Function sendMark

src/TinyIRSender.hpp:71–104

* Generate 38 kHz IR signal by bit banging and using delayMicroseconds() and micros() */

 * Generate 38 kHz IR signal by bit banging and using delayMicroseconds() and micros()
 */
void sendMark(uint8_t aSendPin, unsigned int aMarkMicros) {
    unsigned long tMicros = micros();
    unsigned long tNextPeriodEnding = tMicros;
#if defined(F_CPU)
    unsigned long tEndMicros = tMicros + (112 / (F_CPU / MICROS_IN_ONE_SECOND)) + aMarkMicros; // To compensate for call duration - 112 is an empirical value
#else
    unsigned long tEndMicros = tMicros + aMarkMicros;
#endif
    do {
        /*
         * Generate pulse
         */
        noInterrupts(); // do not let interrupts extend the short on period
        digitalWriteFast(aSendPin, HIGH);
        delayMicroseconds(8); // 8 us for a 30 % duty cycle for 38 kHz
        digitalWriteFast(aSendPin, LOW);
        interrupts(); // Enable interrupts - to keep micros correct- for the longer off period 3.4 us until receive ISR is active (for 7 us + pop's)

        /*
         * PWM pause timing and end check
         * Minimal pause duration is 4.3 us
         */
        tNextPeriodEnding += 26; // 26.3 us period for 38 kHz; 26 us -> 38.48 kHz
        do {
            tMicros = micros(); // we have only 4 us resolution for AVR @16MHz
            /*
             * Exit the forever loop if aMarkMicros has reached
             */
            if (tMicros >= tEndMicros) {
                return;
            }
        } while (tMicros < tNextPeriodEnding);
    } while (true);
}

/*
 * Send NEC with 16 bit address and command, even if aCommand < 0x100 (I.E. ONKYO)