51 lines
1.6 KiB
C
51 lines
1.6 KiB
C
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#include <stm32f4xx.h>
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#include "misc.h"
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#include "systick.h"
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volatile uint32_t sys_tick_counter;
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void sys_tick_init() {
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// sys-tick interrupt called at 1ms intervals
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sys_tick_counter = 0;
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SysTick_Config(SystemCoreClock / 1000);
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}
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// called on SysTick interrupt
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void SysTick_Handler() {
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sys_tick_counter++;
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}
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void sys_tick_delay_ms(uint32_t delay_ms) {
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sys_tick_wait_at_least(sys_tick_counter, delay_ms);
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}
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// waits until at least delay_ms milliseconds have passed from the sampling of sys_tick_counter in stc
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// handles overflow properl
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// assumes stc was taken from sys_tick_counter some time before calling this function
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// eg stc <= sys_tick_counter for the case of no wrap around of sys_tick_counter
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void sys_tick_wait_at_least(uint32_t stc, uint32_t delay_ms) {
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// stc_wait is the value of sys_tick_counter that we wait for
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uint32_t stc_wait = stc + delay_ms;
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if (stc_wait < stc) {
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// stc_wait wrapped around
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while (stc <= sys_tick_counter || sys_tick_counter < stc_wait) {
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}
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} else {
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// stc_wait did not wrap around
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while (stc <= sys_tick_counter && sys_tick_counter < stc_wait) {
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}
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}
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}
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bool sys_tick_has_passed(uint32_t stc, uint32_t delay_ms) {
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// stc_wait is the value of sys_tick_counter that we wait for
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uint32_t stc_wait = stc + delay_ms;
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if (stc_wait < stc) {
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// stc_wait wrapped around
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return !(stc <= sys_tick_counter || sys_tick_counter < stc_wait);
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} else {
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// stc_wait did not wrap around
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return !(stc <= sys_tick_counter && sys_tick_counter < stc_wait);
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}
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}
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