PIC12F1822 - Fade an LED in and out

03.01.25

Embedded

This program fades an LED in and out. The LED is connected to RA4.

// INCLUDE LIBRARIES
#include < xc.h >

// CONFIGURATION BITS
// CONFIG1
#pragma config FOSC     = INTOSC    // Oscillator Selection (INTOSC oscillator: I/O function on CLKIN pin)
#pragma config WDTE     = OFF       // Watchdog Timer Enable (WDT enabled)
#pragma config PWRTE    = OFF       // Power-up Timer Enable (PWRT disabled)
#pragma config MCLRE    = ON        // MCLR Pin Function Select (MCLR/VPP pin function is MCLR)
#pragma config CP       = OFF       // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config CPD      = OFF       // Data Memory Code Protection (Data memory code protection is disabled)
#pragma config BOREN    = ON        // Brown-out Reset Enable (Brown-out Reset enabled)
#pragma config CLKOUTEN = OFF       // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)
#pragma config IESO     = ON        // Internal/External Switchover (Internal/External Switchover mode is enabled)
#pragma config FCMEN    = ON        // Fail-Safe Clock Monitor Enable (Fail-Safe Clock Monitor is enabled)

// CONFIG2
#pragma config WRT      = OFF       // Flash Memory Self-Write Protection (Write protection off)
#pragma config PLLEN    = ON        // PLL Enable (4x PLL enabled)
#pragma config STVREN   = ON        // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will cause a Reset)
#pragma config BORV     = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), low trip point selected.)
#pragma config DEBUG    = OFF       // In-Circuit Debugger Mode (In-Circuit Debugger disabled, ICSPCLK and ICSPDAT are general purpose I/O pins)
#pragma config LVP      = ON        // Low-Voltage Programming Enable (Low-voltage programming enabled)

#define _XTAL_FREQ 4000000          // Reference frequency for the compiler
#define led PORTAbits.RA4           // Assign the LED to RA4

void main(void) {
    // Configure RA4 as output
    TRISA4 = 0;     // Set RA4 as output
    ANSA4 = 0;      // Disable analog input on RA4
    led = 0;        // Initialize RA4 to low
    
    OSCCONbits.IRCF = 0b1101;   // Internal oscillator set to 4MHz
    
    unsigned char brightness = 0;
    unsigned char direction = 1;    // 1 for increasing, 0 for decreasing

    while (1) {
        for (int i = 0; i < 255; i++) {
            if (direction) {
                brightness++;
            } else {
                brightness--;
            }
            
            // Apply PWM manually
            for (int j = 0; j < 255; j++) {
                if (j < brightness) {
                    led = 1;
                } else {
                    led = 0;
                }
                __delay_us(10); // Short delay for pseudo-PWM cycle
            }
        }
        
        // Reverse direction at max or min brightness
        if (brightness == 255 || brightness == 0) {
            direction = !direction;
        }
    }
}

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