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pulseIn: add alternative implementation based on micros()
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@ -22,7 +22,11 @@
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/* Measures the length (in microseconds) of a pulse on the pin; state is HIGH
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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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* 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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* 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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* before the start of the pulse.
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*
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* ATTENTION:
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* This function performs better with short pulses in noInterrupt() context
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*/
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uint32_t pulseIn( uint32_t pin, uint32_t state, uint32_t timeout )
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uint32_t pulseIn( uint32_t pin, uint32_t state, uint32_t timeout )
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{
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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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// cache the port and bit of the pin in order to speed up the
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@ -47,3 +51,43 @@ uint32_t pulseIn( uint32_t pin, uint32_t state, uint32_t timeout )
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else
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else
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return 0;
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return 0;
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}
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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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uint32_t 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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PinDescription p = g_APinDescription[pin];
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uint32_t bit = p.ulPin;
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uint32_t stateMask = state ? bit : 0;
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// convert the timeout from microseconds to a number of times through
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// the initial loop; it takes 18 clock cycles per iteration.
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unsigned long maxloops = microsecondsToClockCycles(timeout) / 10;
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// wait for any previous pulse to end
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while ((p.pPort->PIO_PDSR & bit) == stateMask)
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if (--maxloops == 0)
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return 0;
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// wait for the pulse to start
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while ((p.pPort->PIO_PDSR & bit) != stateMask)
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if (--maxloops == 0)
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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 ((p.pPort->PIO_PDSR & bit) == stateMask) {
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if (--maxloops == 0)
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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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@ -31,7 +31,7 @@ unsigned long countPulseASM(const volatile uint32_t *port, uint32_t bit, uint32_
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* before the start of the pulse.
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* before the start of the pulse.
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*/
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*/
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extern uint32_t pulseIn( uint32_t ulPin, uint32_t ulState, uint32_t ulTimeout = 1000000L ) ;
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extern uint32_t pulseIn( uint32_t ulPin, uint32_t ulState, uint32_t ulTimeout = 1000000L ) ;
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extern uint32_t pulseInLong( uint8_t pin, uint8_t state, unsigned long timeout = 1000000L ) ;
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#ifdef __cplusplus
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#ifdef __cplusplus
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}
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}
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