In a show of solidarity with our oppressed Meleagris gallopavo brethren, there will be no craft night this Thursday, November 28th. We recommend gathering together with friends and loved ones and sharing a hearty seasonal meal of kale and pine nuts instead. See you all next week!
Some technologies are so direct and intuitive that they feel classic even when they’re new. Some technologies are so ahead of their time that they only find their true purpose years after they’ve been put out to pasture.
In the early 80′s, France Telecom rolled out the Minitel, a videotex system offering various online services to users across France. Subscribers were given small, semi-portable CRT-based terminals. The service was a success, and at its peak boasted 25 million users. But eventually, well, you know. The internet. In June 2012, France Telecom finally pulled the plug on the Minitel. Screens across the country went dark. Millions of little, boxy terminals, suddenly cast adrift. Widespread technology, lost and alone, in search of purpose. Purpose now, suddenly, found.
The Minitel/Tumblr Time Tunnel is a Minitel 1B US (yes, there was a QWERTY version) backed by a Raspberry Pi. Enter a few tags at the prompt, and the mighty firehose of Tumblr will be unleashed upon your tiny, 3-bit
(The asterisk after “3-bit” is due to the fact that each 2×3 block of “pixels” is actually a single character with foreground and background color attributes, so each 2×3 block only has one bit of color data, selected from a palette of 8 colors.)
As is de rigueur, all the code is available on github.
The Minitel/Tumblr Time Tunnels will be on display at this year’s NYCR Interactive Party. Be sure to come by and see the internet the way it positively demands to be seen!
Rapid prototyping tools are great for quick hacks, but their real power lies in their ability to allow you to quickly iterate and refine a design. Earlier this week I hacked together a primitive nine-channel punched paper tape reader, but it had a number of limitations: the LEDs that I was using to read the bits were noisy and slow, the materials used didn’t mask the light well enough, the tape wasn’t mechanically aligned well, the electronics were a mess and the entire mechanism was difficult to use. This Friday, I decided to do what my third-grade teacher would tell me to do every time I half-assed something: go back and do it right.
This time I used proper phototransistors and IR LEDs I scrounged up around the space (thanks, Miria and Raphael!). Because they’re 5mm in diameter (and the spacing between channels is only 2.54mm), I had to come up with a new sensor packing. This one reads bits from four separate columns over a space of five columns, requiring an internal buffer of five columns to reconstruct a single column of data. Even so, the spacing was tight, and I had to sand down the flanges of the phototransistors and LEDs to make everything fit. I milled simple PCBs for both sides to keep things nice and neat, and used a small surface-mount potentiometer to limit the current to the LEDs in case the paper wasn’t thick enough to block enough light. The light mask is made of black acetal this time, and the spacers include runners to help keep the tape straight. There’s still no automatic feed mechanism, but we now have a reader that’s fast and reliable enough to read tapes in earnest.
The updated code, mechanical drawings, and PCB designs are all up on Github. There are still a few tweaks we’d want if we were going to scan more tapes, but this version works very well. Now we just have to figure out what to do with all these PDP-8 binaries. Any ideas?
(Note to time-travelling computer conservators: in the past/future, please do not store your paper tapes in damp basements. These programs are stinky. The Fortran compiler, in particular, is exceptionally foul. Yours truly, phooky.)
Trammell came across a cache of punched paper tape recently. My immediate impulse was to create the most primitive tape reader possible. Thusly:
The rig is composed of a Teensy++ 2.0, eighteen red LEDs, eighteen resistors, and a few bits of laser-cut plastic. LEDs are used to both illuminate the paper and sense the holes. The sensor design is based on the classic Arduino LED sensing code. It’s not very reliable, but it’s a fun afternoon proof-of-concept.
If you’re interested, the code and design files are up on github.
So, once in a while, I wake up feverish in the middle of the night, screaming “CLAMPS! I NEED MORE CLAMPS!” Oh, you too, huh?
It’s your lucky day! Or rather, this coming Sunday, April 7th is your lucky day, when NYCR and our good friends at the Industry City Distillery will be having our first-ever garage sale. We’ll be selling all kinds of hardware oddities, including:
- Hand tools!
- Power tools!
- Strange, unidentifiable tools meant for neither hand nor eye!
- Microscopes! Boroscopes!
- Audio equipment! Video equipment! Audiovisual equipment!
- Files! Floppy diskettes! Raw steel! Cooked steel!
- A vertical mill! (U-buy, U-move!)
- Electronic bits! Non-electronic bits!
- More VHS recorders than you’re prepared to buy!
- aaannnddd moooooorrrreeee!!!
We’ll be having the sale in beautiful Industry City, Brooklyn, in association with the Industry City Distillery, manufacturers of incredible spirits. Come by to buy! Come by to browse! Come by to meet amazing people!
The sale starts at 11:30 AM, Sunday, April 7th and continues until sunset, at which point we’ll just start calling it a party. The address is 33 35th Street, Brooklyn, NY, just two blocks downhill from the 36th Street Station on the D, N, and R trains. It’s just one stop on the N train from NYCR.
See y’all Sunday!
These are seven layers of a backlight from an old laptop LCD. The amount of optical engineering required to produce a nice, even glow from an edge-lit panel is impressive.
(Be careful if you’re taking one apart yourself– until recently many LCDs were backlit by CCFLs, which contain a small amount of mercury and need to be disposed of properly.)
As midnight approached this New Year’s Eve– as champagne bubbled from uncorked necks and we all prepared for the coming year in various postures of revelry or bleak resignation– I grappled silently with the pivotal question of our time: “How awesome are robots?” The answer is of course that robots are completely awesome. That settled, I resolved to build one robot a month for the duration of 2013.
Much to the chagrin of Brooklyn’s legion of artisanal slow-cooking egg-boilers, January’s robot is a an automaton for preparing soft-boiled eggs for human consumption.
This was a junkbot, assembled from various scraps that have ended up in the space over the years. Expert junkspotters will note:
- The heating element and thermistor from a trashed mini-espresso machine
- One 250mL beaker of questionable provenance
- Some off-brand extruded aluminum
- Skate bearings
- A haunted steel counterweight
- Lots of lasercut acrylic and delrin
- Some chunks of 4×4 sliced out of the loft supports from the original NYCR location
- A couple of analog servos and a DC motor from the junk drawer
- One half of a L298 from a driver board I designed in 2005
- Some relays from sharesville
- A button from a reflow oven
- Random bolts, plywood, etc.
The whole shebang was controlled by a Teensy 2.0 and powered from a bench supply (except the heating element which was run off of 120VAC, which is why the lights keep dimming during the video).
All the code and CAD files are in my Github repo, as usual. Special thanks to Charles Pax for donating the boiler from his busted coffeemaker, Eric Skiff for providing the tunes for the video, Nick Farr for a last-minute game-changing special Club Mate delivery, and everyone at NYCR for indulging my little robot habit.
A quick reminder– there’s no craft night this Thursday, November 22nd, due to ectoplasmic containment issues corresponding to an influx of angry turkey ghosts. Happy Thanksgiving!
Heading to Toorcamp? Take a second to cast around your hackerspace, workshop, or trash heap and grab any interesting-looking ROMs you come across (or just any sufficiently interesting/old PCBs). I’ll be there with one of Trammell’s incredible super-tiny readers, a soldering iron, and unfathomable patience to help you perform some digital archaeology and light necromancy.
Dump your ROMs!
Last week I posted a screed about that peculiarly modern variant of grave-robbing, ROM-dumping. That was the Why; this post is the How.
Dumping the contents of a ROM onto your computer is surprisingly simple. All you need to get started is:
- An Arduino Mega or similar board 1 (you’ll need at least 24 I/O pins).
- A breadboard
- An EPROM to read
- Some wires and a wire stripper
- Your wits 2
That’s all. Gather your materials and let’s get cracking!
Step negative one: What are ROMs for?
ROM is an old term for “Read-Only Memory”. Nowadays these chips are often more correctly referred to as “non-volatile memory”, but it boils down to the same thing: they’re chips that store data even after you unplug your computer. When a digital device turns on, it effectively has amnesia. The only information it has about the world is what’s stored on its ROMs. So the first thing many devices do when they wake up is start reading instructions from a ROM. It’s like Guy Pearce’s tattoos 3 for your computer.
Step zero: Find a board with a brain.
Almost any board of a certain age 4 which has a digital processor is likely to have a ROM of some sort on it. The easiest way to figure out whether there’s an interesting ROM on a board is to take it out and start hunting! Here’s a pile of boards from our scrap bin that are likely candidates. Let’s see what we can dig up.
Step one: Find your ROMs.
There are many types of ROM out there, but today we’ll be hunting for EPROMs. EPROM stands for “erasable programmable ROM”. 5 They look like this:
EPROMs are erased by exposing the chip to ultraviolet light, which is why they have that distinctive quartz window you see above. However, in general it’s a bad idea to leave the window exposed like this, since over time stray UV will start to erase random bits. That’s why most EPROMs you come across will have a label over the window, like this:
Both of the labelled chips here are EPROMs. You’ll also notice that EPROMs are almost always in sockets, rather than being soldered directly to the board. This is so the data in the ROMs can be easily written or updated after the circuit boards are manufactured, and so devices can be patched or upgraded in the field. Of course, it also makes them easy for us to remove!
Another popular type of ROM is the “masked ROM”. These are true read-only memories; the data is etched on to the chip at the time they are manufactured 6 and can not be erased or updated. Because they aren’t reprogrammable, they don’t have clear windows, and usually don’t have labels. Here’s the mainboard from a Commodore 64; can you spot the ROMs?
As you can see, it’s difficult to distinguish a masked ROM from any other chip. Because they are manufactured in large quantities, they are usually silkscreened with a custom part number, and because sockets are expensive in mass-produced hardware, the chips are often soldered directly into the board. There’s only one reliable way to determine which chips are the ROMs. This is a picture of the same board taken at midnight:
It’s pretty clear which chips are the ROMs now, right? The low green phosphorescence you can see in this image appears at the witching hour due to the fact that almost all masked ROMs are haunted 7. If for some reason you can’t stay up that late to identify the ROMs, 8 you can try to use a schematic to find them. 9
Masked ROMs are clearly bad juju. Let’s stick with EPROMs.
Step two: Prepare and remove the chip.
Next, if there’s no label over the window on your EPROM, you’ll want to cover it up as soon as you can. Electrical tape works well for this. Cut a small piece and make sure the entire window is covered, as below.
You can easily pry a chip out of its socket with a flathead screwdriver. Be gentle and patient! It’s important not to bend any of the pins. Pry slowly from one side, and then the other.
If you do bend any of the pins, use some pliers to carefully straighten them out.
Step three: Identify the chip.
Now that you’ve got your ROM, the next step is to figure out exactly what sort of chip you’ve got. Read the silkscreened part number on the top of the chip. You may need to partially remove the label to see the entire part number; just be sure to keep the window covered (or cover it again with some tape once you’ve figured out the part number).
The part number is usually the topmost silkscreened text on the chip. Often you’ll see a part number that contains “27C”; this is one of the most popular types of EPROM. The chips above are all either 27C256 or 27C512 parts. The last three digits of the part numbers above– 256 and 512– represent the amount of data the chips can store in kilobits. That’s kilobits, not kilobytes, so you’ll have to divide by eight to figure out how many kilobytes the chips can store. For example, the 27C256 can store 32 kB of data.
Also, don’t forget to record any identifying information you find on the label or board! Having a pile of data is of no use if you don’t remember where it came from.
Step four: Figure out which pin is which.
EPROMs operate in a straightforward fashion. Internally, they store a number of bytes, each of which has an “address”– a unique number. There are a number of pins on the chip that are marked as address pins. You just need to set these pins high or low to indicate the binary value of the address you’re interested in. A few nanoseconds later, the chip will set another set of pins– the “data” pins– to high or low values to reflect the data that’s stored at that address. To read the contents of the ROM, all we have to do is write all the addresses in sequence to the address pins, and read the data from the data pins.
To hook up all those pins, we need to know what each physical pin on the chip does. The easiest way to get that information is to find the datasheet for the chip in question. Although these parts have been obsolete for years, datasheets describing most of them are still readily available online. Even if you can’t find a datasheet for your particular chip, you can often find one for a similar EPROM. Here are links to datasheets for the three chips shown above:
This is a map that shows what each pin on your chip does. The pins labelled with the letter “A” are the address pins, and the pins labelled “Q” are the data pins. The chip on the left has fifteen address pins A0-A14, which correspond to the bits of a 15-bit address. The pins Q0-Q7 correspond to the bits of the data byte.
There are other pins on your chip. If you’d like to know exactly what each one does, just about every detail you’d care to know is in the data sheet. If you just want to get up and running, though, here’s a quick cheat sheet:
- The “Vcc” pin is the power pin, and should be connected to +5V.
- The “GND” or “Vss” pin is the ground pin, and should be connected to ground.
- The “Vpp” pin is the programming voltage pin, and should be connected to +5V (unless it’s also one of the enable pins; see below).
- The remaining pins labelled “E”, “OE”, “G”, “CE”, etc. are pins that enable the inputs and outputs. All you really need to know about these is that they need to be enabled, and that they are active low. This means you tell the chip to enable these pins by hooking them up to ground, not +5V. You can tell that they’re active low because they either have a hash mark (#) beside their names, or a little horizontal bar is drawn over their names.
That’s it! We now have enough information to start wiring up our circuit.
Step five: Breadboarding.
It’s time to grab your trusty breadboard, some wires, and start plugging things in. The first step is to insert your chip into the breadboard. Make sure you align the semicircle on the end of the chip with the corresponding mark on your diagram. I started out by hooking up everything that wasn’t an address or data line. In this case, Vcc and Vpp are connected to power, and everything else that’s not an address or data pin gets connected to ground.
Next, hook up the address lines to your Arduino Mega. If you want to use the program provided below, you should hook up pins A0-A15 in order to the pins 26-41 on the microcontroller. (If you need to use different pins, it’s easy to change the code, but try to keep them in order!)
Now, do the same with the data pins: hook up Q0-Q7 in order to pins 2-10 on your microcontroller.
Once you have all the pins hooked up, connect the power and ground connections on your breadboard to the +5V and GND connections on your microcontroller. That’s it! No passives, just lots of wires.
Before you plug anything in to a USB port, though, take a minute to double-check that all your connections are right. With so many wires, it’s easy to knock one loose when you’re inserting another one.
Step six: Software.
Download this Arduino sketch from github, and open it in the Arduino environment. Before you upload it to your board, read the comments and change the MAX_ADDR value to match the size of your chip (and change the Q0 and A0 values if you’re using different pin numbers than I am). Then upload away! As soon as the program starts, it will start writing the data on the EPROM to your serial port at 115200 bps. To confirm that it’s working, open the serial terminal in Arduino and press the reset button on the board. You should see a river of fast-moving hexadecimal values rush by.
Now just use your favorite serial program to capture that data to a file. Congratulations! You’ve got disk full of meaningless hieroglyphics.
Step seven: Now what?
Now it’s time to go dowsing. The bulk of the ROM probably contains binary instructions, but anything could be in there– images, fonts, screed, mysteries.
For starters, a file full of space-separated hexadecimal values isn’t really much use to anyone. Here’s a simple python script that will convert those numbers into a binary file. Once you have a binary, you might want to try opening it in a hex editor. If you know the type of processor the board is using, you might try running it through a disassembler for that processor. Disassemblers for common processors like the Z80 are readily available.
Often there are a number of strings embedded in these ROMs; you can extract these with the unix “strings” utility, or just browse through the files and see what you come up with. One of my ROMs contained the string “
-Sixteen Bit Digital Audio System rev 1.32 copyright 1999 Gilderfluke & Co. DCM-“, which led me to this manual. Another has nothing but tantalizing, cryptic hints:
fUTIME ZONE SPLIT
fURDR NUMB 1/4 MIN.
Finding image or font data is a bit trickier, because while such data is often uncompressed, it can be represented in many ways. For instance, here’s a snippet of an image I generated from the ROM marked “Hebrew”, which is from an LED array control board and as expected contains both English and Hebrew glyphs:
To generate this image, I essentially just drew each byte as a “line” of eight pixels across. This would have created a very long, narrow image, so I cut up that “ribbon” of data into parts and put them side by side, creating the image above. Each character is stored as consecutive bytes in memory.
Now, let’s look at the character ROM from an Osbourne 1. What I did here is again draw out each bit as a dot, but instead of creating an 8-bit wide “ribbon”, I instead just drew each byte one after the other from left to right, wrapping when I reached 1024 pixels across:
The pixel data here is interleaved: first the first scan line of A, then B, then C, etc. through the entire font, and then the second scan line of A, B, C, etc.
Puzzling out how data like this is stored is mostly a matter of experimentation and expectation. How was the ROM used? Do you have schematics of the rest of the board, and what do they tell you? Did the device have a screen? A serial port?
Anyway, that’s the brink of the abyss. Take a gander and tell me what you see!
- I’m using a ChipKit Uno32 in the example below. An ordinary Arduino doesn’t have enough I/O pins! Sorry. ↩
- the bar for wits in this instance is pretty low. Unless you’re exceptionally addled you should be fine. ↩
- complete with instructions about who to kill next. ↩
- generally 1970-2000 or so. ↩
- How can something be “programmable” and still be considered “read only”? By giving up and calling it “non-volatile”. ↩
- the etching is controlled by photomasks; this is where the term “masked” comes from. ↩
- THIS IS COMPLETELY TRUE ↩
- you know, bedtime. ↩
- many early computer manufacturers created extensive technical manuals for their products; a surprising number of these are available online. Be aware that schematics are also often haunted. ↩