--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/sanguino/cores/arduino/wiring_pulse.c Thu Jul 07 12:23:34 2016 +0200
@@ -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);
+}