aboutsummaryrefslogtreecommitdiff
path: root/examples/stm32/f1/other/timer_interrupt/timer.c
blob: d4df023ad2f6ab66c60b81760d104a3232e119ac (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
/*
 * This file is part of the libopencm3 project.
 *
 * Copyright (C) 2010 Thomas Otto <tommi@viadmin.org>
 *
 * This library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <libopencm3/stm32/f1/rcc.h>
#include <libopencm3/stm32/f1/flash.h>
#include <libopencm3/stm32/f1/gpio.h>
#include <libopencm3/stm32/timer.h>
#include <libopencm3/cm3/nvic.h>

static void gpio_setup(void)
{
	/* Enable GPIOB clock. */
	rcc_peripheral_enable_clock(&RCC_APB2ENR, RCC_APB2ENR_IOPBEN);

	/* Set GPIO6/7 (in GPIO port B) to 'output push-pull' for the LEDs. */
	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_2_MHZ,
		      GPIO_CNF_OUTPUT_PUSHPULL, GPIO6);
	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_2_MHZ,
		      GPIO_CNF_OUTPUT_PUSHPULL, GPIO7);
}

static void nvic_setup(void)
{
	/* Without this the timer interrupt routine will never be called. */
	nvic_enable_irq(NVIC_TIM2_IRQ);
	nvic_set_priority(NVIC_TIM2_IRQ, 1);
}

void tim2_isr(void)
{
	gpio_toggle(GPIOB, GPIO6);   /* LED2 on/off. */
	TIM_SR(TIM2) &= ~TIM_SR_UIF; /* Clear interrrupt flag. */
}

int main(void)
{
	rcc_clock_setup_in_hse_16mhz_out_72mhz();
	gpio_setup();
	nvic_setup();

	gpio_clear(GPIOB, GPIO7);	/* LED1 on */
	gpio_set(GPIOB, GPIO6);		/* LED2 off */

	rcc_peripheral_enable_clock(&RCC_APB1ENR, RCC_APB1ENR_TIM2EN);

	/*
	 * The goal is to let the LED2 glow for a second and then be
	 * off for a second.
	 */

	/* Set timer start value. */
	TIM_CNT(TIM2) = 1;

	/* Set timer prescaler. 72MHz/1440 => 50000 counts per second. */
	TIM_PSC(TIM2) = 1440;

	/* End timer value. If this is reached an interrupt is generated. */
	TIM_ARR(TIM2) = 50000;

	/* Update interrupt enable. */
	TIM_DIER(TIM2) |= TIM_DIER_UIE;

	/* Start timer. */
	TIM_CR1(TIM2) |= TIM_CR1_CEN;

	while (1); /* Halt. */

	return 0;
}