Framebuffer Dump

Dump the current STM32 LCD framebuffer via J-Link and convert it to PNG for visual comparison with Figma. Use when user asks to export, snapshot, dump, or capture what is currently displayed on device screen.

Framebuffer Dump (J-Link → PNG)

Export the actual on-device rendered frame directly from SDRAM framebuffer and convert to PNG.

Default parameters (PRO2)

• Device: STM32H747XI_M7
• FB base: 0xD0000000
• Resolution: 604x1024
• Pixel format: RGB888 (3 bytes/pixel)
• Dump size: 604*1024*3 = 1,855,488 (0x1C5000)

One-shot workflow

1) Create J-Link command file

Use scripts/dump_fb.jlink.template and replace placeholders:

• {{DEVICE}}
• {{SPEED_KHZ}} (e.g. 12000)
• {{OUT_BIN}} (absolute path)
• {{FB_ADDR}} (e.g. 0xD0000000)
• {{FB_SIZE}} (e.g. 0x1C5000)

2) Dump raw framebuffer

JLinkExe -NoGui 1 -CommandFile /tmp/jlink_dump_fb.jlink > /tmp/jlink_dump_fb.log 2>&1

3) Convert raw to PNG

python3 scripts/dump_fb.py \
  --in /path/to/fb_dump.bin \
  --out /path/to/fb_dump_604x1024.png \
  --width 604 --height 1024 --stride 3

Troubleshooting

• If output bin is 0 bytes: check J-Link connection / path permissions.
• If colors look wrong: verify pixel format is RGB888 (not BGR / RGB565).
• If image shifted/corrupt: verify width/height match current display mode.
• If command hangs too long: make sure dump size is correct (0x1C5000 for 604x1024 RGB888).

Notes

• This method captures real framebuffer pixels (no camera distortion).
• Best for Figma-vs-device pixel comparison and regression snapshots.