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// PIC12F675 Configuration Bit Settings
#pragma config FOSC = INTRCIO   // INTOSC oscillator: I/O function on GP4/OSC2/CLKOUT, GP5/OSC1/CLKIN)
#pragma config WDTE = OFF       // WDT disabled
#pragma config PWRTE = ON       // PWRT enabled
#pragma config MCLRE = ON       // GP3/MCLR pin function is MCLR
#pragma config BOREN = ON       // BOD enabled
#pragma config CP = OFF         // Program Memory code protection is disabled
#pragma config CPD = OFF        // Data memory code protection is disabled
 
#include <xc.h>
#include <stdint.h>
 
#define _XTAL_FREQ 4000000U
#define STEP_DELAY_MS 20000U
 
#define STARTUP_PATTERNS 2U
#define REGULAR_PATTERNS 3U
#define TOTAL_PATTERNS (STARTUP_PATTERNS + REGULAR_PATTERNS)
 
// Fan transistor controls on GPIO 2/4/5
const uint8_t pattern[TOTAL_PATTERNS] = {
    // First two are the gentle startup
    0b000000, 0b000100,
    // These are the regular repeating pattern
    0b010100, 0b110000, 0b100100
};
 
// For shutting down the old fan *before* turning on the new
const uint8_t prePattern[TOTAL_PATTERNS] = {
    0b000000, 0b000000,
    0b000100, 0b010000, 0b100000
};
 
// Set GPIO 2/4/5 as digital outputs 
void setup(void) {
    
    ANSEL = 0;
    CMCON = 7;
    TRISIO = 0b001011;
    
}
 
void main(void) {
    
    uint8_t currentStep = 0;
    
    setup();
    
    for ( ; ; ) {
        
        // This will take long enough to ensure the transistor response
        GPIO = prePattern[currentStep];
        
        GPIO = pattern[currentStep];
        
        __delay_ms(STEP_DELAY_MS);
        
        ++currentStep;
        if (TOTAL_PATTERNS == currentStep) {
            // Cycle through regular patterns only
            currentStep = STARTUP_PATTERNS;
        }
    
    }    
    
    return;
}