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clock.c
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clock.c
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/*
* Copyright (C) 2013 Chuck McManis <cmcmanis@mcmanis.com>
*
* Simple clock setup/driver for the STM32F4-Discovery board.
* libopencm3 does the heavy lifting, it just sets up SysTick
* and the desired clock rate (168Mhz in this case)
*/
#include <libopencm3/stm32/rcc.h>
#include <libopencm3/cm3/nvic.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/cm3/systick.h>
#include <stdint.h>
#include "clock.h"
/*
* Comment this #define out if you don't want the BLUE led on
* the board blinking at 2Hz
*/
#define SYSTICK_HEARTBEAT
/*
* SysTick support routines
*/
/* monotonically increasing number of milliseconds from reset
* overflows every 49 days if you're wondering
*/
volatile uint32_t system_millis;
/* Called when systick fires */
void
sys_tick_handler(void) {
system_millis++;
#ifdef SYSTICK_HEARTBEAT
/* Generate a 2Hz heart beep blink */
if ((system_millis % 500) == 0) {
gpio_toggle(GPIOD, GPIO15); // BLUE led
}
#endif
}
/* sleep for delay milliseconds */
void msleep(uint32_t delay) {
uint32_t wake = system_millis + delay;
while (wake > system_millis) ;
}
/* return the time */
uint32_t mtime() {
return system_millis;
}
/* Set up a timer to create 1mS ticks. */
static void
systick_setup(int tick_rate) {
/* clock rate / 1000 to get 1mS interrupt rate */
systick_set_reload((168000000) / tick_rate);
STK_CTRL = 0x07;
#if 0
/* libopencm3 bug, the above assign does all three of these
* steps, but systick_set_clocksource fails to set the clock
* source to AHB because it doesn't correctly shift the value
*/
systick_set_clocksource(1);
systick_counter_enable();
systick_interrupt_enable();
#endif
}
/* Set STM32 to 168 MHz. */
void
clock_init(int systick_rate)
{
rcc_clock_setup_hse_3v3(&hse_8mhz_3v3[CLOCK_3V3_168MHZ]);
#ifdef SYSTICK_HEARTBEAT
rcc_peripheral_enable_clock(&RCC_AHB1ENR, RCC_AHB1ENR_IOPDEN);
gpio_mode_setup(GPIOD, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO15);
#endif
if (systick_rate) {
systick_setup(systick_rate);
}
}