eeprom

68 Articles

One Bit CPU Runs At A Blistering 60Hz

March 31, 2021 by 20 Comments

If you really think hard about it, a CPU is just a very general-purpose state machine. Well, most CPUs are, anyway. The MC14500 is a one-bit computer that has only 16 instructions and was meant to serve in simple tasks where a big CPU wouldn’t work for space, power, or budget reasons. However, [Laughton] took the idea one step further and created a single-bit computer with no real instructions to control a printing press. The finished machine uses a clever format in an EEPROM to drive an endless program.

Honestly, we’d say this is more of a state machine, but we like the idea of it being a minimal CPU which is also true. The design uses the EEPROM in an odd way. Each CPU address really addresses a block of four bytes. The byte that gets processed depends on the current phase and the status of the one-bit flag register.

Continue reading “One Bit CPU Runs At A Blistering 60Hz” →

Removing Supervisor Passwords And Learning Python

March 24, 2021 by 15 Comments

When learning a new programming language, it’s best to have a goal in mind and work towards it. [Timo] thought it was about time to learn python, and he also had a project in mind: removing the BIOS supervisor password from his old Thinkpad. From there it was just a few keystrokes (and some soldering) and he was able to change the BIOS password of this black box from the outside.

The build utilizes a BeagleBone to communicate with the laptop’s EEPROM via the I2C bus. An oscilloscope also monitors the bus to look for a specific window every four-seconds when the computer is not accessing the bus. During that short period, the EEPROM can be read and written to. Once the window opens, the BeagleBone executes the Python script, which attempts to read the EEPROM and can also perform actions such as removing or changing the BIOS supervisor password.

Of course, tinkering with the EEPROM on a laptop has a high risk of bricking the device, and not all laptops use the same security measures or even memory addresses for things like this, so documentation and precision are key. Also, with Thinkpads of this vintage it’s possible to replace the firmware on these chips entirely with a FOSS version called libreboot, and even though the process is difficult, it’s definitely recommended.

Continue reading “Removing Supervisor Passwords And Learning Python” →

Game Cartridges And The Technology To Make Data Last Forever

December 3, 2020 by 69 Comments

Game cartridges are perhaps the hardiest of all common storage schemes. Short of blunt traumatic force or application of electrical surges to the cartridge’s edge connectors, damaging a game cartridge is hard to do by accident. The same is also true for the data on them, whether one talks about an Atari 2006 cartridge from the late 1970s or a 1990s Nintendo 64 cartridge.

The secret sauce here are mask ROMs (MROM), which are read-only memory chips that literally have the software turned into a hardware memory device. A mask layer unique to each data set is used when metalizing the interconnects during chip fabrication. This means that the data stored on them is as durable as the processor in the game console itself. Yet this is not a technology that we can use in our own hobby projects, and it’s not available for personal long-term data storage due to the costs associated with manufacturing what is essentially a custom chip.

Despite its value as truly persistent storage, MROM has fallen out of favor over the decades. You may be surprised to find a lot of what’s currently used in the consumer market is prone to data corruption over time spans as short as one year to one decade depending on environmental conditions.

So what are we to do if we need to have read-only data that should remain readable for the coming decades?

Continue reading “Game Cartridges And The Technology To Make Data Last Forever” →

Super-Simple VGA Adapter Sports Low-Res Output With Only Four TTL Chips

October 24, 2020 by 20 Comments

Here at Hackaday we cast a wary eye at tips that come in with superlative claims. Generally, if we post something that claims to be the fastest or the smallest of all time, we immediately get slapped down in the comments by someone who has done it faster or smaller. So we present the simplest TTL video card ever knowing the same thing will happen, but eager to see how anyone might scale things down.

To be fair, [George Foot] does qualify his claim to the simplest usable VGA adapter, and he does note that it descends from [Ben Eater]’s “world’s worst video card”, which he uses for his 6502 breadboard computer. But where [Ben]’s VGA adapter uses about 20 TTL chips and an EEPROM, [George] has managed to decrease the BOM to just four TTL chips along with the memory and a crystal oscillator. This required a fair number of compromises, of course; the color depth is fairly low, as is the resolution. Each pixel appears as a thin horizontal bar rather than a small square, leading the images to be smeared out across the screen. They’re still surprisingly viewable, though, which probably says more about the quality of the pattern-recognition wetware between our ears than anything about the quality of the adapter. [George] gives a tour of the circuit in the brief video below.

It looks like [George] has posted a few improvements to the project since we first spotted it, so we’re looking forward to seeing how much the parts count went up. We’re also keen to see if anyone can outdo the simplicity of this effort — be sure to let us know if you give it a shot.

Continue reading “Super-Simple VGA Adapter Sports Low-Res Output With Only Four TTL Chips” →

Glasgow Uses An FPGA As An Embedded Systems Multitool

August 10, 2020 by 13 Comments

Everyone who builds embedded systems wants tools to help build and debug systems faster, so it isn’t uncommon to see boards outfitted with various tools like serial port sniffers. We’ve seen a few incarnations and the latest is Glasgow. The small board uses an FPGA and claims to do the following:

  • UART with automatic baud rate determination
  • SPI or I2C
  • Read and write common EEPROMs and flash chips
  • Read and write common EPROMs including a data rescue function
  • Program AVR chips via SPI
  • Play back JTAG SVF files
  • Debug ARC and some MIPS CPUs
  • Program XC9500LX CPLDs
  • Communicate to several wireless radios and CPUs
  • Do sound synthesis
  • Read raw data from floppy drives

The revC board is the first to be relatively functional and sports 16 I/O pins operating at up to 100 MHz, although the documentation hints that 6 MHz might be the top of what’s easily accomplished. The software is written in Python and the iCE40 FPGA toolchain that we’ve talked about many times in the past.

This already looks like a useful tool and the reconfigurable nature of FPGAs makes it a good platform to expand. The documentation discusses the difficulty in debugging things for the board, so the base software offers support such as a built-in logic analyzer to help.

We have seen dev boards become bench tools, like using the iCEstick as a logic analyzer. It’s nice to see dedicated tools like this one built up around the speed and versatility of FPGAs.

Continue reading “Glasgow Uses An FPGA As An Embedded Systems Multitool” →

The Righteous Quest To Crack A Canon I9900

October 2, 2019 by 34 Comments

[Starhawk] is a man with a problem. More accurately, he’s a man whose mother has a problem, but ultimately that ends up being the same thing. Her wide-format Canon printer recently stopped working after better than a decade of reliable service, and he wants to know why. Rather than spend the money on buying a new printer, he’s determined to find out if she’s been the victim of planned obsolescence by reverse engineering the Canon i9900 to see what makes it tick (or stop ticking, as the case may be).

In the absence of any obvious hardware faults, [Starhawk] has suspicions that the machine’s QY6-0055 printhead has run over some internal “odometer” and simply turned itself off. We’ve all seen similar trickery at play when trying to use third party ink cartridges in our printers, so it’s certainly not outside the realm of possibility that the Canon i9900 is designed to reject heads once they’ve seen enough usage. Perhaps the biggest clue is that the QY6-0055 has a Seiko S93C56BR EEPROM on the board that’s keeping track of…something.

Right now, [Starhawk] is devoting his energies on trying to make sense of the data he pulled from the EEPROM using his TL866A programmer. But that’s no easy feat with a sample size of just one, which is why he’s looking for help. He’s hoping that other hackers with similar printers (and ideally ones that use the same QY6-0055 head) could submit their own EEPROM dumps and the community could get to work trying to decipher what’s stored on the chips. He’s really hoping that somebody at Canon might be willing to sneak him a couple tips on what he should be looking for, but at this point we think he’ll take whatever assistance he can get.

Now to be fair, there’s really no way to know definitively if there’s some flag stored on the EEPROM that’s keeping the printer from working. It could just be good old fashioned hardware failure, which would hardly be a surprise for a piece of consumer electronics from 2005. But even if the effort to understand the Canon’s EEPROM doesn’t get him any closer to a working printer, we still think it’s a fascinating example of real-world reverse engineering that’s worth it for the experience alone.

There’s a long history of hackers doing battle with their printers, from emulating an ink cartridge with a microcontroller to reinking the ribbon of a vintage 1980s behemoth. We’re interested in seeing where this project takes [Starhawk], but no matter what happens there are likely to be some interesting discoveries made along the way.

Logic And EEPROMs Bring VGA To Life, Sans Microcontroller

July 1, 2019 by 9 Comments

For whatever reason, the Video Graphics Array standard seems to attract a lot of hardware hacks. Most of them tend to center around tricking a microcontroller into generating the signals needed to send images to a VGA monitor. We love those hacks, but this one takes a different tack – a microcontroller-free VGA display that uses only simple logic chips and EEPROMs.

When we first spied this project, [PH4Nz] had not yet shared his schematics and code, but has since posted everything on GitHub. His original description was enough to whet our appetite, though. He starts with a 27.175-MHz clock and divides that by 4 with a 74HCT163, which has the effect of expanding the 160×240 pixels image stored in one of the EEPROMs to 640×480. Two 8-bit counters keep track of horizontal and vertical positions, while the other EEPROM takes care of generating the Hsync and Vsync signals. It’s all quite hackish, but it works. [PH4Nz] tells us that the whole thing is in support of a larger project: an 8-bit computer made from logic chips. We’re looking forward to seeing that one too.

This isn’t the first microcontroller-less VGA project we’ve seen, of course. Here’s a similar one also based on EEPROMs, and one with TTL logic chips. And we still love VGA on a microcontroller such as the ESP32; after all, there’s more than one way to hack.

Thanks to [John U] for the tip.