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cmods

Tools for building MicroPython and CircuitPython with LVGL user C modules.

Layout

cmods/
  micropython/              MicroPython clone (local, gitignored)
  circuitpython/            CircuitPython clone (local, gitignored; pin 10.2.1)
  lv_micropython_cmod/      LVGL + bindings generator
  pydisplay_cmods/          Display helpers
  manifest.py               Frozen Python modules
  build_unix.sh             Build Unix port
  build_esp32.sh            Build ESP32 port
  build_cp_unix.sh          CircuitPython unix port (coverage variant)

First-time setup

  1. Clone MicroPython and CircuitPython next to this tree (both gitignored; not submodules):
git clone https://github.com/micropython/micropython.git micropython
git clone https://github.com/adafruit/circuitpython.git circuitpython
cd micropython && git submodule update --init --recursive && cd ..

Pin CircuitPython to the latest stable release (not main):

cd circuitpython
git fetch --tags
git checkout -B circuitpython-10.2.1 10.2.1
make fetch-all-submodules
cd ..

Use git describe --tags --exact-match inside circuitpython/ to confirm 10.2.1. Do not git pull on main — that returns to the development branch.

  1. Initialize submodules inside lv_micropython_cmod/ (lvgl, pycparser, etc.).
  2. Generate LVGL bindings (required before any build):
./lv_micropython_cmod/regenerate_lvmp.sh
  1. Build a port, e.g.:
./build_unix.sh

LVGL bindings

Bindings are not committed to the repo. Regenerate after changing:

  • lv_micropython_cmod/lvgl/ (LVGL submodule)
  • lv_micropython_cmod/lv_conf.h
  • lv_micropython_cmod/binding/ (modular generator; primary)
  • lv_micropython_cmod/gen_mpy.py (regression reference only)

Generate

./lv_micropython_cmod/regenerate_lvmp.sh

Output (gitignored):

lv_micropython_cmod/generated/
  lvmp.c          # MicroPython bindings (compiled into firmware)
  lvmp.c.pp       # preprocessed lvgl.h
  lvmp.c.json     # API metadata
  lvcp.c          # CircuitPython bindings (phase 7; merge via LVCP_MODULE_GLOBALS)
  lvcp.c.pp
  lvcp.c.json

Modular generator

gen_lv_bindings.py is the supported entry point. It uses the binding/ package:

lv_micropython_cmod/binding/
  cli.py              argparse, --target micropython|circuitpython
  preprocess.py       gcc -E preprocessing
  context.py          BindingContext, regex patterns
  parse.py            AST helpers (pycparser)
  helpers.py          name sanitization, LVGL pattern matching
  analyze.py          AST analysis and metadata extraction
  runtime.py          shared generation state (sync hub)
  emit_c.py           MicroPython C source emission
  emit_circuitpython.py CircuitPython emission (phases 1–7 → lvcp.c)
  circuitpython_spike/    Phase 0 templates (copy into CP tree)
  circuitpython_emit_plan.md  CP emission phases and API mapping
  emit_micropython.py orchestrates analyze + emit_c
  generator.py        wires context, generation, metadata
  metadata.py         JSON export
  util.py             memoize, eprint

gen_mpy.py is kept only for regression testing (compare_bindings.sh). Production builds use gen_lv_bindings.py.

Verify generator parity

./lv_micropython_cmod/compare_bindings.sh

Compares gen_mpy.py vs gen_lv_bindings.py output (ignoring the command-line comment).

Full regression (MicroPython + CircuitPython)

./lv_micropython_cmod/verify_bindings.sh

Runs compare_bindings.sh, regenerate_lvcp.sh, and checks generated/lvcp.c size, metadata counts, LVCP_MODULE_GLOBALS, and absence of MP_REGISTER_MODULE.

MicroPython unix smoke test (after ./build_unix.sh):

./micropython/ports/unix/build-standard/micropython ./lv_micropython_cmod/test_lvgl_unix.py

CircuitPython unix smoke test (after ./build_cp_unix.sh with LVGL patched):

./circuitpython/ports/unix/build-coverage/micropython ./lv_micropython_cmod/test_lvgl_cp_unix.py

Covers init, headless display, widgets, event callbacks, and GC visibility (see binding/gc_callback_audit.md).

Before the first CircuitPython build, read binding/cp_flash_budget.md (flash partition headroom + allocator notes).

Builds

Script Port Notes
build_unix.sh micropython/ports/unix Desktop dev / testing
build_esp32.sh micropython/ports/esp32 Requires ESP-IDF
build_cp_unix.sh circuitpython/ports/unix Default VARIANT=coverage; stock or LVGL-patched tree

All MicroPython builds pass USER_C_MODULES pointing at this repo root and use manifest.py for frozen modules.

CircuitPython

Use a release tree, not Adafruit's main branch. After cloning, pin tag 10.2.1 on local branch circuitpython-10.2.1 (see first-time setup above). Leave the CP tree unpatched until you are ready to integrate LVGL; check status with:

./lv_micropython_cmod/apply_cp_lvgl_patches.sh --status

When ready to wire LVGL (default unix / standard port):

./lv_micropython_cmod/apply_cp_lvgl_patches.sh --apply

Primary target: CircuitPython unix port, coverage variant (desktop dev; avoids unix standard + ringio ringbuf mismatch on 10.2.1). Patches wire ports/unix/Makefile and variants/coverage/mpconfigvariant.mk.

Embedded target (later): ESP32-P4-Function-EV-Board (espressif_esp32p4_function_ev) — build_cp_esp32.sh (not yet implemented); patch with PORT=espressif BOARD=espressif_esp32p4_function_ev ./lv_micropython_cmod/apply_cp_lvgl_patches.sh --apply

Build glue and full emission live in lv_micropython_cmod/:

File Purpose
circuitpython.mk Port Makefile fragment (LVGL + allocator + lvcp.c)
apply_cp_lvgl_patches.sh Copy spike + patch CP tree (--dry-run / --apply)
circuitpython_board.snippet.mk Manual patch checklist (reference)
binding/gc_callback_audit.md GC roots and callback lifetime notes
binding/cp_flash_budget.md Flash/allocator review before first CP build
regenerate_lvcp.sh Preprocess + --target circuitpython → generated/lvcp.c
binding/circuitpython_emit_plan.md Phased API mapping from metadata
circuitpython_spike/ Hand-written module + merge docs for phase-1 entries

Current status:

  1. Phase 0 spike templates (shared-bindings/lvgl/, shared-module/lvgl/)
  2. Phase 1–7 emitter complete (max_phase: 7); lvcp.c ~39.5k lines (parity with lvmp.c)
  3. GC-aware allocator draft (lv_mem_core_circuitpython.c, via circuitpython.mk)
  4. Port wiring + on-tree build (apply_cp_lvgl_patches.sh → ./build_cp_unix.sh)
  5. Display bridge — ON HOLD (Python displayio/mipidsi flush/tick; resume when requested)

Regenerate and verify bindings:

./lv_micropython_cmod/regenerate_lvcp.sh
./lv_micropython_cmod/verify_bindings.sh

Build CircuitPython unix (works before or after patching; does not modify the CP tree):

./build_cp_unix.sh

On a clean release tree this builds stock CircuitPython. After patching, run regenerate_lvcp.sh first; the patched Makefile supplies CMODS_DIR and pulls in full LVGL + lvcp.c (make fails if bindings are missing). Each run starts with make clean.

After patching:

./lv_micropython_cmod/regenerate_lvcp.sh
./lv_micropython_cmod/apply_cp_lvgl_patches.sh --apply
./build_cp_unix.sh

Patch status: ./lv_micropython_cmod/apply_cp_lvgl_patches.sh --status (pending / patched / ok / missing). Defaults to PORT=unix VARIANT=coverage.

Display bridge is ON HOLD. C bindings do not include flush/tick; a future Python displayio bridge (similar to pydisplay_cmods on MicroPython) will be designed when you ask to resume that work.

The binding/ package supports --target circuitpython with max_phase: 7 for full API emission.