1 files changed, 53 insertions, 0 deletions
diff --git a/arduino/cores/nRF5/pulse.c b/arduino/cores/nRF5/pulse.c
new file mode 100755
index 0000000..9dff9f5
--- /dev/null
+++ b/arduino/cores/nRF5/pulse.c
@@ -0,0 +1,53 @@
+/*
+  Copyright (c) 2015 Arduino LLC.  All right reserved.
+
+  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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#include "nrf.h"
+
+#include <Arduino.h>
+
+// See pulse_asm.S
+extern unsigned long countPulseASM(const volatile uint32_t *port, uint32_t bit, uint32_t stateMask, unsigned long maxloops);
+
+/* 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. */
+uint32_t pulseIn(uint32_t pin, uint32_t state, uint32_t 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.
+  // PinDescription p = g_APinDescription[pin];
+  uint32_t bit = digitalPinToBitMask(pin); //p.ulPin;
+  uint32_t stateMask = state ? bit : 0;
+
+  // convert the timeout from microseconds to a number of times through
+  // the initial loop; it takes (roughly) 13 clock cycles per iteration.
+  uint32_t maxloops = microsecondsToClockCycles(timeout) / 13;
+
+  uint32_t width = countPulseASM(portInputRegister(digitalPinToPort(pin)), bit, stateMask, maxloops);
+
+  // convert the reading to microseconds. The loop has been determined
+  // to be 13 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.
+  if (width)
+    return clockCyclesToMicroseconds(width * 13 + 16);
+  else
+    return 0;
+}