[IDEA] [Tut] How to turn off Backlight of a Waveshare 7" HDMI LCD using GPIO and screensaver

[newto]

I found this post and have made a few improvements/modifications

The version of the Waveshare 7" I have had a capacitor to ground just below the removed resistor (see attached photo) connected to the Enable pin of the the LED controller, I removed this as well to get a proper PWM signal to the enable pin, otherwise it becomes a triangle wave. Also, if you're using a raspberry pi, you don't need to add another ground, the panel is already grounded through the USB and HDMI cables.



Also, I used pigpio instead of wiring pi, gpioHardwarePWM(18, 1000, 1000000) means to use BCM pin 18 (pin 12 on the PI), at 1000Hz (from the 4103 manual), and 1000000 is 100% duty factor, and 500000 would be a 50% duty factor.

The attached code cycles back and forth between 100% on and 50% on, I was using it to test power consumption changes.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>

#include <pigpio.h>


int main(int argc, char *argv[])
{

    if (gpioInitialise()<0) return 1;

    for (int h = 0; h<30; h++){
        printf("%d",gpioHardwarePWM(18, 1000, 1000000));
        printf("\n%d\n",1000000);
        gpioDelay(5000000);
        printf("%d",gpioHardwarePWM(18, 1000, 500000));
        printf("\n%d\n",500000);
        gpioDelay(5000000);
    }
    gpioTerminate();
}