128 lines
5.1 KiB
C
128 lines
5.1 KiB
C
#include "header.h"
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// 14.3.1 : alternate functions for led2 PB1
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// - OC1A (Timer/Counter1 Output Compare Match A Output)
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// - 16.11.1 controlled by COM1A1:0 in TCCR1A
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// - Table 16-2 : Compare Output Mode, Fast PWM
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// (1 << COM1A1) | (0 << COM1A0) -> non-inverting mode
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// - Table 16-4 : set timer 1 in fast PWM mode, with top as ICR1 or OCR1A
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// - ICR1 : Input Capture Register ((1 << WGM13) | (1 << WGM12) | (1 << WGM11) | (0 << WGM10))
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// - OCR1A : Output Compare Register ((1 << WGM13) | (1 << WGM12) | (1 << WGM11) | (1 << WGM10))
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// -> if OCR1A is top, it's also duty cycle, so changing duty cycle will also change frequency
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// -> if ICR1 is top, OCR1A is duty cycle, so it can be changed independantly
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// - PCINT1 (Pin Change Interrupt 1) : to interrupt when pin change, in input mode only
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// calulations
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// - frequency is 16Mhz -> it means that the clock runs 16 000 000 times per seconds
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// - and the timer1 can store 16 bits value of cycle -> which is 2^16 = 65536
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// - so it will only last 65536/16000000 = 0,004096 second
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// - if i want my cycle to be 0.001 second, prescaler 1 is enough
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// - if i want my cycle to be 0.01 second, which prescaler ?
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// - 8 * 0,004096 = 0.032768 -> it is enough
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// - 64 * 0,004096 = 0.262144 -> it is largely enough
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// - after how many "ticks" do i need to reset my clock, for a duration of 0.01s, for every prescalers :
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// - 1 : (16000000 / 1) * 0.01 = 16000000 * 0.01 = 160000 "ticks"
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// - 8 : (16000000 / 8) * 0.01 = 2000000 * 0.01 = 20000 "ticks"
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// - 64 : (16000000 / 64) * 0.01 = 250000 * 0.01 = 2500 "ticks"
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// - 256 : (16000000 / 256) * 0.01 = 62500 * 0.01 = 625 "ticks"
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// - 1024 : (16000000 / 1024) * 0.01 = 15625 * 0.01 = 156,25 "ticks"
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// alternatively, can use the default values :
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// - Fast PWM, 8-bit, TOP 0x00FF (255)
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// - Fast PWM, 9-bit, TOP 0x01FF (511)
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// - Fast PWM, 10-bit, TOP 0x03FF (1023)
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// no need to set a second for the "blinking" with PWM and duty cycle :
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// only need to use a top value convenient, like a multiple of 100
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// if choose top value of 100 :
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// - at prescaler 1 : 100 / 16000000 = 0.00000625s (it takes this time to do a cycle)
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// - at prescaler 8 : (100 * 8) / 16000000 = 0.00005s
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// - at prescaler 64 : (100 * 64) / 16000000 = 0.0004s
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// - at prescaler 256 : (100 * 256) / 16000000 = 0.0016s
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// - at prescaler 1024 : (100 * 1024) / 16000000 = 0.0064s
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// if choose top value of 1000 :
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// - at prescaler 1 : 1000 / 16000000 = 0.0000625s (it takes this time to do a cycle)
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// - at prescaler 8 : (1000 * 8) / 16000000 = 0.0005s
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// - at prescaler 64 : (1000 * 64) / 16000000 = 0.004s
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// - at prescaler 256 : (1000 * 256) / 16000000 = 0.016s
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// - at prescaler 1024 : (1000 * 1024) / 16000000 = 0.064s
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// 16.9.3 : timer1 fast PWM
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// TIMER 1
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#define T1_PWM_PRESCALER 256 // can be 1, 8, 64, 256, 1024
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#define T1_DUTY_CYCLE_PERCENT 9
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// #define FREQUENCY_MS 1
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#define T1_TOP_VALUE 1000
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// TIMER 0
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#define T0_PWM_PRESCALER 256 // can be 1, 8, 64, 256, 1024
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#define T0_FREQUENCY_MS 20
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typedef enum {
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DOWN,
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UP
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} Slope;
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volatile uint8_t duty_cycle = T1_DUTY_CYCLE_PERCENT;
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volatile Slope slope = UP;
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void blink_led_1() {
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TCCR1A = (1 << WGM11); // Table 16-4 : set timer1 in fast PWM mode 14, with TOP ICR1, so we can use OCR1A for duty cycle and keep ICR1 for frequency
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TCCR1B = (1 << WGM13) | (1 << WGM12); // mode 15 with OCR1A TOP prevent using duty cycle trigger on OC1A (OCR1B is free but triggers OC1B -> PB2)
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// other fast PWM modes 5, 6, and 7 uses predefined TOP, preventing to define a multiple of 100 for percent accuracy
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TCCR1A |= (1 << COM1A1); // Table 16-2 : set non-inverting mode to trigger OC1A on fast PWM (14.3.1 : OC1A is alternate function of PB1)
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TCCR1B |= T1_PRESCALE_SET(T1_PWM_PRESCALER); // Table 16-5 : set the appropriate prescale values for timer 1
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// ICR1 = TIME_MS(FREQUENCY_MS, T1_PWM_PRESCALER); // top value for Xms
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ICR1 = T1_TOP_VALUE;
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OCR1A = PERCENT(duty_cycle, ICR1); // 16.9.3 : duty cycle
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}
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void vary_duty() {
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TCCR0A = (1 << WGM11); // Table 15-8 : set timer0 in CTC mode, with TOP OCRA (15.9.1 : WGM11 in register TCCR0A)
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OCR0A = TIME_MS(T0_FREQUENCY_MS, T0_PWM_PRESCALER); // 15.9.4 : compare value to trigger an Output Compare interrupt on register A
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TCCR0B |= T0_PRESCALE_SET(T0_PWM_PRESCALER); // 15.9.2 : set the appropriate prescale values for timer 0
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TIMSK0 = (1 << OCIE0A); // 15.9.6 : set OCIE0A in TIMSK0 to enable Compare Match A interrupt in Timer0
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}
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// use timers interruptions to varie led1 intensity using duty cycle, from 0% to 100% to 0% in 1 second
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// timer1 sets the led duty cycle, timer0 change the duty cycle percentage
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int main() {
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MODE_OUTPUT(LED1);
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CLEAR_ELEM(LED1);
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MODE_OUTPUT(LED2);
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CLEAR_ELEM(LED2);
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MODE_OUTPUT(LED3);
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CLEAR_ELEM(LED3);
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MODE_OUTPUT(LED4);
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CLEAR_ELEM(LED4);
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SREG |= ENABLE_GLOBAL_INTERRUPT;
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blink_led_1();
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vary_duty();
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while (1);
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}
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ISR(TIMER0_COMPA_vect) {
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if (slope == UP) {
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if (duty_cycle >= 100) {
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slope = DOWN;
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} else {
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duty_cycle += 2;
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}
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}
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if (slope == DOWN) {
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if (duty_cycle <= 0) {
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slope = UP;
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} else {
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duty_cycle -= 2;
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}
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}
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} |