Updating a Vintage Atari Pen Plotter with an ESP32 Controller
Bart Dring got his hands on an Atari 1020 pen plotter, and is updating it with a custom ESP32 controller board.
Modern video game consoles are complete multimedia machines capable of doing much more than running games, but that is all that most vintage consoles were capable of. Except that’s not quite true. In the early ‘80s, many manufacturers were building affordable home computers that blurred the line between PC and console. Atari was one of the most popular manufacturers doing that, and their line of 8-bit home computers were designed specifically with gaming in mind. However, they were still fully-functional computers, and there was even a pen plotter available to use with them. Bart Dring got his hands on one, and is updating it with a custom ESP32 controller board.
The Atari 1020 pen plotter was designed by ALPS Electric, and contained an ALPS DPG1302 drawing mechanism that was also used in similar vintage plotters from Commodore, Tandy, Texas Instruments, and even Mattel. It was capable of plotting up to 80 columns of text, and could even draw graphics using four colored pens. In a time before color inkjet printers, pen plotters like this were extremely useful. But even if you can find a functioning plotter today, you still need the corresponding computer to use it. That’s why Dring is replacing the control board with a custom-designed board featuring an ESP32 microcontroller.
While the hardware Dring needs to control is simple—just a couple of unipolar stepper motors and a solenoid—the way they are controlled is a little unusual. The biggest challenge comes from the homing mechanism, which repeats a back-and-forth sequence in order to find pen #1 using a reed switch. Dring’s controller is based on a custom implementation of Grbl, which only has built-in support for a standard limit switch-based homing operation. To overcome that, Dring will have to write a custom homing sequence set of operations. Even so, he has already ordered the custom PCB needed to replace the controller. That shares the same footprint as the original control board, so it should be a drop-in replacement that doesn’t require any modification. Be sure to follow along with the project to see his progress with the rest of the project.