belt-alchemy

Belt — live vocal processor: pitch correction, four diatonic harmony voices, a doubler and a formant control — for the Hermetic Modular Alchemy Lab V2, built on the Alchemy SDK.

Same C engine as schwung-belt for the Ableton Move, recompiled for six pots on two pages, three buttons, six CV jacks and 102 LEDs. Sing into J1/J2; the module corrects you to the KEY and SCALE at the RETUNE speed and stacks up to four harmonies that walk the scale from what you sing. The KEY ring is a tuner.

Status: v0.1.0 builds and passes its native tests. Nothing has been heard yet. See DESIGN.md for the control map, what is verified and what is not. The open question is CPU: seven pitch-shifting voices on one Cortex-M7 has not been measured.

Build

Requires arm-none-eabi-gcc, make, dfu-util.

git clone --recurse-submodules <this repo>
cd belt-alchemy
make libdaisy        # once
make                 # build/belt_alchemy.bin
make test            # native tests, no hardware

Flash

Front USB-C with the factory bootloader: hold B3 during the ~2 s boot window (rings spin a warm-white comet), the rings switch to a slow breathe, then:

make program-dfu

or the web programmer. Once this firmware is running on the front port, make program-live reboots and flashes without touching the module.

Bench setup (Hermetic's intdfu bootloader on the Seed's micro-USB): same gesture on the micro-USB port; build with BENCH_USB=1 if you want HostLink there too.

Firmware on the SD card

Put .bin files built for the Alchemy Lab bootloader in a folder named alchemy on a FAT32 card. Hold B2+B3 for two seconds, tap B1 to the Firmware page, pick a file with the top-left pot, then turn the top-right pot down and all the way up. It writes, verifies, and reboots into the chosen firmware. Every firmware in this family (Smack, Mark, Belt) carries the same page, so the card is the module's library and any of them can hand the module to any other.

The site

docs/index.html is the operation manual, a single file meant for GitHub Pages from main:/docs. Its panel drawing is generated from the SDK's KiCad front-panel template by tools/emit_panel_geometry.py; run it with --check before publishing and --write after the template changes, and never hand-edit the coordinates. The repository URL the page links to is one constant at the top of the file.

Files on the card over USB

tools/hostlink-fs.mjs speaks HostLink's filesystem block, so images reach the card without pulling it:

node tools/hostlink-fs.mjs info
node tools/hostlink-fs.mjs ls /alchemy
node tools/hostlink-fs.mjs put build/belt_alchemy.bin /alchemy/belt_alchemy.bin --overwrite

The picker lists files in on-disk order, one dot each, so the order you upload them is the order the FILE pot walks.

Family

smack-alchemy, mark-alchemy and this repository share, by copy, the picker, the SDRAM allocator, the linker script, the card tool and the shape of the Makefile and main file. A fix in one belongs in all three.

Not a Hermetic Modular product

Custom firmware. Hermetic Modular did not write, test or endorse it; ask here, not there.

License

MIT (this firmware). The vendored engine is Tim Cox's; see the file headers.

src/usbd_ctlreq_uac.c is STMicroelectronics' usbd_ctlreq.c from the STM32 USB Device Library (as shipped in libDaisy), changed only to allow three interfaces; it stays under ST's license, in src/LICENSE-ST-USB.md.