diff options
author | HampusM <hampus@hampusmat.com> | 2022-03-07 13:48:57 +0100 |
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committer | HampusM <hampus@hampusmat.com> | 2022-03-07 13:48:57 +0100 |
commit | 563f69b870a7f71026c50605b531ed40d667b0a2 (patch) | |
tree | f9dd8374cae6affb3b52d79e22823c78187b99ed /cores/xinput/wiring_pulse.c | |
parent | f4a2dc0440d17e4c9e609e01e12fcd786d268cf7 (diff) |
Diffstat (limited to 'cores/xinput/wiring_pulse.c')
-rw-r--r-- | cores/xinput/wiring_pulse.c | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/cores/xinput/wiring_pulse.c b/cores/xinput/wiring_pulse.c new file mode 100644 index 0000000..d6e0434 --- /dev/null +++ b/cores/xinput/wiring_pulse.c @@ -0,0 +1,93 @@ +/* + wiring_pulse.c - pulseIn() function + Part of Arduino - http://www.arduino.cc/ + + Copyright (c) 2005-2006 David A. Mellis + + This library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + This library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General + Public License along with this library; if not, write to the + Free Software Foundation, Inc., 59 Temple Place, Suite 330, + Boston, MA 02111-1307 USA +*/ + +#include "wiring_private.h" +#include "pins_arduino.h" + +/* 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. + * + * This function performs better with short pulses in noInterrupt() context + */ +unsigned long pulseIn(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); + + // convert the timeout from microseconds to a number of times through + // the initial loop; it takes approximately 16 clock cycles per iteration + unsigned long maxloops = microsecondsToClockCycles(timeout)/16; + + unsigned long width = countPulseASM(portInputRegister(port), bit, stateMask, maxloops); + + // prevent clockCyclesToMicroseconds to return bogus values if countPulseASM timed out + if (width) + return clockCyclesToMicroseconds(width * 16 + 16); + else + return 0; +} + +/* 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 startMicros = micros(); + + // wait for any previous pulse to end + while ((*portInputRegister(port) & bit) == stateMask) { + if (micros() - startMicros > timeout) + return 0; + } + + // wait for the pulse to start + while ((*portInputRegister(port) & bit) != stateMask) { + if (micros() - startMicros > timeout) + return 0; + } + + unsigned long start = micros(); + // wait for the pulse to stop + while ((*portInputRegister(port) & bit) == stateMask) { + if (micros() - startMicros > timeout) + return 0; + } + return micros() - start; +} |