218e v3 Rewired
A patched build of the stock v36.9 firmware for the Buchla 218e V3 touch
keyboard.
Features
-
Reworked pressure response.
-
Pressure-based portamento.
-
Reworked arpeggiator with latching.
-
Arpeggiator controls (random octave walk, random tempo, random note order)
-
Global pressure-responsive vibrato
-
Step sequencer, 64 steps with rests, ties and 303-style slides,
recorded and played from the preset pads.
-
External clock divide — the arpeggiator rate knob divides a patched-in
clock, /1 to /8.
-
Alternate tunings switched from edit mode, including Scala keyboard
maps and scales that repeat at something other than the octave.
-
Per-note pitch calibration.
-
Selectable volts per octave
-
Quantized preset voltages, snapping the add-to-pitch transposition to
the selected tuning.
-
The portamento banana jack as a transposer, shifting the keyboard and
its MIDI notes by whole degrees of the selected tuning.
-
Settings over MIDI. Every option above, the arpeggiator's pattern
bank, the tunings, the pitch calibration and the volts per octave can be
changed from the builder page without flashing again: the page sends
them over Web MIDI, and the keyboard restarts to run a changed option.
See docs/SETTINGS.md.
Build it in your browser
The page can also tune your 208 for you: it plays C0 to E6 into the keyboard
over MIDI, listens on an audio input, and tunes each note of the table on the
instrument until it plays in tune. Send or flash the result; another run starts
from that table and corrects what is left.
Then run the flasher for your platform from this repository:
| Platform | Flasher |
|---|
| macOS | mac/Program218e_v3_Rewired_macOS.command |
| Windows | windows/218e_Rewired_Flasher.bat |
It opens with a choice: flash firmware, or get a keyboard out of DFU mode
after an interrupted flash. The second writes nothing.
Controls
Playing
| Control | What it does |
|---|
| Knob 1 | Arp note order: press order → random. |
| Knob 2 | Arp rhythm: even pulses → randomly spaced. |
| Knob 3 | Random octave displacement per arp note. |
| Knob 4 | Global vibrato, depth and rate together, up to 33 cents at ~6 Hz. Pressure scales it from half to full. |
| Portamento | How much pressure a second held note needs to pull pitch toward it. Off at zero; no time-based glide at any setting. |
| Portamento in banana jack | With portamento_in = "transpose": transposes the keyboard, the sequencer and the MIDI notes by whole degrees of the current tuning, one period of it per 4 V — so the jack’s 0–10 V is about two and a half periods. The pitch ramp’s own scaling does not change it. Otherwise adds to the portamento time, as the factory has it. |
| Arp switch | latch / regular / off. In latch, keys are toggles. |
| Octave pads | Tap pad 4 twice, quickly: the octave pads play one octave higher. Tap pad 1 twice to go back. The pad flashes to confirm; the choice is remembered. |
Edit mode
| Control | What it does |
|---|
| Knob 1 | Scales the whole pressure window, 1.21x–0.70x clockwise, unity at 4.1 of 10. |
| Key 28 / Key 27 | Tuning slot select. LEDs: rem-en = slot 0, trn = slot 1, both dark = slot 2. |
Building from source
Only for changing the firmware itself — adding options, editing the assembler
source, or reproducing an image independently. To use the firmware, build it
on the page instead;
both toolchains produce identical images from the same options.
cp /path/to/218eV3_v369_DFU.hex firmware/ # your own copy, once
python3 tools/build.py --no-ghidra # writes build/
python3 tools/test.py --golden # rebuild and compare
Python 3.11+; Ghidra 12.x only if you drop --no-ghidra. The options
live in config/218e.toml, and tools/avr32/ holds a
second, Ghidra-free toolchain that assembles the same firmware in JavaScript —
tools/avr32/sweep.py builds every option both ways and checks the images
match. See docs/BUILD.md.
Layout
config/ the options — the only file you normally edit
tunings/ Scala files, with .kbm keyboard maps where the degree
count is not 12 or the period is not the octave
calibration/ measured per-key tracking error — instrument-specific
src/ Ghidra scripts: the AVR32 assembler and verification tools
tools/ build.py, and avr32/ — the Ghidra-free build
web/ the builder page
mac/ windows/ the flashing kits
docs/ what changed, and how to build
Licensed under the Unlicense; the bundled flashing tools keep
their own — see THIRD-PARTY.md.
