Reviving the Apple 410 Color Plotter

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Dec 132017

Apple 410 plotter drawing hexagonal spanning tree

After seeing some of the jaw-dropping and inspiring plotter art that’s been popping up on #plottertwitter this year, I decided to get in on the fun. We don’t have an Axidraw or other modern plotting device handy, but I did have a hazy memory of someone donating a sweet large-format HP plotter of some sort to NYCR a few years back. Armed with a ladder and flashlight, I scoured the loft for a bit and eventually emerged filthy but sort of victorious, with this:

Apple 410 Color Plotter box

Spoiler alert: this is not going to be a sweet large-format HP plotter

apple 410 plotter

oh hai

Say hello to the Apple 410 Color Plotter. It’s set up like many low-cost plotters of the era, with a plotter head traveling on the Y axis (left-to-right facing the printer) and a roller underneath the paper moving it along the X axis (up-and-down) as it goes. A solenoid pulls the pen head down, and a limit switch at the left end of the Y axis travel allows the printer to home itself. That’s it!

What makes is a color plotter, of course, is the multi-pen head.

The four-pen plotting head.

I like this design quite a bit.

There’s a pawl at the left end of the head’s travel. As the head moves to the right, it catches on to a peg on the head’s carousel, rotating it an eighth of a turn. In this way the plotter can (a bit slowly) swap between pens of various colors. It’s a nice, low-cost design, and as long as you keep your number of pen swaps down, it doesn’t make your plots appreciably slower.

If you didn’t know Apple made a plotter, well, they didn’t. It’s actually a similarly obscure Yokogawa YEW PL-1000. There were no reference manuals available online that I could find, but maybe Apple itself can lend a hand?

apple support

This didn’t work.

As charming the idea of rolling wild-eyed into a Genius Bar with a thirty-plus-year-old plotter and screaming “I NEED THIS WORKING BY MONDAY” was, I figured if I really wanted this thing running I’d have to get it chugging myself. Although I couldn’t find a command reference anywhere, I was able to find a few snippets here and there (like the configuration file incongruously pasted into the wikipedia page) and, vitally, an old service manual which had the dip switch settings for various serial port configurations.

I say “vitally” here because ordinarily when I need to figure out the baud rate on a mysterious serial device, I’ll just try connecting to it at various speed/parity settings, toss a few linefeeds at it, and see if the response looks legible or at least consistent. That approach wasn’t yielding any results for me this time. As it turns out, the 410 didn’t respond to commands with acknowledgement or error codes. As far as the serial connection went, it was completely mute. There is one bit of feedback, though. When you send a message the plotter doesn’t like, it lights up a jaunty red ERROR led, which stays lit until it receives a reset command or you restart the plotter. Rough.

Luckily, the plotter does have a self-test mode which plots text, graphs, circles, and other complex designs. In fact, if you search for the Apple 410 on YouTube you’ll find a few videos of the self-test running. I figured that the script for that self-test had to be present somewhere in the firmware, and you know what that means.

YEW PL-1000 logic board

It’s ROM-dumping time!

This device is as simple internally as it is externally. What you’re looking at here is a Z80 processor, an additional IC to handle the serial interface, a bit of RAM, a few ROMs, a power supply and some driving logic for the motors and panel switches. The ROMs were socketed and clearly labeled; yanking, dumping, and reinstalling them was a breeze. Browsing through the firmware quickly bought me to exactly what I was looking for: the text of the self-test script.

hexdump of rom with test script

Ah, that’s the stuff.

Searching for other instances of the command codes quickly bought me to a dispatch table, which meant I could enumerate all the valid commands for the plotter. From this I was able to cobble together a rough command reference. A few simple test plots later, we were in business!

There was one last thorny patch to resolve, though. As you’ll recall, the plotter doesn’t send any responses over the serial connection. As you’d expect of a device of this vintage, there’s not a lot of RAM to serve as a buffer, so you can’t just send a whole complex plot at once. The plotter needs to let you know when the buffer is full, and for this it uses hardware handshaking. DTR/DSR hardware handshaking is a (now rarely-used) technique for out-of-band signaling over an RS232 connection. Essentially, when the plotter sets the DSR bit, it’s saying “I’m full, daddy,” and very much like a toddler, if you keep feeding it it will vomit all over the place. If your USB to serial adapter handles hardware handshaking well, more power to you, but mine doesn’t, so I ended up flushing the the connection and checking the DSR line manually after every byte. It’s ugly, but it works.

And that’s it. If you are one of the maybe dozen people worldwide saddled with one of these beasts, I’ve got a half-assed python library that will get you started. Have fun!

(And if you’re wondering how I’m getting those nice beefy lines with dried-out plotter pens from the 80’s, that’s another blog post.)


May 052014

A quick word of warning for those coming to Laser Night tonight: our laser is having some power issues and is not operating at 100%. We’re working to fix the issue as quickly as we can, but we probably can’t cut anything thicker than a couple of millimeters at present. We’ll sing out once everything’s up and running again!

 Posted by at 3:30 pm
Apr 212014

Interactive Show

Get that Club Mate cold and those soldering irons hot because it’s time for another Interactive Show! We’re putting out the call to hackers around the globe to come show your stuff at our annual party.

This year there’s no theme– it’s a free-for-all! Have something blinking and beautiful? Something that bleeps or bloops? Anything interactive goes!

This year’s show will be June 7th. If you’re interested in being part of a show, drop us a line at! Try to get in touch by May 7th so we can make sure there’s space for your project. Hope to hear from you soon!

Props to Olivia Barr for our awesome gif flyer this year!

 Posted by at 5:41 pm


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Feb 042014

Once there was a box. Inside the box was a board, and inside the board was a chip. Inside the chip was a carrier, and on that carrier was a die. And when the die came off the carrier it broke, and the pieces looked like this:


More pretty pictures below.

Continue reading »

 Posted by at 10:38 am
Nov 252013

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!

May 242013

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.
Minitel 1B US
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*, 80×72 pixel black and white CRT display. By cranking the serial port up to 4800 blazin’ bits per second and reducing the number of color swaps, you can view the genius of the internet at such blinding speeds that you’ll think that you’ve suddenly been transported to a Jetsonian future of videophones and cars that collapse into briefcases. It’s just that advanced. See for yourself:

(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!

 Posted by at 9:08 pm
May 112013

Reading punched tape

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.

Tape reader parts

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.)

 Posted by at 6:17 pm
May 092013

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.

 Posted by at 8:54 pm
Mar 312013

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 clamps.

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:

  • Clamps!
  • 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!)
  • Clamps!
  • Files!
  • 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!

Files, on floppy and off!

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!

(We’re not kidding about the mill.)
It's a mill.

 Posted by at 10:38 pm