Keypad synth revB

BLASTEROID MEGASYNTH

Experimental industrial ambient on an ESP32-S3. A slow machine drone you build from layers, two robot mouths (SAM, the 1982 Software Automatic Mouth, and the Talkie Speak & Spell LPC voice) that can freeze into drones, get scratched on a knob and talk to each other, a box of industrial noises, and a huge reverb "space". It runs on a 4x4 keypad, one rotary pot, a 128x128 OLED and a small speaker.

At boot it plays a generative splash that's different every time: two random geometry scenes (string-art mandala, polygon rings, flow-field particles, a rotating tunnel, a 3D Lissajous knot), glitch cuts. Then everything converges into the Blasteroid: a cyborg cyclops in wraparound shades. His eye charges up, two lasers burn BLASTEROID / MEGASYNTH in from opposite ends, SAM says the name, and Talkie answers "OPERATIONAL".

The board is a single-sided PCB designed to be milled on a desktop CNC. The modules plug into headers or edge pads, so there's no SMD soldering.

What's in here

Parts

Pinout

The amp uses the TX/RX pins, so USB CDC On Boot must be Enabled (serial goes over native USB).

Build the firmware

1. Arduino IDE (or arduino-cli) with the ESP32 core 3.x and the U8g2 library.
2. Board settings: ESP32S3 Dev Module, USB CDC On Boot: Enabled, PSRAM: enabled. arduino-cli FQBN: esp32:esp32:esp32s3:CDCOnBoot=cdc,PSRAM=enabled
3. Flash keypad_bringup first to check the keys, pot, OLED and speaker, then blasteroid_megasynth.

arduino-cli compile --fqbn esp32:esp32:esp32s3:CDCOnBoot=cdc,PSRAM=enabled firmware/blasteroid_megasynth
arduino-cli upload  --fqbn esp32:esp32:esp32s3:CDCOnBoot=cdc,PSRAM=enabled -p COMx firmware/blasteroid_megasynth

Tips:

• The OLED needs the U8G2_SH1107_PIMORONI_128X128 constructor. The generic SH1107 one shifts the picture by 32 px.
• If the SuperMini sits silent after an upload, press RST. The auto-reset can leave it in the bootloader.
• If the knob works backwards, turn the pot module round. Swapping its outer legs reverses the direction.

Playing it

[MODE ] [ pad 0 ] [ pad 1 ] [ pad 2 ]      left column: tap = quick action,
[FX   ] [ pad 3 ] [ pad 4 ] [ pad 5 ]      HOLD = the screen shows what the 12 pads do
[SEQ  ] [ pad 6 ] [ pad 7 ] [ pad 8 ]
[SHIFT] [ pad 9 ] [ pad 10] [ pad 11]

The knob

• Knob alone: the current voice FX's main control: pitch, echo feedback, radio tuning, grain density, depth, vocoder wet, choir breath.
• SHIFT + knob = SCRATCH: scrub through the current SAM or Talkie word like a record under your hand. It's silent while the knob is still.
• FX + knob = SPACE: from dry and close to a huge, long reverb.

Modes

• HUM: drone layers on/off: MAINS (transformer hum), SUB, PAD, CHOIR (morphing vowel), METAL (inharmonic FM girder), WIND, RADIO (shortwave whistle and crackle), PULSE (heartbeat). Also DRIFT (the chord wanders i-bVI-bIII-bVII), KEY -/+, and CHORD (fifth, minor7, sus2, minor9, void).
• SAM: 12 words (OHM, SILENCE, SIGNAL, MACHINE, BREATHE, ECHO, VOID, DRIFT, STATIC, RESONANCE, FREQUENCY, WE ARE LISTENING). Tap = say it, hold = freeze it into a granular drone.
• TALK: four Talkie banks: SIGNAL, NUMBERS (numbers station), ELEMENTS, MACHINE. Tap = say it, hold = freeze the mouth on one frame, humming in the drone's key.
• MACH: 12 industrial sounds: KLANK, PIPE, HAMMER, HISS, GEIGER, RELAY, SERVO, SONAR, CHAIN, DRIP, HORN, THUD. Hold = repeat.
• CROSSTALK: SAM and Talkie take turns, a word per bar, over whatever is playing.
• With REC on, voices and machines are quantized into the 16-step sequencer.

Make the board

Single-sided, all copper on B.Cu, made for isolation milling. The Gerbers also work at a board house as a 1-layer board. Full steps are in hardware/cnc/CNC_CHEATSHEET.txt: V-bit isolation, 1.0 mm drill, 2.0 mm drill, outline score. The keypad's pins solder flat onto edge pads, and the pot stands in 3 holes.

Isolation gutters: with a single 0.1 mm V-bit pass, several SuperMini pads stayed shorted to the ground pour. load_and_mirror.tcl now isolates with 3 passes (about a 0.3 mm gutter). The ready-made 1_isolation_0.1vbit.nc is the older single-pass file, so regenerate it with FlatCAM (set the path at the top of the script). After milling, meter every header pad to GND before soldering, or flash short_finder on a populated board.

Print PRINT_1to1_fit_test.pdf at 100% and check your modules against it before milling. The keypad and pot outlines were measured from photos.

Credits and license

• SAM (Software Automatic Mouth) by Mark Barton / Don't Ask Software (1982). C port by Sebastian Macke, ESP8266SAM by Earle F. Philhower III.
• Talkie LPC speech by Peter Knight, extended by Armin Joachimsmeyer (vocabulary data bundled).
• U8g2 by olikraus; esp-dsp and the ESP32 Arduino core by Espressif.
• Co-created by Mark Hellar and Claude (Anthropic). PCB milled and soldered by Mark Hellar.

Licensed under the GNU GPL v3 (see LICENSE), matching the bundled SAM and Talkie code.