October 29, 2025
HAL on a dime, comments on fire
I made a 10¢ MCU Talk
Tiny 10¢ chip speaks ‘HAL’ and the comments explode
TLDR: A 10¢ microchip played a 6‑second HAL quote by ultra‑compressing audio to fit tiny memory. Commenters cheered the clever hack while bickering over a simple speaker filter, extra memory add‑ons, retro on‑device speech (SAM), and phone‑era formats—proof that tiny tech can spark big opinions.
A 10¢, 8‑pin microchip just said “Open the pod bay doors, HAL,” and the internet lost it. The maker squeezed about 7 seconds of audio into teeny storage using a super‑simple, 2‑bit scheme that stores only tiny changes between sounds, then blasted it through a tiny speaker at 8,000 samples per second. Cue the crowd: one comedian quipped they expected a “very poorly paid Marvel talk,” while nostalgia fans cheered the throwback vibes to Speak & Spell, BBC Micro’s “say” command, and classic Mac voices. One history buff even dropped a nod to GSM phone tech, suggesting the AMR voice format for extra points.
Then the engineering drama hit. Audio tinkerers called a “missed opportunity” for a basic low‑pass filter—aka a tiny part that would smooth the buzzy edges and make it sound nicer. Hardware hoarders demanded more storage with a cheap add‑on memory chip. And the purists? They want no recorded clip at all—go full retro speech synth with SAM so the chip literally talks on its own. The vibe: half science fair flex, half ’80s time capsule, all comment‑section chaos. Love it or nitpick it, everyone agrees on one thing: hearing HAL on a dime feels absurdly cool—and that’s exactly why the thread blew up.
Key Points
- •An 8-pin CH32V003 RISC-V MCU plays spoken audio using PWM as a rudimentary DAC at 8 kHz.
- •A ~6-second audio clip must fit in 16 KB of flash alongside playback code, requiring strong compression.
- •Evaluated codecs show 16-bit/8 kHz PCM (~96 KB) and 8-bit PCM (~48 KB) are too large; 4-bit IMA ADPCM (~24 KB) and QOA (~19 KB) still exceed limits.
- •2-bit ADPCM compresses the clip to under 12 KB, leaving room for code; the decoder compiles to ~1,340 bytes.
- •2-bit ADPCM uses adaptive prediction and step sizes, mapping 2-bit codes to step adjustments for compact speech playback.