Reviving the Apple 410 Shade Plotter

After seeing a few of the jaw-losing and shocking plotter artwork that’s been popping up on #plottertwitter this three hundred and sixty five days, I obvious to earn in on the stress-free. We don’t have an Axidraw or other in vogue plotting instrument to hand, however I did have a hazy memory of somebody donating a sweet giant-format HP plotter of some kind to NYCR a few years back. Armed with a ladder and flashlight, I scoured the loft for a chunk and at closing emerged filthy however form of victorious, with this:

Spoiler alert: here is now not any longer going to be a sweet giant-format HP plotter

oh hai

Train hey to the Apple 410 Shade Plotter. It’s location up adore many low-designate plotters of the period, with a plotter head traveling on the Y axis (left-to-factual going thru the printer) and a roller below the paper interesting it along the X axis (up-and-down) as it goes. A solenoid pulls the pen head down, and a limit swap on the left stop of the Y axis hurry enables the printer to dwelling itself. That’s it!

What makes is a coloration plotter, clearly, is the multi-pen head.

I adore this originate moderately a chunk.

There’s a pawl on the left stop of the head’s hurry. Because the head moves to the factual, it catches on to a peg on the head’s carousel, rotating it an eighth of a flip. On this vogue the plotter can (a chunk slowly) swap between pens of diverse colors. It’s a edifying, low-designate originate, and as long as you protect your quantity of pen swaps down, it doesn’t occupy your plots appreciably slower.

Whereas you didn’t know Apple made a plotter, successfully, they didn’t. It’s if truth be told a in an analogous contrivance vague Yokogawa YEW PL-a thousand. There have been no reference manuals obtainable online that I may well possibly get, however presumably Apple itself can lend a hand?

This didn’t work.

As charming the theory of rolling wild-eyed staunch into a Genius Bar with a thirty-plus-three hundred and sixty five days-outdated plotter and screaming “I NEED THIS WORKING BY MONDAY” used to be, I figured if I if truth be told wanted this part running I’d must earn it chugging myself. Despite the indisputable truth that I couldn’t get a snort reference wherever, I was ready to get a few snippets here and there (adore the configuration file incongruously pasted into the wikipedia web page) and, vitally, an outdated carrier manual which had the dip swap settings for moderately diverse serial port configurations.

I dispute “vitally” here this capability that of ordinarily after I must opt out the baud rate on a mysterious serial instrument, I’ll factual attempt connecting to it at moderately diverse flow/parity settings, toss a few linefeeds at it, and watch if the response looks to be like legible or on the least consistent. That formula wasn’t yielding any results for me this time. Because it turns out, the 410 didn’t answer to commands with acknowledgement or error codes. As a ways because the serial connection went, it used to be totally nonetheless. There is one bit of feedback, though. When you send a message the plotter doesn’t adore, it lights up a jaunty red ERROR led, which stays lit until it receives a reset snort or you restart the plotter. Tough.

Fortunately, the plotter does have a self-take a look at mode which plots text, graphs, circles, and other complex designs. In actuality, if you explore for the Apple 410 on YouTube you’ll get a few movies of the self-take a look at running. I figured that the script for that self-take a look at needed to be most modern somewhere in the firmware, and moreover you realize what that formula.

It’s ROM-dumping time!

This instrument is as straightforward internally as it is externally. What you’re here is a Z80 processor, an additional IC to tackle the serial interface, rather RAM, a few ROMs, a vitality present and a few driving common sense for the motors and panel switches. The ROMs were socketed and clearly labeled; yanking, dumping, and reinstalling them used to be a poke. Shopping thru the firmware quick bought me to precisely what I was buying for: the text of the self-take a look at script.

Ah, that’s the stuff.

Having a sight for other instances of the snort codes quick bought me to a dispatch desk, which meant I may well possibly enumerate all of the nice commands for the plotter. From this I was ready to cobble together a tough snort reference. A pair of straightforward take a look at plots later, we were in change!

There used to be one closing thorny patch to solve, though. As you’ll lift, the plotter doesn’t send any responses over the serial connection. As you’d count on of a instrument of this traditional, there’s no longer diverse RAM to support as a buffer, so that that that you will be ready to’t factual send a entire complex station straight away. The plotter must point out that that you will be ready to attain when the buffer is beefy, and for this it uses hardware handshaking. DTR/DSR hardware handshaking is a (now infrequently-ancient) technique for out-of-band signaling over an RS232 connection. Genuinely, when the plotter objects the DSR bit, it’s pronouncing “I’m beefy, daddy,” and if truth be told powerful adore a toddler, if you protect feeding it it would vomit in each place. If your USB to serial adapter handles hardware handshaking successfully, extra vitality to you, however mine doesn’t, so I stopped up flushing the the connection and checking the DSR line manually after every byte. It’s grotesque, nonetheless it works.

And that’s it. Whereas that that you will be one in every of the presumably dozen folk worldwide saddled with one in every of those beasts, I’ve got a half of-assed python library that can earn you started. Maintain stress-free!

(And if you’re questioning how I’m getting those high quality rotund traces with dried-out plotter pens from the eighty’s, that’s one more blog post.)