aboutsummaryrefslogtreecommitdiff
path: root/examples/other/timer_interrupt/timer.c
blob: f88de8628088d139a57b41b678f37955fa7dcc05 (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
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
/*
 * This file is part of the libopenstm32 project.
 *
 * Copyright (C) 2010 Thomas Otto <tommi@viadmin.org>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <libopenstm32/rcc.h>
#include <libopenstm32/flash.h>
#include <libopenstm32/gpio.h>
#include <libopenstm32/usart.h>
#include <libopenstm32/timer.h>
#include <libopenstm32/nvic.h>

/* Set STM32 to 72 MHz. HSE 16MHz */
void clock_setup(void)
{
        /* enable Internal High Speed Oscillator */
        rcc_osc_on(HSI);
        rcc_wait_for_osc_ready(HSI);

        /* Select HSI as SYSCLK source. */
        rcc_set_sysclk_source(SW_SYSCLKSEL_HSICLK);

        /* enable External High Speed Oscillator 16MHz */
        rcc_osc_on(HSE);
        rcc_wait_for_osc_ready(HSE);
        rcc_set_sysclk_source(SW_SYSCLKSEL_HSECLK);

        /* set prescalers for ADC, ABP1, ABP2...  make this before touching the PLL */
        rcc_set_hpre(HPRE_SYSCLK_NODIV); //prescales the AHB clock from the SYSCLK
        rcc_set_adcpre(ADCPRE_PLCK2_DIV6); //prescales the ADC from the APB2 clock; max 14MHz
        rcc_set_ppre1(PPRE1_HCLK_DIV2); //prescales the APB1 from the AHB clock; max 36MHz
        rcc_set_ppre2(PPRE2_HCLK_NODIV); //prescales the APB2 from the AHB clock; max 72MHz

        /* sysclk should run with 72MHz -> 2 Waitstates ; choose 0WS from 0-24MHz, 1WS from 24-48MHz, 2WS from 48-72MHz */
        flash_set_ws(FLASH_LATENCY_2WS);

        /* Set the PLL multiplication factor to 9. -> 16MHz (external) * 9 (multiplier) / 2 (PLLXTPRE_HSE_CLK_DIV2) = 72MHz */
        rcc_set_pll_multiplication_factor(PLLMUL_PLL_CLK_MUL9);

        /* Select HSI as PLL source. */
        rcc_set_pll_source(PLLSRC_HSE_CLK);

        /* divide external frequency by 2 before entering pll (only valid/needed for HSE) */
        rcc_set_pllxtpre(PLLXTPRE_HSE_CLK_DIV2);

        /* Enable PLL oscillator and wait for it to stabilize. */
        rcc_osc_on(PLL);
        rcc_wait_for_osc_ready(PLL);

        /* Select PLL as SYSCLK source. */
        rcc_set_sysclk_source(SW_SYSCLKSEL_PLLCLK);
}

void gpio_setup(void)
{
	/* Enable GPIOB clock. */
	rcc_peripheral_enable_clock(&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);
}

void nvic_setup()
{
	/* 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()
{
	/* LED2 on/off */
	gpio_toggle(GPIOB, GPIO6);

	/* clear interrrupt flag */
	TIM_SR(TIM2) &= ~TIM_SR_UIF;
}

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

	gpio_clear(GPIOB, GPIO7);	/* LED1 on */
	gpio_set(GPIOB, GPIO6);		/* LED2 off */
	
	rcc_peripheral_enable_clock(&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 value 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;
}