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sam: Optimized delayMicroseconds() (Rob Tillaart)

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See #1121
This commit is contained in:
Cristian Maglie
2013-12-30 12:17:50 +01:00
parent 660c7d86fd
commit 825d8c8455
2 changed files with 3 additions and 1 deletions
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1
build/shared/revisions.txt
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@ -11,6 +11,7 @@ ARDUINO 1.5.6 BETA
[core] [core]
* sam: Fixed wrap-around bug in delay() (Mark Tillotson) * sam: Fixed wrap-around bug in delay() (Mark Tillotson)
* sam: Fixed regression in analogRead() (fails to read multiple channels) (Mark Tillotson) * sam: Fixed regression in analogRead() (fails to read multiple channels) (Mark Tillotson)
* sam: Optimized delayMicroseconds() (Rob Tillaart) #1121
* Optimized Print::print(String&) method, now uses internal string buffer to perform block write * Optimized Print::print(String&) method, now uses internal string buffer to perform block write
ARDUINO 1.5.5 BETA 2013.11.28 ARDUINO 1.5.5 BETA 2013.11.28

3
hardware/arduino/sam/cores/arduino/wiring.h
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@ -64,11 +64,12 @@ extern void delay( uint32_t dwMs ) ;
*/ */
static inline void delayMicroseconds(uint32_t) __attribute__((always_inline, unused)); static inline void delayMicroseconds(uint32_t) __attribute__((always_inline, unused));
static inline void delayMicroseconds(uint32_t usec){ static inline void delayMicroseconds(uint32_t usec){
if (usec == 0) return;
uint32_t n = usec * (VARIANT_MCK / 3000000); uint32_t n = usec * (VARIANT_MCK / 3000000);
asm volatile( asm volatile(
"L_%=_delayMicroseconds:" "\n\t" "L_%=_delayMicroseconds:" "\n\t"
"subs %0, #1" "\n\t" "subs %0, #1" "\n\t"
"bge L_%=_delayMicroseconds" "\n" "bne L_%=_delayMicroseconds" "\n"
: "+r" (n) : : "+r" (n) :
); );
} }