diff --git a/cores/arduino/Arduino.h b/cores/arduino/Arduino.h
index fa362d288e75b2ffb2005694c71fe2f1676609e9..844789674e391581ffdabdf899e7911f857ee3f1 100644
--- a/cores/arduino/Arduino.h
+++ b/cores/arduino/Arduino.h
@@ -71,7 +71,7 @@ void loop( void ) ;
#include "Tone.h"
#include "WMath.h"
#include "HardwareSerial.h"
-// #include "wiring_pulse.h"
+ #include "pulse.h"
#include "delay.h"
#include "Uart.h"
#endif // __cplusplus
diff --git a/cores/arduino/pulse.c b/cores/arduino/pulse.c
new file mode 100644
index 0000000000000000000000000000000000000000..2dd03bf476f8c6dd2596859b8b1eb14fa96b5f0b
--- /dev/null
+++ b/cores/arduino/pulse.c
@@ -0,0 +1,52 @@
+/*
+ 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 <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 = 1 << 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(&(PORT->Group[p.ulPort].IN.reg), 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;
+}
+
diff --git a/cores/arduino/pulse.h b/cores/arduino/pulse.h
new file mode 100644
index 0000000000000000000000000000000000000000..9c620f12adb0dfe1acaa059d4d9b63fa936f6872
--- /dev/null
+++ b/cores/arduino/pulse.h
@@ -0,0 +1,39 @@
+/*
+ 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
+*/
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * \brief 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);
+
+#ifdef __cplusplus
+// Provides a version of pulseIn with a default argument (C++ only)
+uint32_t pulseIn(uint32_t pin, uint32_t state, uint32_t timeout = 1000000L);
+
+} // extern "C"
+#endif
+
diff --git a/cores/arduino/pulse_asm.S b/cores/arduino/pulse_asm.S
new file mode 100644
index 0000000000000000000000000000000000000000..7b94f158bfce52b76d3901d1bfd4eefa2b2016d8
--- /dev/null
+++ b/cores/arduino/pulse_asm.S
@@ -0,0 +1,175 @@
+/*
+ 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
+*/
+
+/*
+
+The following function has been compiled to ASM with gcc
+
+ unsigned long countPulseASM(const volatile uint32_t *port, uint32_t bit, uint32_t stateMask, unsigned long maxloops)
+ {
+ unsigned long width = 0;
+
+ // wait for any previous pulse to end
+ while ((*port & bit) == stateMask)
+ if (--maxloops == 0)
+ return 0;
+
+ // wait for the pulse to start
+ while ((*port & bit) != stateMask)
+ if (--maxloops == 0)
+ return 0;
+
+ // wait for the pulse to stop
+ while ((*port & bit) == stateMask) {
+ if (++width == maxloops)
+ return 0;
+ }
+ return width;
+ }
+
+using the command line:
+
+ arm-none-eabi-gcc -mcpu=cortex-m0plus -mthumb -c -Os -W -ffunction-sections -fdata-sections \
+ -nostdlib --param max-inline-insns-single=500 -fno-exceptions -MMD \
+ -DF_CPU=48000000L -DARDUINO=10602 -DARDUINO_SAMD_ZERO -DARDUINO_ARCH_SAMD \
+ -D__SAMD21G18A__ -DUSB_VID=0x2341 -DUSB_PID=0x004d -DUSBCON \
+ -DUSB_MANUFACTURER="Arduino LLC" -DUSB_PRODUCT="Arduino Zero" \
+ -I/Code/arduino/build/linux/work/hardware/tools/CMSIS/CMSIS/Include/ \
+ -I/Code/arduino/build/linux/work/hardware/tools/CMSIS/Device/ATMEL/ \
+ -I/Code/arduino/build/linux/work/hardware/arduino/samd/cores/arduino \
+ -I/Code/arduino/build/linux/work/hardware/arduino/samd/variants/arduino_zero \
+ count.c -Wa,-ahlmsd=output.lst -dp -fverbose-asm -S
+
+The result has been slightly edited to increase readability.
+
+*/
+
+ .cpu cortex-m0plus
+ .fpu softvfp
+ .eabi_attribute 20, 1 @ Tag_ABI_FP_denormal
+ .eabi_attribute 21, 1 @ Tag_ABI_FP_exceptions
+ .eabi_attribute 23, 3 @ Tag_ABI_FP_number_model
+ .eabi_attribute 24, 1 @ Tag_ABI_align8_needed
+ .eabi_attribute 25, 1 @ Tag_ABI_align8_preserved
+ .eabi_attribute 26, 1 @ Tag_ABI_enum_size
+ .eabi_attribute 30, 4 @ Tag_ABI_optimization_goals
+ .eabi_attribute 34, 0 @ Tag_CPU_unaligned_access
+ .eabi_attribute 18, 4 @ Tag_ABI_PCS_wchar_t
+ .file "count.c"
+@ GNU C (GNU Tools for ARM Embedded Processors (Arduino build)) version 4.8.3 20140228 (release) [ARM/embedded-4_8-branch revision 208322] (arm-none-eabi)
+@ compiled by GNU C version 4.3.2, GMP version 4.3.2, MPFR version 2.4.2, MPC version 0.8.1
+@ GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
+@ options passed:
+@ -I /Code/arduino/build/linux/work/hardware/tools/CMSIS/CMSIS/Include/
+@ -I /Code/arduino/build/linux/work/hardware/tools/CMSIS/Device/ATMEL/
+@ -I /Code/arduino/build/linux/work/hardware/arduino/samd/cores/arduino
+@ -I /Code/arduino/build/linux/work/hardware/arduino/samd/variants/arduino_zero
+@ -imultilib armv6-m
+@ -iprefix /Code/arduino/build/linux/work/hardware/tools/gcc-arm-none-eabi-4.8.3-2014q1/bin/../lib/gcc/arm-none-eabi/4.8.3/
+@ -isysroot /Code/arduino/build/linux/work/hardware/tools/gcc-arm-none-eabi-4.8.3-2014q1/bin/../arm-none-eabi
+@ -MMD count.d -D__USES_INITFINI__ -D F_CPU=48000000L -D ARDUINO=10602
+@ -D ARDUINO_SAMD_ZERO -D ARDUINO_ARCH_SAMD -D __SAMD21G18A__
+@ -D USB_VID=0x2341 -D USB_PID=0x004d -D USBCON
+@ -D USB_MANUFACTURER=Arduino LLC -D USB_PRODUCT=Arduino Zero count.c
+@ -mcpu=cortex-m0plus -mthumb -Os -Wextra -ffunction-sections
+@ -fdata-sections -fno-exceptions -fverbose-asm
+@ --param max-inline-insns-single=500
+@ options enabled: -faggressive-loop-optimizations -fauto-inc-dec
+@ -fbranch-count-reg -fcaller-saves -fcombine-stack-adjustments -fcommon
+@ -fcompare-elim -fcprop-registers -fcrossjumping -fcse-follow-jumps
+@ -fdata-sections -fdefer-pop -fdelete-null-pointer-checks -fdevirtualize
+@ -fdwarf2-cfi-asm -fearly-inlining -feliminate-unused-debug-types
+@ -fexpensive-optimizations -fforward-propagate -ffunction-cse
+@ -ffunction-sections -fgcse -fgcse-lm -fgnu-runtime
+@ -fguess-branch-probability -fhoist-adjacent-loads -fident -fif-conversion
+@ -fif-conversion2 -findirect-inlining -finline -finline-atomics
+@ -finline-functions -finline-functions-called-once
+@ -finline-small-functions -fipa-cp -fipa-profile -fipa-pure-const
+@ -fipa-reference -fipa-sra -fira-hoist-pressure -fira-share-save-slots
+@ -fira-share-spill-slots -fivopts -fkeep-static-consts
+@ -fleading-underscore -fmath-errno -fmerge-constants -fmerge-debug-strings
+@ -fomit-frame-pointer -foptimize-register-move -foptimize-sibling-calls
+@ -fpartial-inlining -fpeephole -fpeephole2 -fprefetch-loop-arrays
+@ -freg-struct-return -fregmove -freorder-blocks -freorder-functions
+@ -frerun-cse-after-loop -fsched-critical-path-heuristic
+@ -fsched-dep-count-heuristic -fsched-group-heuristic -fsched-interblock
+@ -fsched-last-insn-heuristic -fsched-pressure -fsched-rank-heuristic
+@ -fsched-spec -fsched-spec-insn-heuristic -fsched-stalled-insns-dep
+@ -fschedule-insns2 -fsection-anchors -fshow-column -fshrink-wrap
+@ -fsigned-zeros -fsplit-ivs-in-unroller -fsplit-wide-types
+@ -fstrict-aliasing -fstrict-overflow -fstrict-volatile-bitfields
+@ -fsync-libcalls -fthread-jumps -ftoplevel-reorder -ftrapping-math
+@ -ftree-bit-ccp -ftree-builtin-call-dce -ftree-ccp -ftree-ch
+@ -ftree-coalesce-vars -ftree-copy-prop -ftree-copyrename -ftree-cselim
+@ -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre
+@ -ftree-loop-if-convert -ftree-loop-im -ftree-loop-ivcanon
+@ -ftree-loop-optimize -ftree-parallelize-loops= -ftree-phiprop -ftree-pre
+@ -ftree-pta -ftree-reassoc -ftree-scev-cprop -ftree-sink
+@ -ftree-slp-vectorize -ftree-slsr -ftree-sra -ftree-switch-conversion
+@ -ftree-tail-merge -ftree-ter -ftree-vect-loop-version -ftree-vrp
+@ -funit-at-a-time -fverbose-asm -fzero-initialized-in-bss -mlittle-endian
+@ -mpic-data-is-text-relative -msched-prolog -mthumb
+@ -mvectorize-with-neon-quad
+
+ .section .text.countPulseASM,"ax",%progbits
+ .align 1
+ .global countPulseASM
+ .code 16
+ .thumb_func
+ .type countPulseASM, %function
+countPulseASM:
+ push {r4, r5, lr} @ @ 112 *push_multi [length = 2]
+.L2:
+ ldr r4, [r0] @ D.11539, *port_7(D) @ 22 *thumb1_movsi_insn/7 [length = 2]
+ and r4, r1 @ D.11539, bit @ 24 *thumb1_andsi3_insn [length = 2]
+ cmp r4, r2 @ D.11539, stateMask @ 25 cbranchsi4_insn/1 [length = 4]
+ bne .L5 @,
+ sub r3, r3, #1 @ maxloops, @ 17 *thumb1_addsi3/2 [length = 2]
+ cmp r3, #0 @ maxloops, @ 18 cbranchsi4_insn/1 [length = 4]
+ bne .L2 @,
+ b .L10 @ @ 127 *thumb_jump [length = 2]
+.L6:
+ sub r3, r3, #1 @ maxloops, @ 30 *thumb1_addsi3/2 [length = 2]
+ cmp r3, #0 @ maxloops, @ 31 cbranchsi4_insn/1 [length = 4]
+ beq .L10 @,
+.L5:
+ ldr r4, [r0] @ D.11539, *port_7(D) @ 35 *thumb1_movsi_insn/7 [length = 2]
+ and r4, r1 @ D.11539, bit @ 37 *thumb1_andsi3_insn [length = 2]
+ cmp r4, r2 @ D.11539, stateMask @ 38 cbranchsi4_insn/1 [length = 4]
+ bne .L6 @,
+ mov r4, #0 @ width, @ 7 *thumb1_movsi_insn/2 [length = 2]
+.L7:
+ ldr r5, [r0] @ D.11539, *port_7(D) @ 48 *thumb1_movsi_insn/7 [length = 2]
+ and r5, r1 @ D.11539, bit @ 50 *thumb1_andsi3_insn [length = 2]
+ cmp r5, r2 @ D.11539, stateMask @ 51 cbranchsi4_insn/1 [length = 4]
+ bne .L13 @,
+ add r4, r4, #1 @ width, @ 43 *thumb1_addsi3/1 [length = 2]
+ cmp r4, r3 @ width, maxloops @ 44 cbranchsi4_insn/1 [length = 4]
+ bne .L7 @,
+ mov r0, #0 @ D.11539, @ 11 *thumb1_movsi_insn/2 [length = 2]
+ b .L3 @ @ 130 *thumb_jump [length = 2]
+.L13:
+ mov r0, r4 @ D.11539, width @ 9 *thumb1_movsi_insn/1 [length = 2]
+ b .L3 @ @ 132 *thumb_jump [length = 2]
+.L10:
+ mov r0, r3 @ D.11539, maxloops @ 8 *thumb1_movsi_insn/1 [length = 2]
+.L3:
+ @ sp needed @ @ 115 force_register_use [length = 0]
+ pop {r4, r5, pc}
+ .size countPulseASM, .-countPulseASM
+ .ident "GCC: (GNU Tools for ARM Embedded Processors (Arduino build)) 4.8.3 20140228 (release) [ARM/embedded-4_8-branch revision 208322]"