$30 Clamp Meter Runs Full Doom Episode On Record Low Memory

A thirty-dollar FNIRSI DMC-100 clamp meter now hosts a complete, playable episode of DOOM, complete with all nine maps, the title screen, intermissions, the finale, the menu, and four save slots. Polish developer Artur Bieniek made this possible by adapting the doomgeneric engine, drawn from id Software’s source release, to the meter’s Artery AT32F415 microcontroller. That chip runs at 150 MHz, yet it provides only 32 kilobytes of RAM, an amount smaller than the 64,000 bytes needed for a single original Doom frame. Bieniek’s port therefore ranks among the leanest versions of the game ever made, beating the previous low of 64 kilobytes recorded on a Neo Geo release.

Bieniek opens up episode 1 of Freedoom Phase 1 using his modified code, but the core game logic remains the same as the original DOOM engine. He’s been reviewing demos back and forth tic by tic, and he’s pleased to report a perfect match. The color graphics look exactly like you’d expect on the meter’s 320 by 240 screen, but to keep it operating smoothly within the memory restriction, the port simply draws the view in one vertical strip at a time and feeds it to the display. The levels, textures, and less utilized code all sit on the meter’s 4 MB flash chip and are loaded only when needed, while the main program is a modest 99 kilobytes and is stored directly on the micro’s internal flash chip.

Performance is close to 29 frames per second, however it increases slightly in compact rooms and decreases in large open spaces. All of the sound effects originate from the meter’s built-in buzzer, so you just hear the weapon and enemy noises with no background music. Bieniek was able to get the controls to work with a DJI RC-N1 drone controller, which treats the meter as an Android phone and provides proper sticks and buttons to play with instead of the meter’s limited keys. The resulting result is more than playable, and Bieniek has demonstrated that it is feasible to clear numerous levels, and you can still return to the original firmware.

However, flashing the custom software would void the warranty, so be aware of this before proceeding. While the game is loading, the meter will be utterly unresponsive, and you will be unable to measure anything, as it must also be disconnected from any circuit or live conductor. The entire process, from entering upgrade mode over USB to copying the game data, is documented on GitHub, and the original firmware can be put back with the meter’s pictures restored. Everyday hardware continues to absorb the 1993 shooter in unexpected places, and this clamp meter now stands as one of the smallest successful hosts yet.
[Source]