Andrew c

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6 years, 11 months ago.

Confusion about PwnOut class

I am super confused how the pwm class works.

The first program is from the PwmOut referance file:

LED_Fade

// Fade a led on.
#include "mbed.h"

PwmOut led(LED1);

int main() {
    while(1) {
        led = led + 0.01;
        wait(0.2);
        if(led == 1.0) {
            led = 0;
        }
    }
}

Base o the previous example I wrote this next program, that should act similar to the previous program, but for some reason it is backwards (adding to led dims LED1, subtracting from led brightens LED 1):

Control LED brightness using keyboard

//Author: collinan
//Control LED brightness using keyboard
//Tested on FRDM-KL46Z (using Terminal, on MacBook pro)
//'u' for brightness up
//'d' for brightness down
//Program compiles
#include "mbed.h"

Serial pc(USBTX , USBRX);//tx, rx
PwmOut led(LED1);

int main()
{
    led=0;
    while (1) {

        pc.printf("Press 'u' to brighten LED1, and 'd' to dim LED1 \n\r");
        char c = pc.getc();//get user input

        //this "if" should brighten but it dims LED
        if((c == 'u')) {
            pc.printf("IN Bright\n\r");
            if(led!=1) {
                led =led + 0.1;
            } else {
                pc.printf("Max reached.\n\r");
            }
        }

        //this "if" should dim but it brightens LED
        if((c == 'd') ) {
            pc.printf("IN Dim\n\r");
            if(led!=0) {
                led =led - 0.1;
            } else {
                pc.printf("Min reached.\n\r");
            }
        }
    }
}

Any explanation wold be appreciated. Thanks in Advance.

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