Tighten F469I-DISCO dual-panel init: NT35510 timing alignment and detection-path documentation

[Copilot]

PR stm32-rs#843 adds runtime LCD controller detection for STM32F469I-DISCO board revisions (OTM8009A on older boards, NT35510 on B08+). This update hardens that path by aligning NT35510 timing/delay behavior with known-good references and documenting the key design decisions in code.

• NT35510 LTDC timing updated to conservative, validated values

  • In examples/f469disco-lcd-test.rs, NT35510_DISPLAY_CONFIG vertical timings were changed to:
    • v_sync: 120
    • v_back_porch: 150
    • v_front_porch: 150
  • This replaces the smaller values and matches the proven NT35510 profile used in ST/specter-derived implementations.

• NT35510 power-on sequencing clarified and tightened

  • In examples/f469disco/nt35510.rs, post-DISPON (0x29) wait increased from 10ms to 20ms.
  • Added inline sequencing notes for SLPOUT/DISPON timing expectations.

• Detection/runtime compatibility rationale made explicit

  • Added concise in-code documentation for:
    • Board revision split reference (UM1932 context),
    • Why runtime detection continues to use RDID1-based flow,
    • Why DSI_LP_SIZE/DSI_VLP_SIZE = 64 is retained for one binary targeting both panel variants,
    • Why reset pin is driven push-pull in the shared path.

pub const NT35510_DISPLAY_CONFIG: DisplayConfig = DisplayConfig {
    active_width: 480,
    active_height: 800,
    h_back_porch: 34,
    h_front_porch: 34,
    v_back_porch: 150,
    v_front_porch: 150,
    h_sync: 2,
    v_sync: 120,
    frame_rate: 60,
    h_sync_pol: true,
    v_sync_pol: true,
    no_data_enable_pol: false,
    pixel_clock_pol: true,
};

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.