[META] LPC8xx end-to-end support: orchestrator + Arduino framework + real FastLED sketches

[zackees]

Goal

Drive the NXP LPC8xx family (initial targets: LPC845, LPC804) from "the CI workflow is stubbed to pass" to "FastLED sketches build, link, flash, and blink." This is the umbrella tracking the multi-stage work; individual stages have their own issues + PRs.

Why a META

Three pieces are required and they're independently sized (one is in this repo, one is in a separate repo, one is a board-bring-up matrix). Filing as a meta so the work doesn't drift between issues, and so anyone looking at the LPC8xx status can see the whole staircase at once.

Current state (as of filing)

• Stage 0 — scaffolding: ✅ DONE

  • Platform::NxpLpc enum + string parsing (fbuild-core)
  • Board JSON: lpc845.json, lpc804.json (fbuild-config)
  • Linker scripts + startup .S for both MCUs (fbuild-build/src/nxplpc/assets/)
  • Shared MCU config (nxplpc.json)
  • ARM toolchain pre-install hook
  • Dispatch wiring: NxpLpcPlatformSupport → NxpLpcStubOrchestrator
  • CI workflows stubbed to pass (PR ci(lpc8xx): stub Build LPC804 / LPC845 workflows so they pass #476)

• Stage 1 — Arduino framework repo: ✅ DONE (skeleton)

  • zackees/ArduinoCore-LPC8xx created, BSD-3-Clause
  • Directory layout: cores/lpc8xx/ (Arduino.h, wiring_*, HardwareSerial, SPI, main.cpp) + variants/{lpc845,lpc804}/ + examples/Blink/
  • All bodies are TODO no-op stubs; substrate = NXP MCUXpresso SDK

Open sub-issues

• Stage 2: implement NXP LPC8xx build orchestrator (replace stub, unstub LPC804/LPC845 CI) #477 — Stage 2: build orchestrator
  Replace NxpLpcStubOrchestrator with a real build() that produces firmware.elf + firmware.bin for the empty .ino fixtures. Pattern: copy fbuild-build/src/teensy/. Independent of Arduino-compatible framework for NXP LPC8xx (search existing, fork, or polyfill) #479 — works against the stub main.cpp shim that's already in nxplpc/. Unblocks unstubbing the CI workflows.

• Arduino-compatible framework for NXP LPC8xx (search existing, fork, or polyfill) #479 — Stage 3: Arduino framework implementation
  Fill in the no-op stubs in ArduinoCore-LPC8xx against the MCUXpresso SDK. Estimated ~500–800 LOC C/C++. Decision recorded on Arduino-compatible framework for NXP LPC8xx (search existing, fork, or polyfill) #479. Verification needs hardware (LPC845-BRK / LPCXpresso804).

• Stage 4: vendor the framework into fbuild
  Once the polyfill has working code, add crates/fbuild-packages/src/library/lpc8xx_core.rs mirroring teensy_core.rs. Switch lpc845.json / lpc804.json to frameworks: ["arduino"]. Delete Stage 2: implement NXP LPC8xx build orchestrator (replace stub, unstub LPC804/LPC845 CI) #477's hand-rolled main.cpp shim in favor of ArduinoCore-LPC8xx's framework-owned main().

• Stage 5: real test fixtures
  Replace the empty tests/platform/lpc845/lpc845.ino and tests/platform/lpc804/lpc804.ino stubs with real Blink sketches calling pinMode + digitalWrite + delay.

• Stage 6: FastLED canary
  Blink, DemoReel100, FxEngine compile clean for both LPC845 and LPC804 via fbuild build. This is the issue-Arduino-compatible framework for NXP LPC8xx (search existing, fork, or polyfill) #479 acceptance criterion.

• Stage 7: deploy support
  lpc21isp / pyocd / cmsis-dap / jlink wiring. Tracked separately when the rest is done.

• Stage 8: unstub CI workflows
  Revert .github/workflows/build-lpc845.yml and build-lpc804.yml to the template_build.yml caller form (restore via git show ac6b72d5^:...). The PR ci(lpc8xx): stub Build LPC804 / LPC845 workflows so they pass #476 stubs were always a temporary patch.

Ordering

Stages 2 and 3 can land in parallel — #477 produces an ELF using the hand-rolled main.cpp; #479 produces a framework that, once done, replaces that shim. Stage 4 is the integration point; Stages 5–8 follow.

Related

• Stage 2: implement NXP LPC8xx build orchestrator (replace stub, unstub LPC804/LPC845 CI) #477, Arduino-compatible framework for NXP LPC8xx (search existing, fork, or polyfill) #479 (sub-issues)
• Agent tool with isolation: "worktree" stacks worktrees inside existing worktree sandbox #485 (unrelated, but referenced because it's the harness-side issue that kept biting LPC8xx sub-agents during research)
• PR ci(lpc8xx): stub Build LPC804 / LPC845 workflows so they pass #476 (the CI stubs being replaced)
• PR refactor(symbol_analyzer): split into mod/markdown/tests submodule #475, refactor(symbol_analysis): split graph.rs + fix rustdoc broken link #474 (LOC-gate split work that unblocked CI for docs(bloat): pin map-file tombstone trap with regression test + doc note #471 — also unrelated to LPC8xx itself but landed during the same window)
• zackees/ArduinoCore-LPC8xx (the external framework repo)
• meta: port FastLED to NXP LPC8xx (LPC804 + LPC845) — two-stage plan FastLED#2836 (the FastLED-side umbrella)

[zackees]

Status check-in:

• Stage 1 (Arduino framework repo) — zackees/ArduinoCore-LPC8xx created and seeded with BSD-3-Clause skeleton (cores + variants for LPC845/LPC804 + Blink example). All bodies are TODO stubs pointing at MCUXpresso SDK call sites. No implementation yet — that's Stage 3 / Arduino-compatible framework for NXP LPC8xx (search existing, fork, or polyfill) #479 follow-up.
• Stage 2 (build orchestrator) — PR feat(nxplpc): real Stage-2 build orchestrator (#477, part of #487) #488 opened (this is Stage 2: implement NXP LPC8xx build orchestrator (replace stub, unstub LPC804/LPC845 CI) #477 done). NxpLpcStubOrchestrator replaced with a real NxpLpcOrchestrator following the Apollo3 pattern; embedded main.cpp shim materialised at compile time so the empty .ino test fixtures link. 18/18 nxplpc tests green. Awaiting CI.

Once #488 merges:

• Stage 8 (unstub CI workflows) becomes the natural immediate follow-up.
• Stage 3 (Arduino-compatible framework for NXP LPC8xx (search existing, fork, or polyfill) #479) and Stage 4 (vendoring) can proceed in parallel; Stage 5 + 6 follow Stage 4.