| 0,0 → 1,92 |
|---|
| #include <inttypes.h> |
| #include <avr/io.h> |
| #include <avr/interrupt.h> |
| |
| #include "main.h" |
| |
| volatile uint16_t CountMilliseconds = 0; |
| |
| |
| |
| /*****************************************************/ |
| /* Initialize Timer 0 */ |
| /*****************************************************/ |
| // timer 0 is used for the PWM generation to control the offset voltage at the air pressure sensor |
| // Its overflow interrupt routine is used to generate the beep signal and the flight control motor update rate |
| void TIMER0_Init(void) |
| { |
| uint8_t sreg = SREG; |
| |
| // disable all interrupts before reconfiguration |
| cli(); |
| |
| // Timer/Counter 0 Control Register A |
| |
| // Waveform Generation Mode is Fast PWM (Bits WGM02 = 0, WGM01 = 1, WGM00 = 1) |
| // Clear OC0A on Compare Match, set OC0A at BOTTOM, noninverting PWM (Bits COM0A1 = 1, COM0A0 = 0) |
| // Clear OC0B on Compare Match, set OC0B at BOTTOM, (Bits COM0B1 = 1, COM0B0 = 0) |
| TCCR0A &= ~((1<<COM0A0)|(1<<COM0B0)); |
| TCCR0A |= (1<<COM0A1)|(1<<COM0B1)|(1<<WGM01)|(1<<WGM00); |
| |
| // Timer/Counter 0 Control Register B |
| |
| // set clock devider for timer 0 to SYSKLOCK/8 = 20MHz / 8 = 2.5MHz |
| // i.e. the timer increments from 0x00 to 0xFF with an update rate of 2.5 MHz |
| // hence the timer overflow interrupt frequency is 2.5 MHz / 256 = 9.765 kHz |
| |
| // divider 8 (Bits CS02 = 0, CS01 = 1, CS00 = 0) |
| TCCR0B &= ~((1<<FOC0A)|(1<<FOC0B)|(1<<WGM02)); |
| TCCR0B = (TCCR0B & 0xF8)|(0<<CS02)|(1<<CS01)|(0<<CS00); |
| |
| // initialize the Output Compare Register A & B used for PWM generation on port PB3 & PB4 |
| OCR0A = 0; // for PB3 |
| OCR0B = 120; // for PB4 |
| |
| // init Timer/Counter 0 Register |
| TCNT0 = 0; |
| |
| // Timer/Counter 0 Interrupt Mask Register |
| // enable timer overflow interrupt only |
| TIMSK0 &= ~((1<<OCIE0B)|(1<<OCIE0A)); |
| TIMSK0 |= (1<<TOIE0); |
| |
| SREG = sreg; |
| } |
| |
| |
| |
| /*****************************************************/ |
| /* Interrupt Routine of Timer 0 */ |
| /*****************************************************/ |
| ISR(TIMER0_OVF_vect) // 9.765 kHz |
| { |
| static uint8_t cnt = 0; |
| |
| if(!cnt--) // every 10th run (9.765kHz/10 = 976Hz) |
| { |
| cnt = 9; |
| CountMilliseconds++; // increment millisecond counter |
| } |
| } |
| |
| |
| // ----------------------------------------------------------------------- |
| uint16_t SetDelay (uint16_t t) |
| { |
| return(CountMilliseconds + t - 1); |
| } |
| |
| // ----------------------------------------------------------------------- |
| int8_t CheckDelay(uint16_t t) |
| { |
| return(((t - CountMilliseconds) & 0x8000) >> 8); // check sign bit |
| } |
| |
| // ----------------------------------------------------------------------- |
| void Delay_ms(uint16_t w) |
| { |
| unsigned int t_stop; |
| t_stop = SetDelay(w); |
| while (!CheckDelay(t_stop)); |
| } |
| |