82_Computer_Grids

Grids-inspired trigger sequencer firmware for the Music Thing Workshop Computer.

Features:

• X/Y map control (switch Z in middle)
• Fill macro control (switch Z in middle)
• Per-lane density with Main / X / Y when switch Z is up (pattern map is held from the last middle position)
• Internal clock with optional external clock on PulseIn1 (swing applies to the internal clock only)
• Reset on PulseIn2
• Alt layer on long-press (Z) with knob pickup/catch behavior
• USB MIDI SysEx configuration transport with persistent flash config

Quick Start (User)

1. Flash UF2/82_Computer_Grids.uf2 (produced by a successful Build below, or supplied with the release).
2. With no pulse clock patched to PulseIn1, internal clock runs automatically.
3. With Z in the middle (normal): turn X / Y for map, Main for fill macro. With Z up: Main = lane 1 density, X = lane 2, Y = lane 3 (map stays where you left it in middle).
4. Patch outputs:
   • PulseOut1 and PulseOut2 for trigger lanes 1 and 2
   • CVOut1 for trigger lane 3 (digital pulse-style output)
   • CVOut2 for aux output (accent/clock/lane3 mirror, configurable)

Controls

Switch Z — middle (normal)

• Knob X: pattern map X position
• Knob Y: pattern map Y position
• Knob Main: global fill macro (all lanes, with per-lane scale/offset from config)
• Middle ↔ up: when you flip between middle and up, the current sound is kept until you move that knob more than a small deadband (so the same physical position does not jump to a new meaning).

Switch Z — up (per-lane density)

• Knob Main: density for trigger lane 1 (PulseOut1)
• Knob X: density for lane 2 (PulseOut2)
• Knob Y: density for lane 3 (CVOut1 pulse)
• Pattern map (X/Y on the Grids) uses the held knob map from the last middle position (CVIn1 applies once you have “taken over” X or Y after switching — see Inputs below)

Switch Z — down (momentary)

• Short press (press then release): tap tempo (internal clock only)
• Long press: toggle alt layer (knob pickup/catch). With middle + alt: Main / X / Y adjust chaos, BPM, and swing. With up, knobs stay on per-lane density; randomness (chaos) is still whatever you last set in middle+alt.

Alt Layer

When alt layer is active:

• Main adjusts chaos/randomness (used by the pattern engine)
• X adjusts internal BPM (bpm10 in config; used for the internal clock)
• Y adjusts swing (50% straight … 75% shuffle)

Changes are persisted with deferred flash save.

Inputs and Outputs

Inputs

• PulseIn1: external clock input
  • If connected, firmware follows external clock edges (straight timing; swing is ignored).
  • If not connected, internal clock runs (BPM + swing from config / alt layer / web editor).
• PulseIn2: reset input
  • Rising edge resets pattern phase.
• CVIn1: map modulation input
  • Assignable target: X, Y, or blended XY (via config).
  • While map knobs are frozen after a middle↔up change, CV1 is held off until you move X or Y past the takeover deadband (avoids double-applying the same offset).
• CVIn2: fill modulation input
  • Middle: adds to the global fill macro after Main has taken over following a middle↔up flip (initially on at power-up).
  • Up: adds to all three lane densities after any of Main / X / Y has taken over following a flip.

Outputs

• PulseOut1: trigger lane 1
• PulseOut2: trigger lane 2
• CVOut1: trigger lane 3 (digital pulse behavior)
• CVOut2: aux output mode (accent / clock / lane3 mirror)

LED Behavior

• LED 0: beat tick blink
• LED 1: fill macro brightness (middle) or lane 1 density (up)
• LED 2: lane 1 trigger activity
• LED 3: map X brightness (middle) or lane 2 density (up)
• LED 4: lane 2 trigger activity
• LED 5: lane 3/aux activity or alt-layer indicator (middle); lane 3 density brightness (up)

Web GUI

A basic web editor is included in:

• web/index.html

Open it in a Web MIDI-enabled browser, click Connect Web MIDI, select the card MIDI input/output, then use:

• Read From Device — sends SysEx request 0x01; the card replies with command 0x02 and a 7-bit-packed config payload (see sysex_spec.json).
• Apply To Device — sends current UI values via SysEx 0x03 to update running behavior (applied on the audio core on the next block).
• Save To Card — SysEx 0x04 marks config for flash write after about 1.5 s of no further changes (same deferred save as knob/SysEx edits).
• Load Defaults — fills the editor with built-in defaults (does not talk to the card until you Apply/Save).
• Start Monitor — periodically sends read requests and refreshes the UI.

The web UI includes paired sliders + numeric fields for main continuous parameters. The Backup section can export/import JSON snapshots of the editor state.

Connection notes:

• Use a USB-C data cable.
• Close Serial Monitor / other apps that may already own the device/MIDI port.
• Use a Chromium-family browser with Web MIDI SysEx enabled (iOS/Safari browsers are generally unsupported).

Attribution and licensing

This firmware includes adaptations derived from Mutable Instruments Grids:

• Pattern-map structure and interpolation approach inspired by Grids pattern generator
• Adapted node resource data used by the Grids map

Original project:

• Mutable Instruments / pichenettes eurorack Grids source:
  • https://github.com/pichenettes/eurorack/tree/master/grids
• Module documentation:
  • https://pichenettes.github.io/mutable-instruments-documentation/modules/grids/

The upstream Mutable Grids source is released under GPLv3 (or later). This folder is licensed accordingly; see COPYING for the folder-scoped licensing notice and caveat.

Credit

• Original Grids design and firmware: Emilie Gillet / Mutable Instruments
• Workshop Computer adaptation in this folder: community adaptation for Music Thing Workshop Computer by @philmillman
• Lots of inspiration and code borrowed from other cards in this repo, especially 20_reverb (USB bring-up and dual-core layout).

Releases

• Release 0.1.0 — April 30, 2026
  • Initial release
  • Includes:
    • Grids-inspired trigger sequencer
    • Web MIDI SysEx configuration
    • Basic browser GUI for reading/writing config
    • Persistent flash config

Build

I highly recommend using the computercard-dev-env.

From this folder:

make

That runs the Pico SDK CMake build and copies UF2s into UF2/. Without that helper, configure and build with CMake the same way as other Workshop_Computer/releases/* CMake cards.

UF2 output is copied to:

• UF2/82_Computer_Grids.uf2

Flash

Use your normal Workshop Computer flashing workflow (debug probe/OpenOCD or UF2 drag-and-drop workflow as used in this repo).

Serve the web editor

Serve web/ over http://localhost (or HTTPS), not file://, so the browser exposes Web MIDI — for example from this folder: python3 -m http.server 8080 --directory web.

Files of interest

• main.cpp - dual-core startup (ComputerCard audio on core 1, housekeeping + USB on core 0)
• GridsCard.cpp / GridsCard.h - card behavior, UI, clocking, I/O, SysEx handling
• GridsEngine.cpp / GridsEngine.h - pattern evaluation logic
• GridsResources.cpp / GridsResources.h - Grids map node resources used for interpolation
• ConfigStore.cpp / ConfigStore.h - persistent flash config
• sysex_spec.json — web/editor integration spec for config payloads (request/response command bytes included)
• web/ — browser GUI for reading/writing config over Web MIDI SysEx
• context.md — maintainer notes (Web MIDI over localhost, USB dual-core pitfalls, product string Workshop Grids for MIDI port filtering)

The GUI implements the same 7-bit block packing scheme documented in sysex_spec.json.

USB MIDI bring-up matches 20_reverb: 200 MHz boot clock, tusb_config.h with device + host on rhport0, tinyusb_host linked, 100 ms delay, then tud_init(0) or tuh_init(0) from USB_HOST_STATUS / board revision (same logic as reverb’s usb_worker), then board_init(). tud_task() / tuh_task() run on core 0; 48 kHz audio runs on core 1 (like reverb’s audio_worker).