PWMfanController.c

/*This code for a PIC12F615 compiles in mikroC for PIC http://www.mikroe.com
It takes an analog value from a dash-mounted potentiometer and drives a MOSFET proportional to the input.  The MOSFET pulses the low-side of a blower motor in 
a 1997 Mitsubishi Mirage, providing 128 speeds*/



void main() {
     int anin=0, ramped=255;
      unsigned long temp = 0;

      TRISIO   = 0x01; //set GPIO0 as input
      ANSEL   = 0x01; //use AN0 (0C for 2 and 3
      //C1ON_bit = 0;
      //GPIO = 0x00;

      PWM1_Init(18000);
      PWM1_Set_Duty(0);

      PWM1_Start();


      Delay_ms(1000);          //Delay fan startup

      while(1) {

               PWM1_Set_Duty(ramped);

               temp = ADC_Read(0);      //Read in 10-bit analog value
               anin = temp >> 3;               //Shift the 10-bit value to only 7 bits
                                               //and store in a 1-byte variable

               anin += 0b10000000;              //Add offset so anin is between 128 and 255

               if (anin<ramped) {
                ramped-=1;      //If desired (anin) is low, decrement ramped
               }
               if (anin>ramped) {
                ramped+=1;        //If desired (anin) is higher, increment ramped
               }

               PWM1_Set_Duty(ramped);
               Delay_ms(20);           //slow down the ramping
      }
}