Embedded Systems Design with the Atmel AVR Microcontroller Part II

162 CHAPTER 6. TIMING SUBSYSTEM
Open_Speed_int = ReadADC(0x03);
//Open Speed Setting unsigned int
//Convert to max duty cycle setting
//0 VDC = 50% = 127, 5 VDC = 100% =255
Open_Speed_float = ((float)(Open_Speed_int)/(float)(0x0400));
//Convert volt to PWM constant 127-255
Open_Speed_int = (unsigned int)((Open_Speed_float * 127) + 128.0);
//Configure PWM clock
TCCR1A = 0xA1;
//freq = resonator/510 = 10 MHz/510
//freq = 19.607 kHz
TCCR1B = 0x01; //no clock source division
//Initiate PWM duty cycle variables
PWM_duty_cycle = 0;
OCR1BH = 0x00;
OCR1BL = (unsigned char)(PWM_duty_cycle);//Set PWM duty cycle CH B to 0%
//Ramp up to Open Speed in 1.6s
OCR1BL = (unsigned char)(PWM_duty_cycle);//Set PWM duty cycle CH B
while (PWM_duty_cycle < Open_Speed_int)
{
if(PWM_duty_cycle < Open_Speed_int) //Increment duty cycle
PWM_duty_cycle=PWM_duty_cycle + PWM_open_incr;
OCR1BL = (unsigned char)(PWM_duty_cycle);//Set PWM duty cycle CH B
}
//Gate continues to open at specified upper speed (PA3)
:
:
:
//*************************************************************************