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STM32 F7: Fix input clock source to SysTick

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This commit is contained in:
Gregory Nutt 2015-07-17 16:38:47 -06:00
parent 6f5aa9ae21
commit cbaf241078
1 changed files with 26 additions and 14 deletions
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40
arch/arm/src/stm32f7/stm32_timerisr.c
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@ -56,23 +56,29 @@
* Pre-processor Definitions
****************************************************************************/
/* Select MCU-specific settings
/* Select MCU-specific settings
*
* The SysTick timer is driven by the output of the Mast Clock Controller
* prescaler output (i.e., the MDIV output divider is not applied so that
* the driving frequency is the same as the CPU frequency).
* The RCC feeds the external clock of the Cortex System Timer (SysTick) with
* the AHB clock (HCLK) divided by 8. The SysTick can work either with this
* clock or with the Cortex clock (HCLK), configurable in the SysTick control
* and status register.
*
* The SysTick calibration value is fixed to 37500 which allows the generation
* of a time base of 1 ms with SysTick clock to the maximum frequency on
* MCK divided by 8. (?)
* The SysTick calibration value is fixed to 18750, which gives a reference
* time base of 1 ms with the SysTick clock set to 18.75 MHz (HCLK/8, with
* HCLK set to 150 MHz).
*/
#define STM32_SYSTICK_CLOCK BOARD_CPU_FREQUENCY
#define STM32_SYSTICK_CLOCK (STM32_BOARD_HCLK / 8)
/* The desired timer interrupt frequency is provided by the definition
* CLK_TCK (see include/time.h). CLK_TCK defines the desired number of
* system clock ticks per second. That value is a user configurable setting
* that defaults to 100 (100 ticks per second = 10 MS interval).
*
* For example, suppose HCLK = 216 MHz and CLK_TCK = 100, then:
*
* STM32_SYSTICK_CLOCK = 216 MHz / 8 = 27 MHz
* SYSTICK_RELOAD = (27,000,000 / 100) - 1 = 269,999
*/
#define SYSTICK_RELOAD ((STM32_SYSTICK_CLOCK / CLK_TCK) - 1)
@ -108,10 +114,10 @@
int up_timerisr(int irq, uint32_t *regs)
{
/* Process timer interrupt */
/* Process timer interrupt */
sched_process_timer();
return 0;
sched_process_timer();
return 0;
}
/****************************************************************************
@ -136,10 +142,16 @@ void up_timer_initialize(void)
(void)irq_attach(STM32_IRQ_SYSTICK, (xcpt_t)up_timerisr);
/* Enable SysTick interrupts (no divide-by-8) */
/* Enable SysTick interrupts:
*
* NVIC_SYSTICK_CTRL_CLKSOURCE=0 : Use the implementation defined clock
* source which, for the STM32F7, will be
* HCLK/8
* NVIC_SYSTICK_CTRL_TICKINT=1 : Generate interrupts
* NVIC_SYSTICK_CTRL_ENABLE : Enable the counter
*/
regval = (NVIC_SYSTICK_CTRL_CLKSOURCE | NVIC_SYSTICK_CTRL_TICKINT |
NVIC_SYSTICK_CTRL_ENABLE);
regval = (NVIC_SYSTICK_CTRL_TICKINT | NVIC_SYSTICK_CTRL_ENABLE);
putreg32(regval, NVIC_SYSTICK_CTRL);
/* And enable the timer interrupt */