pulseIn: add alternative implementation based on micros()
pulseInLong is suitable for long pulses in interrupt context
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@ -134,6 +134,7 @@ unsigned long micros(void);
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void delay(unsigned long);
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void delayMicroseconds(unsigned int us);
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unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout);
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unsigned long pulseInLong(uint8_t pin, uint8_t state, unsigned long timeout);
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void shiftOut(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, uint8_t val);
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uint8_t shiftIn(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder);
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@ -232,6 +233,7 @@ uint16_t makeWord(byte h, byte l);
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#define word(...) makeWord(__VA_ARGS__)
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unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout = 1000000L);
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unsigned long pulseInLong(uint8_t pin, uint8_t state, unsigned long timeout = 1000000L);
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void tone(uint8_t _pin, unsigned int frequency, unsigned long duration = 0);
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void noTone(uint8_t _pin);
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@ -50,3 +50,45 @@ unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout)
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width = countPulseASM(portInputRegister(port), bit, stateMask, maxloops);
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return clockCyclesToMicroseconds(width * 16 + 16);
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}
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/* Measures the length (in microseconds) of a pulse on the pin; state is HIGH
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* or LOW, the type of pulse to measure. Works on pulses from 2-3 microseconds
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* to 3 minutes in length, but must be called at least a few dozen microseconds
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* before the start of the pulse.
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*
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* ATTENTION:
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* this function relies on micros() so cannot be used in noInterrupt() context
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*/
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unsigned long pulseInLong(uint8_t pin, uint8_t state, unsigned long timeout)
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{
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// cache the port and bit of the pin in order to speed up the
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// pulse width measuring loop and achieve finer resolution. calling
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// digitalRead() instead yields much coarser resolution.
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uint8_t bit = digitalPinToBitMask(pin);
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uint8_t port = digitalPinToPort(pin);
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uint8_t stateMask = (state ? bit : 0);
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unsigned long width = 0; // keep initialization out of time critical area
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// convert the timeout from microseconds to a number of times through
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// the initial loop; it takes 16 clock cycles per iteration.
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unsigned long numloops = 0;
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unsigned long maxloops = microsecondsToClockCycles(timeout);
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// wait for any previous pulse to end
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while ((*portInputRegister(port) & bit) == stateMask)
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if (numloops++ == maxloops)
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return 0;
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// wait for the pulse to start
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while ((*portInputRegister(port) & bit) != stateMask)
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if (numloops++ == maxloops)
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return 0;
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unsigned long start = micros();
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// wait for the pulse to stop
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while ((*portInputRegister(port) & bit) == stateMask) {
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if (numloops++ == maxloops)
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return 0;
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}
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return micros() - start;
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}
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