uC – STM32U5G9NJH6Q
Display – 720 × 720 (ST7703 panel)
Display controller – ST7703
MIPI lanes – 2 lanes
DSI Host Mode – Video Mode (DSI_VID_MODE_BURST)
Pixel format – RGB888
Problem / Symptoms
After the initial display setup (LP mode initialization sequence), the backlight turns ON, but no image is displayed on the LCD.
I have verified that the MIPI DSI clock and data line waveforms are present and active on the scope — both lanes appear to be toggling correctly.
Despite proper DSI signal activity, the panel remains blank (black screen), and there is no visible frame output from TouchGFX.
What I have verified/working
I can communicate with the display over DSI and run the initialization sequence (LP command mode) — panel responds, backlight comes on.
LTDC timings & basic parameters match the panel spec and st7703.c values (see below).
PHY frequency configured around panel-recommended range (450–510 MHz / VCO ~800 MHz–1 GHz).
TouchGFX / display driver configured to disp_ltdc. dma_2d and gpu2d acceleration enabled. vsync source set to LTDC.
Backlight PWM and reset GPIO working.
My LTDC configuration (current)
Resolution: 720 × 720 (active) — matches ST7703.
Pixel Format: RGB888.
Porch & sync (approx / set to values close to st7703.c):
HSync = 6, HBP ≈ 51, HFP ≈ 51 (I used HSync=6, HBP=3 earlier while calculating HorizontalLine = 1452 — verified active + porches match).
VSync = 2–3, VBP ≈ 12, VFP ≈ 12–15.
Layers: 1. Buffering strategy: Single at present (I can switch to double).
DSI Host settings
Mode: DSI_VID_MODE_BURST (continuous video).
Lanes: DSI_TWO_DATA_LANES.
LP command mode: enabled (to send DCS commands like DISPLAY ON).
PHY frequency: set to panel-recommended range.
LP mode enabled for porch/sync intervals (low power during those phases).
HorizontalLine computed appropriately for active + porches + sync (e.g. ~1452 for current timing).
TouchGFX
Display interface: disp_ltdc.
Buffering: Single (considering Double).
Hardware accel: dma_2d, gpu2d_enabled.
VSYNC source: vsync_ltdc.
Backlight / Reset
Has anyone successfully run TouchGFX with DSI Video Mode (burst) on an ST7703 panel (RGB888 / 2-lane)? If yes, could you share example project or configuration highlights?
