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pulseIn: add alternative implementation based on micros()

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pulseInLong is suitable for long pulses in interrupt context
This commit is contained in:
Martino Facchin 2015-03-02 13:35:30 +01:00
parent 93f74f84ce
commit d4a80be045
2 changed files with 45 additions and 1 deletions
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2
hardware/arduino/avr/cores/arduino/Arduino.h
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@ -134,6 +134,7 @@ unsigned long micros(void);
void delay(unsigned long);
void delayMicroseconds(unsigned int us);
unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout);
unsigned long pulseInLong(uint8_t pin, uint8_t state, unsigned long timeout);
void shiftOut(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, uint8_t val);
uint8_t shiftIn(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder);
@ -232,6 +233,7 @@ uint16_t makeWord(byte h, byte l);
#define word(...) makeWord(__VA_ARGS__)
unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout = 1000000L);
unsigned long pulseInLong(uint8_t pin, uint8_t state, unsigned long timeout = 1000000L);
void tone(uint8_t _pin, unsigned int frequency, unsigned long duration = 0);
void noTone(uint8_t _pin);

44
hardware/arduino/avr/cores/arduino/wiring_pulse.c
View File

@ -49,4 +49,46 @@ unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout)
width = countPulseASM(portInputRegister(port), bit, stateMask, maxloops);
return clockCyclesToMicroseconds(width * 16 + 16);
}
}
/* Measures the length (in microseconds) of a pulse on the pin; state is HIGH
* or LOW, the type of pulse to measure. Works on pulses from 2-3 microseconds
* to 3 minutes in length, but must be called at least a few dozen microseconds
* before the start of the pulse.
*
* ATTENTION:
* this function relies on micros() so cannot be used in noInterrupt() context
*/
unsigned long pulseInLong(uint8_t pin, uint8_t state, unsigned long timeout)
{
// cache the port and bit of the pin in order to speed up the
// pulse width measuring loop and achieve finer resolution. calling
// digitalRead() instead yields much coarser resolution.
uint8_t bit = digitalPinToBitMask(pin);
uint8_t port = digitalPinToPort(pin);
uint8_t stateMask = (state ? bit : 0);
unsigned long width = 0; // keep initialization out of time critical area
// convert the timeout from microseconds to a number of times through
// the initial loop; it takes 16 clock cycles per iteration.
unsigned long numloops = 0;
unsigned long maxloops = microsecondsToClockCycles(timeout);
// wait for any previous pulse to end
while ((*portInputRegister(port) & bit) == stateMask)
if (numloops++ == maxloops)
return 0;
// wait for the pulse to start
while ((*portInputRegister(port) & bit) != stateMask)
if (numloops++ == maxloops)
return 0;
unsigned long start = micros();
// wait for the pulse to stop
while ((*portInputRegister(port) & bit) == stateMask) {
if (numloops++ == maxloops)
return 0;
}
return micros() - start;
}