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, plus BSPs for DEV190806042, FK743M5-XIH6, and STM32H7_CORE. Enables tear‑free double buffering, VSYNC‑synced flush, and DMA2D‑accelerated partial updates.

• New Features

  • st_ltdc.LTDC MicroPython driver: display timings, polarity, RGB565/RGB888/ARGB8888, DIRECT/FULL/PARTIAL modes.
  • Framebuffer set write‑through via MPU; AXI QoS tuned to avoid LTDC starvation.
  • touch_i2c.TP for GT9xx (GT911) via hardware I2C or SoftI2C.
  • Board BSPs configure PLL3 pixel clock and GPIOs; build auto-selects by BOARD.
  • Helpers and config: boards.py, panels.py, display_conf.py, st_ltdc_utils.py, display_driver.py; LVGL lv_conf.h added; examples/advanced_demo.py updated.

• Migration

  • Set BOARD and BOARD_VARIANT for the build; choose PANEL if needed; build with LVGL enabled.
  • In your app: from display_driver import disp, touch (one‑line init).
  • For custom hardware, add entries in boards.py and panels.py.

^{Written for commit 54f0af9. 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]

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.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At driver/stm32/st_ltdc/modules/st_ltdc.c, line 482:

<comment>`deinit()` lacks an initialization-state guard and unconditionally calls LTDC HAL operations, allowing out-of-sequence calls to operate on an uninitialized `hltdc` handle.</comment>

<file context>
@@ -0,0 +1,629 @@
+    }
+    // Blank the layer (alpha=0) so the panel goes dark without stopping clocks.
+    // Use NoReload + VBL reload to avoid tearing on the final frame.
+    HAL_LTDC_SetAlpha_NoReload(&hltdc, 0, LTDC_LAYER_1);
+    HAL_LTDC_Reload(&hltdc, LTDC_RELOAD_VERTICAL_BLANKING);
+    if (HAL_LTDC_DeInit(&hltdc) != HAL_OK) {
</file context>

[cubic-dev-ai]

P2: LTDC timing and geometry inputs are not range-validated, allowing unsigned underflow/wrap in register calculations.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At driver/stm32/st_ltdc/modules/st_ltdc.c, line 520:

<comment>LTDC timing and geometry inputs are not range-validated, allowing unsigned underflow/wrap in register calculations.</comment>

<file context>
@@ -0,0 +1,629 @@
+                                ? LTDC_PCPOLARITY_IPC   // inverted
+                                : LTDC_PCPOLARITY_IIPC; // not inverted
+    // Horizontal timing
+    hltdc.Init.HorizontalSync     = self->hsync - 1;
+    hltdc.Init.AccumulatedHBP     = self->hsync + self->hbp - 1;
+    hltdc.Init.AccumulatedActiveW = self->hsync + self->hbp + self->width - 1;
</file context>

[cubic-dev-ai]

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.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At driver/stm32/st_ltdc/modules/st_ltdc.c, line 264:

<comment>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.</comment>

<file context>
@@ -0,0 +1,629 @@
+    // NULL and returns without dereferencing freed memory.
+    MP_STATE_PORT(current_ltdc_obj) = MP_OBJ_NULL;
+
+    ltdc_display_obj_t *self = m_new_obj(ltdc_display_obj_t);
+    self->base.type = type;
+
</file context>

[cubic-dev-ai]

P2: Unsupported BOARD/VERSION/PANEL values can leave board/panel undefined, causing runtime import failure instead of a clear configuration error.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At driver/stm32/st_ltdc/display_conf.py, line 13:

<comment>Unsupported BOARD/VERSION/PANEL values can leave `board`/`panel` undefined, causing runtime import failure instead of a clear configuration error.</comment>

<file context>
@@ -0,0 +1,26 @@
+except ImportError:
+    PANEL = "IPS1024x600"
+
+if BOARD == "STM32H7_CORE":
+    if VERSION == "V10":
+        from boards import STM32H743_CORE_V10 as board
</file context>