Hello,
I use the recommended function from the examples-folder to
adjust the brightness of the LCD backlight:
But setting the value to zero keeps the brightness at nearly 50%. Why isn't
it possible to set the duty cycle of the PWM according to brightness-value
(0 to 0% .. 255 to 100%), what means a value of 0 will shut off the backlight?
Kind regards,
Reimar
For me, that does work (except that I write to /sys/class/backlight/pwm-backlight/brightness but it is the same file).
Are you sure your backlight can go below 50% brightness ?
We are using an LED backlight that can go all the way down to nothing but we used to use a CFL backlight and even with 0% duty PWM it would not go below a certain level of brightness (appeared to be around 50%).
You should be able to turn the backlight off with xset s [time] if using Xwindows, or echo "1" >/sys/class/backlight/pwm-backlight/bl_power
Hope this helps...
Hello,
not all backlights can be dimmed down to 0%. For example some ccfl lamps are dimmable only down to 20 %.
And some backlight inverters have a separete pin to shutdown the inverter ( backlight off ).
Thanks for your responses,
the problem is solved.
You were right, the voltage of the LED-background (it was a LED no CCFL), is nearly at 0V (150mV), when the PWM-value is 0. This residual voltage was sufficient to let the background LED glow at (maybe) 15-20%.
