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demo: More precise timing, using TIM6

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Overflows in 6.5536 seconds

Signed-off-by: Amir Hammad <amir.hammad@hotmail.com>
This commit is contained in:
Amir Hammad 2015-04-01 19:08:53 +02:00
parent e35c1e9fc6
commit ae3449a302
1 changed files with 38 additions and 6 deletions
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44
src/demo.c
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@ -39,6 +39,7 @@
#include <string.h>
#include <stdlib.h>
static inline void delay_ms_busy_loop(uint32_t ms)
{
volatile uint32_t i;
@ -61,6 +62,29 @@ static void clock_setup(void)
rcc_periph_clock_enable(RCC_USART6); // USART
rcc_periph_clock_enable(RCC_OTGFS); // OTG_FS
rcc_periph_clock_enable(RCC_OTGHS); // OTG_HS
rcc_periph_clock_enable(RCC_TIM6); // TIM6
}
/*
* setup 10kHz timer
*/
static void tim6_setup(void)
{
timer_reset(TIM6);
timer_set_prescaler(TIM6, 16800 - 1); // 168Mhz/10000hz - 1
timer_set_period(TIM6, 65535); // Overflow in ~6.5 seconds
timer_enable_counter(TIM6);
}
static uint32_t tim6_get_time_us(void)
{
uint32_t cnt = timer_get_counter(TIM6);
// convert to 1MHz less precise timer value -> units: microseconds
uint32_t time_us = cnt * 100;
return time_us;
}
static void gpio_setup(void)
@ -140,6 +164,9 @@ int main(void)
clock_setup();
gpio_setup();
// provides time_curr_us to usbh_poll function
tim6_setup();
#ifdef USART_DEBUG
usart_init(USART6, 921600);
#endif
@ -168,18 +195,23 @@ int main(void)
LOG_PRINTF("USB init complete\r\n");
uint32_t i = 0;
LOG_FLUSH();
while (1) {
LOG_FLUSH();
// Toggle some led
// set busy led
gpio_set(GPIOD, GPIO14);
usbh_poll(i);
uint32_t time_curr_us = tim6_get_time_us();
usbh_poll(time_curr_us);
// clear busy led
gpio_clear(GPIOD, GPIO14);
LOG_FLUSH();
// approx 1ms interval between usbh_poll()
delay_ms_busy_loop(1);
i += 1000;
}
return 0;