Revert "Tune SSD1677 LUTs for PaperMono text/quality modes" (#272) - #275
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This reverts merge commit 1f481eb (PR m5stack#272, commit 3bcad74). The retuned epd_quality waveform is not DC balanced: every gray level nets +58 to +72 frames of VSH1 per refresh, whereas the previous waveform nets zero for all four levels. On the panel this shows up as sticking after repeated quality refreshes, and the white level ends up slightly gray. The new epd_text waveform also reduced that mode from four gray levels to two, dropping light details in images. Withdrawn in agreement with the author. The issue that motivated the change (white areas developing dark speckles after prolonged use, which clear on the next refresh) will be investigated separately.
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Summary
Reverts #272 (merge commit 1f481eb) and restores the previous
epd_quality/epd_textwaveforms for the SSD1677 (PaperMono). Withdrawn in agreement with the author of #272.Why
Verified on a PaperMono against the current
develop:lut_qualityis not DC balanced. Summing VSH1/VSL frames over one refresh per gray level gives a net drive of +58 (white) to +72 (black) frames of VSH1. The previous waveform nets exactly zero for all four levels. On the panel this shows up as sticking after repeated quality refreshes; switchinglut_qualityback to the previous table on the same build removes it.lut_textis a binary GC1 waveform, soepd_textdropped from four gray levels to two and light details in images are lost.The vendor waveform that #272 ported was validated in a standalone test program that leaves the panel's gate/source/VCOM voltages at their OTP defaults and powers the analog section down after every update. M5GFX applies explicit voltages from the LUT tail, so the two environments are not equivalent and the vendor's soak result does not carry over as-is.
The issue that motivated #272 (white areas developing dark speckles after prolonged use, recovering on the next refresh) is not addressed here and will be investigated separately.
Changes
Panel_SSD1677.cpp: restore the previouslut_qualityandlut_text, remove_refresh_mode1_text, routeepd_textback through_refresh_mode1_absolutePanel_SSD1677.hpp: remove the_refresh_mode1_textdeclarationPure revert; no other changes.