diff options
Diffstat (limited to 'src/stm32f0/timer.c')
| -rw-r--r-- | src/stm32f0/timer.c | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/src/stm32f0/timer.c b/src/stm32f0/timer.c new file mode 100644 index 00000000..e5628f93 --- /dev/null +++ b/src/stm32f0/timer.c @@ -0,0 +1,156 @@ +/* + * Timer and PWM functions for STM32F042 boards. + * Also replacement for 'generic/armcm_timer.c', which not compatible + * with Cortex-M0 CPUs + * + * Copyright (C) 2019 Eug Krashtan <eug.krashtan@gmail.com> + * This file may be distributed under the terms of the GNU GPLv3 license. + * + * DO NOT USE HAL! (Timer HAL extremely fat) + */ + +#include "autoconf.h" // CONFIG_CLOCK_FREQ +#include "board/internal.h" // SysTick +#include "board/irq.h" // irq_disable +#include "stm32f0xx.h" +#include "log.h" +#include "sched.h" // DECL_INIT +#include "command.h" // shutdown + +DECL_CONSTANT("CLOCK_FREQ", CONFIG_CLOCK_FREQ); + +// Return the number of clock ticks for a given number of microseconds +uint32_t +timer_from_us(uint32_t us) +{ + return us * (CONFIG_CLOCK_FREQ / 1000000); +} + +// Return true if time1 is before time2. Always use this function to +// compare times as regular C comparisons can fail if the counter +// rolls over. +uint8_t +timer_is_before(uint32_t time1, uint32_t time2) +{ + return (int32_t)(time1 - time2) < 0; +} + +// Set the next irq time +static void +timer_set_diff(uint32_t value) +{ + SysTick->LOAD = value; + SysTick->VAL = 0; + SysTick->LOAD = 0; +} + +// Activate timer dispatch as soon as possible +void +timer_kick(void) +{ + SysTick->LOAD = 0; + SysTick->VAL = 0; + SCB->ICSR = SCB_ICSR_PENDSTSET_Msk; +} + +/* + * TIM2 (32bit) used instead of DWT->CYCCNT in original variant + */ +void TimerInit(void) +{ + RCC->APB1ENR |= RCC_APB1ENR_TIM2EN; + + TIM2->PSC = 0; + //TIM2->ARR = 0xFFFFFFFF; reset value + TIM2->DIER = TIM_DIER_UIE; + TIM2->CR1 = TIM_CR1_CEN; + + NVIC_EnableIRQ(TIM2_IRQn); + + // Enable SysTick + irqstatus_t flag = irq_save(); + NVIC_SetPriority(SysTick_IRQn, 2); + SysTick->CTRL = (SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_TICKINT_Msk + | SysTick_CTRL_ENABLE_Msk); + timer_kick(); + irq_restore(flag); + +} +DECL_INIT(TimerInit); + +uint32_t +timer_read_time(void) +{ + return TIM2->CNT; +} + +static uint32_t timer_repeat_until; +#define TIMER_IDLE_REPEAT_TICKS timer_from_us(500) +#define TIMER_REPEAT_TICKS timer_from_us(100) + +#define TIMER_MIN_TRY_TICKS timer_from_us(2) +#define TIMER_DEFER_REPEAT_TICKS timer_from_us(5) + +// Invoke timers +static uint32_t +timer_dispatch_many(void) +{ + uint32_t tru = timer_repeat_until; + for (;;) { + // Run the next software timer + uint32_t next = sched_timer_dispatch(); + + uint32_t now = timer_read_time(); + int32_t diff = next - now; + if (diff > (int32_t)TIMER_MIN_TRY_TICKS) + // Schedule next timer normally. + return diff; + + if (unlikely(timer_is_before(tru, now))) { + // Check if there are too many repeat timers + if (diff < (int32_t)(-timer_from_us(1000))) + try_shutdown("Rescheduled timer in the past"); + if (sched_tasks_busy()) { + timer_repeat_until = now + TIMER_REPEAT_TICKS; + return TIMER_DEFER_REPEAT_TICKS; + } + timer_repeat_until = tru = now + TIMER_IDLE_REPEAT_TICKS; + } + + // Next timer in the past or near future - wait for it to be ready + irq_enable(); + while (unlikely(diff > 0)) + diff = next - timer_read_time(); + irq_disable(); + } +} + +// IRQ handler +void __visible __aligned(16) // aligning helps stabilize perf benchmarks +SysTick_Handler(void) +{ + irq_disable(); + uint32_t diff = timer_dispatch_many(); + timer_set_diff(diff); + irq_enable(); +} + +// Make sure timer_repeat_until doesn't wrap 32bit comparisons +void +timer_task(void) +{ + uint32_t now = timer_read_time(); + irq_disable(); + if (timer_is_before(timer_repeat_until, now)) + timer_repeat_until = now; + irq_enable(); +} +DECL_TASK(timer_task); + + +void TIM2_IRQHandler(void) +{ + if(TIM2->SR & TIM_SR_UIF) { + TIM2->SR &= ~TIM_SR_UIF; // clear UIF flag + } +} |