Add LTDC display and GT911 touch drivers for STM32H7 boards

[nuraci]

Summary

Add a generic LTDC display driver and GT911 I2C touch driver for STM32H7,
along with board-specific BSP files for three boards (DEV190806042,
FK743M5-XIH6, STM32H7_CORE).

LTDC driver (driver/stm32/st_ltdc/)

• st_ltdc.c — MicroPython C module exposing the st_ltdc.LTDC class:
  configurable timing parameters, polarity flags, RGB565/RGB888/ARGB8888
  color formats, double-buffered VSYNC-synced flush (DIRECT/FULL mode)
  and DMA2D-accelerated partial updates (PARTIAL mode).
  Framebuffer MPU region is configured as Write-Through so LTDC reads
  are always coherent without manual cache maintenance.
  AXI QoS priorities are tuned to prevent LTDC starvation.
• touch_i2c.c — MicroPython C module exposing touch_i2c.TP class
  for GT9xx touch controllers, supporting both hardware I2C and SoftI2C.
• Python layer — st_ltdc_utils.py (init helper), boards.py (pin
  configs per board), panels.py (display timing presets), display_conf.py
  (auto-selects board/panel from build config), display_driver.py
  (one-line boot).

Board-specific BSP (driver/stm32/{BOARD}/bsp_ltdc.c)

Each file implements HAL_LTDC_MspInit() / HAL_LTDC_MspDeInit() with
the correct PLL3 pixel-clock setup and GPIO alternate-function mapping
for that board's LTDC wiring. The build system (micropython.mk)
automatically picks the right BSP based on the BOARD variable.

Supported configurations

Board	Display	Touch	I2C
DEV190806042	RGB 24-bit (Port I/J/K)	GT911	SoftI2C
FK743M5-XIH6	RGB 24-bit (mixed ports)	GT911	SoftI2C
STM32H7_CORE V1.0	RGB (scattered pins)	GT911	HW I2C4
STM32H7_CORE V1.3	RGB (scattered pins)	GT911	SoftI2C

Test plan

• Build with LVGL enabled for each board variant
• Verify display initializes and shows LVGL content without flickering
• Verify touch input works (GT911 detected, coordinates reported)
• Verify double-buffered DIRECT mode (no tearing)
• Verify PARTIAL render mode with DMA2D
• Test soft-reset cycle (Ctrl-D): display deinits cleanly and reinits
• Test lv.deinit() / lv.init() cycle without crash

Boards docs and photos

https://github.com/Copper-And-Code/stm32h7-boards-docs

micropython sample code and tools

https://github.com/Copper-And-Code/lv_micropython_code_and_tools

---

Summary by cubic

Add a generic LTDC display driver and GT911 I2C touch driver for STM32H7 boards with LVGL integration. Adds BSPs for DEV190806042, FK743M5-XIH6, and STM32H7_CORE, plus safer init/deinit and config validation.

• New Features

  • st_ltdc.LTDC driver: configurable timings/polarity, RGB565/RGB888/ARGB8888, tear‑free double buffering with VSYNC‑synced flush, DMA2D‑accelerated partial updates.
  • Framebuffer set write‑through via MPU; AXI QoS tuned to avoid LTDC starvation.
  • touch_i2c.TP for GT9xx (GT911) via hardware I2C or SoftI2C; BSPs and auto board/panel selection via boards.py/panels.py/display_conf.py; display_driver.py for one‑line init; LVGL lv_conf.h; example updated.

• Bug Fixes

  • Zero‑initialize the display object to avoid picking the wrong backlight path; guard deinit() when the handle was never initialized.
  • Validate panel timings (width/height/hsync/vsync) and raise ValueError for unsupported BOARD/VERSION/PANEL in display_conf.py.

^{Written for commit b6fce8e. Summary will update on new commits.}

[cubic-dev-ai]

4 issues found across 14 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="driver/stm32/st_ltdc/modules/st_ltdc.c">

<violation number="1" location="driver/stm32/st_ltdc/modules/st_ltdc.c:264">
P2: Backlight selector fields are not fully initialized before use, so init/deinit may read indeterminate `bl_pin`/`bl_led` values and take the wrong backlight path.</violation>

<violation number="2" location="driver/stm32/st_ltdc/modules/st_ltdc.c:482">
P2: `deinit()` lacks an initialization-state guard and unconditionally calls LTDC HAL operations, allowing out-of-sequence calls to operate on an uninitialized `hltdc` handle.</violation>

<violation number="3" location="driver/stm32/st_ltdc/modules/st_ltdc.c:520">
P2: LTDC timing and geometry inputs are not range-validated, allowing unsigned underflow/wrap in register calculations.</violation>
</file>

<file name="driver/stm32/st_ltdc/display_conf.py">

<violation number="1" location="driver/stm32/st_ltdc/display_conf.py:13">
P2: Unsupported BOARD/VERSION/PANEL values can leave `board`/`panel` undefined, causing runtime import failure instead of a clear configuration error.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

1 issue found across 2 files (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="driver/stm32/st_ltdc/modules/st_ltdc.c">

<violation number="1" location="driver/stm32/st_ltdc/modules/st_ltdc.c:470">
P1: `deinit()` can become a no-op after LVGL display delete because it keys off a global that is cleared outside `deinit`, skipping LTDC/backlight teardown.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[nuraci]

The CI failure is unrelated to this PR — it's a pre-existing issue in the ESP32 port. This PR only touches STM32 board definitions and the LTDC driver.