demo: More precise timing, using TIM6

Overflows in 6.5536 seconds

Signed-off-by: Amir Hammad <amir.hammad@hotmail.com>

1 files changed, 38 insertions, 6 deletions

diff --git a/src/demo.c b/src/demo.c
index 34c2f5b..d1f2d84 100644
--- a/src/demo.c
+++ b/src/demo.c
@@ -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;