40 lines
955 B
C++
40 lines
955 B
C++
#include "pwm.h"
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const uint16_t PWM::PRESCALERS[] = {0, 1, 8, 64, 256, 1024};
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const uint8_t PWM::PRESCALER_COUNT = sizeof(PRESCALERS) / sizeof(uint16_t);
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void PWM::init() const volatile
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{
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// fast pwm mode, top = OCR0A, non inverting mode
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TCCR0A = _BV(WGM00) | _BV(WGM01);
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TCCR0B = _BV(WGM02);
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// output signal on PB4
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DDRB |= _BV(PB4);
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}
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void PWM::setFrequency(uint32_t freq) const volatile
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{
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uint16_t p_ideal = ceil(float(F_CPU) / (freq * 0x100));
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for(int8_t i = PRESCALER_COUNT - 1; i >= 0 && PRESCALERS[i] >= p_ideal; i--)
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TCCR0B = (TCCR0B & 0xF8) | i; // set prescaler
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if(p_ideal)
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OCR0A = (uint8_t) (float(F_CPU) / (freq * PRESCALERS[TCCR0B & 0x07]));
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}
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void PWM::setValue(uint8_t value) const volatile
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{
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if(value)
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{
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OCR0B = value;
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TCCR0A |= _BV(COM0B1);
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} else
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{
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TCCR0A &= ~_BV(COM0B1);
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}
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}
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uint8_t PWM::getTop() const volatile
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{
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return OCR0A;
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}
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