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fix(waveshare-c5-35): start the display dark, no static at boot - #3067
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slickrick773 wants to merge 1 commit into
Open
slickrick773 wants to merge 1 commit into
slickrick773 wants to merge 1 commit into
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The expander init lit the backlight at full before the display was initialised, so the panel's own memory was visible at boot: random static after power-on, the previous picture after reset. Leave the backlight off in the expander init. The core already sets the brightness from begin_tft(), after the boot screen has been drawn, so that becomes the first light-up. The ordering follows the "Clean startup" notes in ESP32-C5-BSP (slickrick773/ESP32-C5-BSP). Checked on the board with 240 fps video: reset and cold boot both go from dark straight to the boot screen.
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Proposed Changes
On the Waveshare ESP32-C5-Touch-LCD-3.5 the I/O expander init turned the backlight on at full before
tft.init(). For a moment at boot the panel showed its own memory: random static after power-on, the previous screen after a reset.This removes that early backlight write. The core already calls
setBrightness()frombegin_tft()after the "Booting" screen is drawn, so that becomes the first light-up.One line removed in
boards/waveshare-c5-35/interface.cpp, plus a comment. No core changes, no other boards.Types of Changes
Bugfix (board-specific, cosmetic).
Verification
Flash
waveshare-c5-35, then press RST and power-cycle. Before: a flash of static or the old screen. After: dark, then the boot screen.Testing
Built on current
devand hardware-tested on the board with 240 fps video of a reset and a cold boot; both go from dark straight to the boot screen. Four logged boots reached the main menu. No unit test (display timing).Linked Issues
Follow-up to the board's original port. Root cause and ordering are written up in my board support package for these boards: https://github.com/slickrick773/ESP32-C5-BSP (docs/BOARD-WS-C5-35.md, "Clean startup").
User-Facing Change
Further Comments
About a second of blank glow right after power-on comes before any firmware runs and is not something firmware can remove.