forked from mirrors/qmk_firmware
Improve avr wait_us() (#16879)
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1 changed files with 29 additions and 9 deletions
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@ -17,6 +17,26 @@
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#include <util/delay.h>
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// http://ww1.microchip.com/downloads/en/devicedoc/atmel-0856-avr-instruction-set-manual.pdf
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// page 22: Table 4-2. Arithmetic and Logic Instructions
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/*
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for (uint16_t i = times; i > 0; i--) {
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__builtin_avr_delay_cycles(1);
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}
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.L3: sbiw r24,0 // loop step 1
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brne .L4 // loop step 2
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ret
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.L4: nop // __builtin_avr_delay_cycles(1);
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sbiw r24,1 // loop step 3
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rjmp .L3 // loop step 4
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*/
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#define AVR_sbiw_clocks 2
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#define AVR_rjmp_clocks 2
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#define AVR_brne_clocks 2
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#define AVR_WAIT_LOOP_OVERHEAD (AVR_sbiw_clocks + AVR_brne_clocks + AVR_sbiw_clocks + AVR_rjmp_clocks)
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#define wait_ms(ms) \
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do { \
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if (__builtin_constant_p(ms)) { \
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@ -27,15 +47,15 @@
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} \
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} \
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} while (0)
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#define wait_us(us) \
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do { \
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if (__builtin_constant_p(us)) { \
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_delay_us(us); \
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} else { \
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for (uint16_t i = us; i > 0; i--) { \
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_delay_us(1); \
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} \
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} \
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#define wait_us(us) \
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do { \
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if (__builtin_constant_p(us)) { \
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_delay_us(us); \
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} else { \
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for (uint16_t i = us; i > 0; i--) { \
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__builtin_avr_delay_cycles((F_CPU / 1000000) - AVR_WAIT_LOOP_OVERHEAD); \
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} \
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} \
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} while (0)
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#define wait_cpuclock(n) __builtin_avr_delay_cycles(n)
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#define CPU_CLOCK F_CPU
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