diff options
author | Nick Brassel <nick@tzarc.org> | 2021-08-29 08:20:25 +1000 |
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committer | Nick Brassel <nick@tzarc.org> | 2021-08-29 08:20:25 +1000 |
commit | f061ca497464fe85284906fb163a33eaee7a91ef (patch) | |
tree | 33ef1bfb529aed382e8526c607c4e18717f92571 /lib/usbhost/arduino-1.0.1/cores/arduino/wiring_pulse.c | |
parent | ff65185dec6f97be1eb49f17cea526a0d0bbf3d6 (diff) | |
parent | 4bad375d7c09d949a9dcdd4feba147c9c7a67ec6 (diff) |
Breaking changes develop merge to master, 2021Q3 edition. (#14196)
Diffstat (limited to 'lib/usbhost/arduino-1.0.1/cores/arduino/wiring_pulse.c')
-rw-r--r-- | lib/usbhost/arduino-1.0.1/cores/arduino/wiring_pulse.c | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/lib/usbhost/arduino-1.0.1/cores/arduino/wiring_pulse.c b/lib/usbhost/arduino-1.0.1/cores/arduino/wiring_pulse.c new file mode 100644 index 0000000000..0d968865d2 --- /dev/null +++ b/lib/usbhost/arduino-1.0.1/cores/arduino/wiring_pulse.c @@ -0,0 +1,69 @@ +/* + 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 + + $Id: wiring.c 248 2007-02-03 15:36:30Z mellis $ +*/ + +#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. */ +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); + 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) / 16; + + // 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; + + // wait for the pulse to stop + while ((*portInputRegister(port) & bit) == stateMask) { + if (numloops++ == maxloops) + return 0; + width++; + } + + // convert the reading to microseconds. The loop has been determined + // to be 20 clock cycles long and have about 16 clocks between the edge + // and the start of the loop. There will be some error introduced by + // the interrupt handlers. + return clockCyclesToMicroseconds(width * 21 + 16); +} |