Wenting Zhang appeared on the M5PaperS3 and determined its e-ink display screen may do greater than show static pages. The compact growth board from M5Stack carries an ESP32-S3 processor, a 4.7-inch 960-by-540 e-ink touchscreen, a easy buzzer, and a microSD slot. He turned the entire package deal right into a handheld that runs authentic Recreation Boy software program at a gradual 60 frames per second.
Most e-ink shows are famous for being slightly sluggish. It has rather a lot to do with how charged particles within the panel take their time drifting into place, thus a full refresh can take a whole bunch of milliseconds and ceaselessly produces a faint afterimage. Zhang stomped on these bodily constraints. He didn’t merely settle for the established order and dismiss these restrictions as the utmost. As an alternative, he created a bespoke driver that solely works with the show’s low-level parallel interface. This driver holds a super-compact state report for every pixel, with solely 4 bits per dot.
That state buffer receives a brand new set of picture information each sixtieth of a second, whereas the motive force nudges every pixel into place utilizing a collection of voltage modifications. It’s a intelligent strategy that renders the usual international lock, which requires the whole panel to finish one full cycle earlier than receiving recent instructions, fully out of date. The Recreation Boy panels are small (160 by 144 pixels), subsequently a crisp threefold upscale with slight dithering is properly inside the processor’s capabilities. Fortuitously, the entire energetic buffers match contained in the ESP32-S3’s extraordinarily quick inner SRAM.
The 2 cores on the board perform collectively, with one working the emulator itself. The second core is accountable for processing show updates and sending new information by way of DMA transfers timed to the vertical sync sign. This preserves the 60 Hz rhythm completely on beat even when the emulation workload modifications. Zhang tried a number of Recreation Boy emulator cores earlier than selecting CrankBoy, an optimized fork of Peanut GB. It offered the most effective trade-off between velocity and compatibility on this {hardware}. Most video games run near full velocity. The system will skip the odd body to maintain the timing simply excellent for sound and enter within the occasion of a demanding scenario. Sadly, Recreation Boy Coloration titles stay out of attain in the intervening time resulting from their roughly doubled processing demand.
The sound emanates from a single buzzer on the board. Zhang created a rapid-switching scheme that cycles between crude approximations of the 4 authentic Recreation Boy audio channels. The tip output is acknowledged chiptune music moderately than actual waveform playback, however it preserves the essence of the video games with out the necessity for added gear. The touchscreen contains the entire controls. The panel’s decrease portion shows a Recreation Boy-style directional pad and varied motion buttons. Any faucets register instantly. There may be experimental Bluetooth LE gamepad help, though it solely works with a restricted variety of controllers proper now.
Saved information is saved on the microSD card, and the {hardware} energy button solely cuts energy, with no shutdown course of (Zhang added a guide save button to the display screen). Fast save states add an additional diploma of safety throughout prolonged gaming classes. All the challenge’s supply code (generally known as Paper Boy S3 in some locations) is now out there on GitLab. There’s additionally a separate proof-of-concept JIT recompiler that one other developer labored on, demonstrating one strategy to go even sooner if somebody needs to take it a step additional.
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