Backlight enable detection, I used the voltage detection of Lane0_P, when the EDP has a signal, the voltage is 0.5V, when the EDP has no signal, the voltage is 0V, MCU uses ADC detection, output high and low level signal control panel backlight.
Backlight brightness PWM, MCU detects keyboard FN+F9 and FN+F10 buttons, output PWM signal control panel brightness .
Modify BIOS VBT, modify with Intel BMP Utility tool, delete internal LVDS display, do not use clone mode, only one monitor, full UEFI mode works perfectly, external monitor works perfectly. The BIOS version I use is F.72, see VBT.ZIP file.
2K panel model: LQ125T1JX03C
Edp signal cable, I made it myself, the signal cable length is 13cm, the differential signal cable is twisted and twisted, covered with shielding tape.
DP_TO_EDP1.pdf
VBT.zip