[Maarten Tromp] recently took the time to document some of the unusual and creative electronic projects he received as gifts over the years. These gadgets were created in the early 2000’s and still work flawlessly today. Two of our favorites are shown here: Hardware Tetris Unit (shown in the image above) and Heap of Electronic Parts.
Heap of Electronic Parts was a kind of hardware puzzle and certainly lives up to its name. It’s a bunch of parts soldered in a mystifying way to the backs of four old EPROMs — the chips with the little window through which UV is used to erase the contents. Assured that the unit really did have a function, [Maarten] eventually figured out that when placed in sunlight, the device ticks, buzzes, and squeals. [Jeroen] had figured out that the EPROMs could act like tiny solar cells when placed in sunlight, and together the four generate just enough power to drive an oscillator connected to a piezo speaker. It still chirps happily away, even today.
Hardware Tetris Unit was a black box intended to be plugged into a serial port. With a terminal opened using the correct serial port settings, a fully-functional Tetris game using ASCII-art graphics could be played. It was even self-powered from the serial port pins.
Inside Hardware Tetris is an AVR microcontroller with some level shifters, and the source code and schematics are available for download. 14 years later, computers no longer have hardware serial ports but [Maarten] says a USB-to-serial converter worked just fine and the device still functions perfectly.
There are a couple more devices documented on [Maarten]’s gifts page, including a Zork-inspired mini text adventure and a hardware board that does some trippy demos on an old Nokia color LCD. [Maarten]’s friend [Jeroen Domburg] (aka Sprite_tm) had a hand in creating most of the gadgets, and he’s someone whose brilliant work we have had the good fortune to feature many times in the past.
While trying to revive a Donkey Kong Jr arcade board, [Jelmer Bruijn] found himself in the market for an EPROM programmer and became the proud owner of a 1990’s era Dataman S4. Despite its age, it’s a fairly nice tool which allows you to read and write a laundry list of different EPROM types, all without being tied to a computer. The only catch is that a few types of chips need an adapter to work in the Dataman S4, some of which are unsurprisingly no longer available.
After some above and beyond support from the current crew at Dataman set him on the right track, [Jelmer] decided to try his hand at reverse engineering how the old adapters worked so he could build his own. His ultimate goal was to read 40 pin EPROMs on the 32 pin Dataman S4, but in the end he says the information he gathered should be applicable for building other adapters if you ever find yourself in need of such things.
As you might expect, there’s a bit more to the project than a simple pin adapter. [Jelmer] assumed some kind of shift register or latching arrangement would be required to make up for the shortage of pins on the Dataman S4’s ZIF socket. It was just a matter of figuring out how it all went together.
Luckily, [Jelmer] found that the programmer would happily attempt to perform operations on a 16 bit EPROM even though no adapter was physically present. This gave him a chance to probe around with a logic analyzer to figure out what it was trying to accomplish. The trick turned out to be splitting the 16 bit bus into two 8 bit buses which are requested sequentially.
With careful observation, close studying of 16 bit chip datasheets, and much brow furrowing, he was eventually able to come up a design that used five 74xx573 latches and put a schematic together in Eagle. There were a few kinks to iron out when the boards finally arrived, but ultimately the design worked on the first try. [Jelmer] says the same technique should work for 42 pin EPROMs, but as Dataman still actually sell adapters for those he decided not to supply schematics for it.
It all started when I bought a late-1990s synthesizer that needed a firmware upgrade. One could simply pull the ROM chip, ship it off to Yamaha for a free replacement, and swap in the new one — in 2003. Lacking a time machine, a sensible option is to buy a pre-programmed aftermarket EPROM on eBay for $10, and if you just want a single pre-flashed EPROM that’s probably the right way to go. But I wanted an adventure.
Spoiler alert: I did manage to flash a few EPROMs and the RM1X is happily running OS 1.13 and pumping out the jams. That’s not the adventure. The adventure is trying to erase UV-erasable EPROMS.
And that’s how I ended up with a small cardboard fire and a scorched tanning lamp, and why I bought a $5 LED, and why I left EPROMs out in the sun for four days. And why, in the end, I gave up and ordered a $15 EPROM eraser from China. Along the way, I learned a ton about old-school UV-erasable EPROMs, and now I have a stack of obsolete silicon that’s looking for a new project like a hammer looks for a nail — just as soon as that UV eraser arrives in the mail.
We’re all too spoiled nowadays with our comfortable ways to erase and write data to persistent memory, whether it’s our microcontroller’s internal flash or some external EEPROM. Admittedly, those memory technologies aren’t exactly new, but they stem from a time when their predecessors had to bathe under ultraviolet light in order to make space for something new. [Taylor Schweizer] recently came across some of these quartz-window decorated chips, and was curious to find out what is stored in them. Inspired by the BIOS reverse engineering scene in Halt and Catch Fire, he ended up building his own simple reader to display the EPROM’s content.
The 2732 he uses is a standard EPROM with 32kbit memory. Two pins, Chip Enable and Output Enable, serve as main control interface, while 12 address pins select the data stored in the chip’s internal 4K x 8 arrangement, to output it on the 8 data output pins. You could of course hook up the EPROM to a microcontroller and send what you read via serial line, but [Taylor] opted for a more hands-on approach that lets him read out the data in a manual way. He simply uses a bank of DIP switches to set the address and control pins, and added a row of LEDs as display.
Back in the old days, when we were still twiddling bits with magnetized needles, changing the data on an EPROM wasn’t as simple as shoving it in a programmer. These memory chips were erased with UV light shining through a quartz window onto a silicon die. At the time, there were neat little blacklights in a box sold to erase these chips. There’s little need for these chip erasers now, so how do you erase and program a chip these days? Build your own chip eraser using components that would have blown minds back in the 70s.
[Charles] got his hands on an old 2764 EPROM for a project, but this chip had a problem — there was still data on it. Fortunately, old electronics are highly resistant to abuse, so he pulled out the obvious equipment to erase this chip, a 300 watt tanning lamp. This almost burnt down the house, and after a second round of erasing of six hours under the lamp, there were still unerased bits.
Our ability to generate UV light has improved dramatically over the last fifty years, and [Charles] remembered he had an assortment of LEDs, including a few tiny 5mW UV LEDs. Can five milliwatts do what three hundred watts couldn’t? Yes; the LED had the right frequency to flip a bit, and erasing an EPROM is a function of intensity and time. All you really need to do is shine a LED onto a chip for a few hours.
With this vintage chip erased, [Charles] slapped together an EPROM programmer — with a programming voltage of 21V — out of an ATMega and a bench power supply. It eventually worked, allowing [Charles]’ project, a vintage liquid crystal display, to have the right data using vintage-correct parts.
Most video game manufacturers aren’t too keen on homebrew games, or people trying to get more utility out of a video game system than it was designed to have. While some effort is made to keep people from slapping a modchip on an Xbox or from running an emulator for a Playstation, it’s almost completely impossible to stop some of the hardware hacking that is common on older cartridge-based games. The only limit is usually the cost of an EPROM programmer, but [Robson] has that covered now with his Arduino-based SNES EPROM programmer.
Normally this type of hack involves finding any cartridge for the SNES at the lowest possible value, burning an EPROM with the game that you really want, and then swapping the new programmed memory with the one in the worthless cartridge. Even though most programmers are pricey, it’s actually not that difficult to write bits to this type of memory. [Robson] runs us through all of the steps to get an Arduino set up to program these types of memory, and then puts it all together into a Super Nintendo where it looks exactly like the real thing.
If you don’t have an SNES lying around, it’s possible to perform a similar end-around on a Sega Genesis as well. And, if you’re more youthful than those of us that grew up in the 16-bit era, there’s a pretty decent homebrew community that has sprung up around the Nintendo DS and 3DS, too.
Flash memory is the king today. Our microcontrollers have it embedded on the die. Phones, tablets, and computers run from flash. If you need re-writable long term storage, flash is the way to go. It hasn’t always been this way though. Only a few years ago EPROM was the only show in town. EPROM typically is burned out-of-circuit in a programming fixture. When the time comes to erase the EPROM, just pop it under an ultraviolet (UV) bulb for 30 minutes, and you’re ready to go again. The EPROM’s quartz window allows UV light to strike the silicon die, erasing the memory.
The problem arises when you want to use an EPROM for long term storage. EPROM erasers weren’t the only way to blank a chip. The sun will do it in a matter of weeks. Even flourescent light will do it — though it could take years.