pulseIn: add ASM implementation for Due

Author: facchinm

platform.txt

@@ -22,7 +22,8 @@ compiler.c.cmd=arm-none-eabi-gcc
 compiler.c.flags=-c -g -Os {compiler.warning_flags} -ffunction-sections -fdata-sections -nostdlib --param max-inline-insns-single=500 -Dprintf=iprintf -MMD
 compiler.c.elf.cmd=arm-none-eabi-gcc
 compiler.c.elf.flags=-Os -Wl,--gc-sections
-compiler.S.flags=-c -g -x assembler-with-cpp
+compiler.S.cmd=arm-none-eabi-gcc
+compiler.S.flags=-c -g -x assembler-with-cpp -mthumb
 compiler.cpp.cmd=arm-none-eabi-g++
 compiler.cpp.flags=-c -g -Os {compiler.warning_flags} -ffunction-sections -fdata-sections -nostdlib -fno-threadsafe-statics --param max-inline-insns-single=500 -fno-rtti -fno-exceptions -Dprintf=iprintf -MMD
 compiler.ar.cmd=arm-none-eabi-ar
@@ -42,6 +43,7 @@ build.extra_flags=
 compiler.c.extra_flags=
 compiler.c.elf.extra_flags=
 compiler.cpp.extra_flags=
+compiler.S.extra_flags=
 compiler.ar.extra_flags=
 compiler.elf2hex.extra_flags=
 
@@ -66,6 +68,9 @@ recipe.c.o.pattern="{compiler.path}{compiler.c.cmd}" {compiler.c.flags} -mcpu={b
 ## Compile c++ files
 recipe.cpp.o.pattern="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} -mcpu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.cpp.extra_flags} {build.extra_flags} {compiler.libsam.c.flags} {includes} "{source_file}" -o "{object_file}"
 
+## Compile S files
+recipe.S.o.pattern="{compiler.path}{compiler.S.cmd}" {compiler.S.flags} -mcpu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.S.extra_flags} {build.extra_flags} {compiler.libsam.c.flags} {includes} "{source_file}" -o "{object_file}"
+
 ## Create archives
 recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} {compiler.ar.extra_flags} "{build.path}/{archive_file}" "{object_file}"