We looked at the smallest, the 128byte 25AA010A.

There are Bus Pirate demonstrations for most types of serial EEPROMs. Check out our previous 1-wire (DS2431) and I2C (24LC1025) EEPROM posts.

Continue below to see our test circuit and a demonstration of the 25AA010 EEPROM. We used the Bus Pirate to play with this chip from our PC.  For a limited time you can get your own Bus Pirate, fully assembled and shipped worldwide, for only $30.

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Doesn’t look like the Guitar Hero hacks will be slowing up any time soon. In this recent installment, [Thunderhammer3000] built a board to record Guitar Hero “songs”. It is wired inline with with the fret buttons and strum bar and records each of the key presses. Songs can be recorded at slow speed in practice mode and replayed at full speed. The board is Arduino compatible and has two optoisolator chips for collecting the button presses plus a small EEPROM for storage. The board fits easily inside the guitar body.

The 25th Chaos Communication Congress is underway in Berlin. One of the first talks we dropped in on was [script]’s Solar-powering your Geek Gear. While there are quite a few portable solar products on the market, we haven’t seen much in the way of real world experience until now.

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The Maxim DS2431 1K EEPROM is 1-Wire device that adds storage to a project using a single microcontroller pin. We previously interfaced a 1-wire thermometer, but this EEPROM is slightly different because it draws power directly from the 1-Wire bus. Grab the datasheet (PDF) and follow along while we read and write this simple 1-Wire memory.

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This one is fitting – I was just checking out Suunto’s sweet gps data logging watches today. [Steve Cholewiak] sent in his diy GPS data logger. It uses an old DeLorme tripmate – these were serial gps units that ran off of internal batteries. A PIC controller reads the NMEA sentences from the tripmate. Then it stores the track data to an EEPROM. The same serial connection is used to retrieve the data later on. [Steve] did a great job writing this up, the circuit is pretty simple and he’s provided all the information you need to build your own.

A couple years ago I spent a good week wiring up a fairly complex EPROM programmer so I could burn a prom for my jeeps EFI system. Today I ran across this $5 version. build built by Jay Kominek He uses shift registers to handle the addressing and IO lines, all driven directly by the parallel port. There’s no way to escape the number of pins that have to be wired up, but the schematic itself is pretty simple.
[By the way, arcade supply shops are a great source for cheap UV erase EPROMS.]

[Update: I'd forgotten about the voltage change (3 vs 5 if I remember) needed to write UV EPROMS vs EEPROMS. With a little mod, you can certainly use this for EPROMS as well.]