3ef44bff54
Fix the reload value in the examples: to get a SysTick interrupt every N clock pulses: set reload to N-1 see http://infocenter.arm.com/help/topic/com.arm.doc.dui0552a/BGBEEJHC.html#BABGACGG
83 lines
2.3 KiB
C
83 lines
2.3 KiB
C
/*
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* This file is part of the libopencm3 project.
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*
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* Copyright (C) 2012 Piotr Esden-Tempski <piotr@esden.net>
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*
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* This library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <libopencm3/stm32/f1/rcc.h>
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#include <libopencm3/stm32/f1/flash.h>
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#include <libopencm3/stm32/f1/gpio.h>
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#include <libopencm3/cm3/nvic.h>
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#include <libopencm3/cm3/systick.h>
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u32 temp32;
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void gpio_setup(void)
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{
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/* Enable alternate function peripheral clock. */
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rcc_peripheral_enable_clock(&RCC_APB2ENR, RCC_APB2ENR_AFIOEN);
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/* Enable GPIOB clock. */
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rcc_peripheral_enable_clock(&RCC_APB2ENR, RCC_APB2ENR_IOPBEN);
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gpio_clear(GPIOB, GPIO4); /* LED green on */
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gpio_set(GPIOB, GPIO5); /* LED red off */
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/* Set GPIO4/5 (in GPIO port B) to 'output push-pull' for the LEDs. */
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gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ,
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GPIO_CNF_OUTPUT_PUSHPULL, GPIO4);
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gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ,
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GPIO_CNF_OUTPUT_PUSHPULL, GPIO5);
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AFIO_MAPR |= AFIO_MAPR_SWJ_CFG_FULL_SWJ_NO_JNTRST;
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}
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void sys_tick_handler(void)
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{
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temp32++;
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/* We call this handler every 1ms so 1000ms = 1s on/off. */
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if (temp32 == 1000) {
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gpio_toggle(GPIOB, GPIO4); /* LED green on/off */
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gpio_toggle(GPIOB, GPIO5); /* LED red on/off */
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temp32 = 0;
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}
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}
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int main(void)
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{
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rcc_clock_setup_in_hsi_out_64mhz();
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gpio_setup();
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temp32 = 0;
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/* 64MHz / 8 => 8000000 counts per second */
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systick_set_clocksource(STK_CTRL_CLKSOURCE_AHB_DIV8);
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/* 8000000/8000 = 1000 overflows per second - every 1ms one interrupt */
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/* SysTick interrupt every N clock pulses: set reload to N-1 */
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systick_set_reload(7999);
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systick_interrupt_enable();
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/* Start counting. */
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systick_counter_enable();
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while (1); /* Halt. */
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return 0;
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}
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