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Improve avr wait_us() (#16879)

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Takeshi ISHII 2022-08-14 08:04:03 +09:00 committed by GitHub
parent 2f87abd4ef
commit a83afb3fcd
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1 changed files with 29 additions and 9 deletions
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22
platforms/avr/_wait.h
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@ -17,6 +17,26 @@
#include <util/delay.h>
// http://ww1.microchip.com/downloads/en/devicedoc/atmel-0856-avr-instruction-set-manual.pdf
// page 22: Table 4-2. Arithmetic and Logic Instructions
/*
for (uint16_t i = times; i > 0; i--) {
__builtin_avr_delay_cycles(1);
}
.L3: sbiw r24,0 // loop step 1
brne .L4 // loop step 2
ret
.L4: nop // __builtin_avr_delay_cycles(1);
sbiw r24,1 // loop step 3
rjmp .L3 // loop step 4
*/
#define AVR_sbiw_clocks 2
#define AVR_rjmp_clocks 2
#define AVR_brne_clocks 2
#define AVR_WAIT_LOOP_OVERHEAD (AVR_sbiw_clocks + AVR_brne_clocks + AVR_sbiw_clocks + AVR_rjmp_clocks)
#define wait_ms(ms) \
do { \
if (__builtin_constant_p(ms)) { \
@ -33,7 +53,7 @@
_delay_us(us); \
} else { \
for (uint16_t i = us; i > 0; i--) { \
_delay_us(1); \
__builtin_avr_delay_cycles((F_CPU / 1000000) - AVR_WAIT_LOOP_OVERHEAD); \
} \
} \
} while (0)