Pi-Pico-Random-Looping-Sequencer-Firmware

C++ firmware for the Pi Pico Random Looping Sequencer Eurorack module. Host-agnostic engine + a macOS playground for development; a Pico-SDK host is planned (see "What's intentionally not here" below).

This is a rewrite of the MicroPython firmware that lives in the parent repo under Software/. The MicroPython version is still the running firmware on hardware today; this C++ tree is the path forward.

Quick build (macOS playground)

A native macOS playground that runs the same rls::SequencerEngine class that will (later) be linked into a Pico-SDK firmware host. No hardware required.

Built mirroring the pattern documented in the vault note Quick Tips/Simulating module UI on macOS and the reference implementation in DIYSynthMNL/vcdo-daisy. Differences from that reference:

• No PortAudio. The sequencer is logic-only; the note's adaptation table says to replace audio with a std::chrono tick thread. That's what ClockThreadMain does — sleeps to the next half-period at the configured BPM and pulses the engine's OnClockEdge.
• 6×8 bitmap font in FakeOled.h. vcdo-daisy didn't need text on its fake OLED (just a scope); a sequencer needs "STEP 05/16 BPM 60" so the font is inlined here.

Build

One-time:

brew install glfw pkg-config

Then:

cd Firmware
make            # first run clones Dear ImGui v1.91.0 into ./imgui/
./playground
# or
make run

What you see

Window	Contents
Sequencer Controls	Transport, BPM, scale combo, starting note, octaves, probabilities, modes
Simulated OLED (128×64)	Header bar, status line, 16-step grid (two rows of 8 cells). Current step is filled; trigger-on cells are outlined; out-of-range cells are a single centre pixel. Status text below shows step / DAC / TRIG state

Keymap

Key	Action
S	Toggle internal clock
G	Manual clock pulse (works whether internal clock is running or not)
R	Reset engine (clears CV/trig sequences to defaults, current step to 0)
Esc / Q	Quit

All other params are driven via ImGui widgets in the Controls window.

Files

File	Purpose
SequencerEngine.h/.cpp	Host-agnostic engine. No <machine>, no GPIO, no pico/stdlib.h. Port of Software/main.py
Scales.h	C++ port of Software/lib/mcp4725_musical_scales.py — 46 scale intervals + BuildScale() helper
FakeOled.h	128×64 monochrome buffer with line/rect/text primitives. 6×8 inline bitmap font
playground.cpp	macOS host: GLFW + Dear ImGui window, clock thread, key handling, OLED render
Makefile	macOS-only build recipe (clones ImGui on first run)

What's intentionally not here

• Pico-SDK firmware host (main.cpp). That's the next chunk of work. When written, it lives next to this code and links the same SequencerEngine.{h,cpp} and Scales.h. The engine API takes a now_ms argument exactly so the same code runs under both hosts.
• The hardware menu UX. The playground uses ImGui sliders directly to drive params — it's for engine development, not menu UX testing. The on-OLED menu remains the Pico host's responsibility.

Tested on

macOS 25.3 (Darwin), Apple clang 17, glfw 3.4, Dear ImGui v1.91.0.