From 5f3976696ddf5d02ea7e6f805ce655e1f281e6ed Mon Sep 17 00:00:00 2001 From: "David A. Mellis" Date: Sat, 6 Oct 2007 14:47:50 +0000 Subject: Moving hardware/targets to hardware/cores. --- cores/arduino/wiring_pulse.c | 55 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100755 cores/arduino/wiring_pulse.c (limited to 'cores/arduino/wiring_pulse.c') diff --git a/cores/arduino/wiring_pulse.c b/cores/arduino/wiring_pulse.c new file mode 100755 index 0000000..642a5a2 --- /dev/null +++ b/cores/arduino/wiring_pulse.c @@ -0,0 +1,55 @@ +/* + 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 10 microseconds + * to 3 minutes in length, but must be called at least N microseconds before + * the start of the pulse. */ +unsigned long pulseIn(uint8_t pin, uint8_t state) +{ + // 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 + + // wait for the pulse to start + while ((*portInputRegister(port) & bit) != stateMask) + ; + + // wait for the pulse to stop + while ((*portInputRegister(port) & bit) == stateMask) + width++; + + // convert the reading to microseconds. The loop has been determined + // to be 10 clock cycles long and have about 12 clocks between the edge + // and the start of the loop. There will be some error introduced by + // the interrupt handlers. + return clockCyclesToMicroseconds(width * 10 + 12); +} -- cgit v1.2.3-18-g5258