Added timeout (in microseconds) parameter to pulseIn(). Defaults to 1000000 (1 second).
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@ -10,6 +10,8 @@
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#ifdef __cplusplus
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#include "HardwareSerial.h"
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unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout = 1000000L);
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// WMath prototypes
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long random(long);
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long random(long, long);
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@ -87,6 +87,7 @@ extern "C"{
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#define clockCyclesPerMicrosecond() ( F_CPU / 1000000L )
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#define clockCyclesToMicroseconds(a) ( (a) / clockCyclesPerMicrosecond() )
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#define microsecondsToClockCycles(a) ( (a) * clockCyclesPerMicrosecond() )
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typedef uint8_t boolean;
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typedef uint8_t byte;
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@ -118,7 +119,7 @@ void printIntegerInBase(unsigned long n, unsigned long base);
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unsigned long millis(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);
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unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout);
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void shiftOut(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, byte val);
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@ -26,10 +26,10 @@
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#include "pins_arduino.h"
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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 10 microseconds
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* to 3 minutes in length, but must be called at least N microseconds before
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* the start of the pulse. */
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unsigned long pulseIn(uint8_t pin, uint8_t state)
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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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unsigned long pulseIn(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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@ -39,17 +39,23 @@ unsigned long pulseIn(uint8_t pin, uint8_t state)
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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) / 16;
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// wait for the pulse to start
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while ((*portInputRegister(port) & bit) != stateMask)
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;
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if (numloops++ == maxloops)
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return 0;
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// wait for the pulse to stop
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while ((*portInputRegister(port) & bit) == stateMask)
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width++;
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// convert the reading to microseconds. The loop has been determined
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// to be 10 clock cycles long and have about 12 clocks between the edge
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// to be 10 clock cycles long and have about 16 clocks between the edge
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// and the start of the loop. There will be some error introduced by
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// the interrupt handlers.
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return clockCyclesToMicroseconds(width * 10 + 12);
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return clockCyclesToMicroseconds(width * 10 + 16);
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}
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