diff options
| -rw-r--r-- | cores/arduino/Arduino.h | 2 | ||||
| -rw-r--r-- | cores/arduino/wiring_pulse.c | 44 |
2 files changed, 45 insertions, 1 deletions
diff --git a/cores/arduino/Arduino.h b/cores/arduino/Arduino.h index 07bccd8..f1da68d 100644 --- a/cores/arduino/Arduino.h +++ b/cores/arduino/Arduino.h @@ -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); diff --git a/cores/arduino/wiring_pulse.c b/cores/arduino/wiring_pulse.c index 2ac6988..49fa38d 100644 --- a/cores/arduino/wiring_pulse.c +++ b/cores/arduino/wiring_pulse.c @@ -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); -}
\ No newline at end of file +} + +/* 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; +} |