LCD Backlight Error => Solved

eschoi@huvitz.c · Posted at 9/4/2018 13:45:08

Last edited by eschoi@huvitz.c In 9/5/2018 19:00 Editor

I am working with AIO-3399J and DM-M10R800
I compiled with rk3399-firefly-aio-linux-lvds.dts
and I checked lcd_pwr_en is high , VDD-CORE is 1.2V , lcd_rst is high, 1.8V
and I checked LCD Board VGH =>5.59V , VGL=>-5.6V
AVDD=>11.2V ,VCC_LCD=>3.2V, LED+ => 4.97V, LED- =>0.0V
But LCD backlight is not working. tured off.
what position should I check?
I want to turn on LCD

eschoi@huvitz.c · Posted at 9/5/2018 18:52:45

Last edited by eschoi@huvitz.c In 9/6/2018 10:00 Editor

<Solved>
1.edit rk3399-firefly-aio-linux-lvds.dts
      backlight: backlight {
            status = "okay";
            compatible = "pwm-backlight";
            pwms = <&pwm0 0 25000 1>;
            brightness-levels = </*
                        0 1 2 3 4 5 6 7
                        <SKIP>
                     248 249 250 251 252 253 254 255>;
            default-brightness-level = <200>;  => default-brightness-level = <100>;
2.check LED+ of LCD Board
LED+ voltalge should be higher than 11v
when  default-brightness-level is 200,  78% duty, LED+ voltage is 4.9v  => backlight turned off
but if default-brightness-level is 100,  40% duty,LED+ voltage is 11.4v  => backlight turned on

Success!!!!!!!!