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[EXAMPLE:F0] Add example of using systick and MCO output on pin PA9.

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This example is a merge of Chuck McManis's example for F4 and onnokort's system clock setting test blink example for demonstration issue, corrected in #224.

The LED in any available clock setting flashes four times per second.
This commit is contained in:
Frantisek Burian
2013-12-15 00:35:19 +01:00
committed by Piotr Esden-Tempski
parent c5d6480201
commit d8757ab1fc
3 changed files with 116 additions and 0 deletions
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examples/stm32/f0/stm32f0-discovery/systick_blink/Makefile Normal file
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##
## This file is part of the libopencm3 project.
##
## Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
##
## 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/>.
##
BINARY = systick_blink
LDSCRIPT = ../stm32f0-discovery.ld
include ../../Makefile.include

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examples/stm32/f0/stm32f0-discovery/systick_blink/README Normal file
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------------------------------------------------------------------------------
README
------------------------------------------------------------------------------
This example is the same as fancy_blink except that it uses the systick timer
to generate time accurate delays. The blue LED flashes four times per second.
On pin PA9, there is MCO output of internal reference clock. This can be used
to debug the PLL clock setup by scope.

83
examples/stm32/f0/stm32f0-discovery/systick_blink/systick_blink.c Normal file
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/*
* This file is part of the libopencm3 project.
*
* Copyright (C) 2013 Chuck McManis <cmcmanis@mcmanis.com>
* Copyright (C) 2013 Onno Kortmann <onno@gmx.net>
* Copyright (C) 2013 Frantisek Burian <BuFran@seznam.cz> (merge)
*
* 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/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/cm3/nvic.h>
#include <libopencm3/cm3/systick.h>
/* Called when systick fires */
void sys_tick_handler(void)
{
gpio_toggle(GPIOC, GPIO8);
}
/* Set up timer to fire freq times per second */
static void systick_setup(int freq)
{
systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
/* clear counter so it starts right away */
STK_CVR=0;
systick_set_reload(rcc_core_frequency / freq);
systick_counter_enable();
systick_interrupt_enable();
}
/* set STM32 to clock by 48MHz from HSI oscillator */
static void clock_setup(void)
{
rcc_clock_setup_in_hsi_out_48mhz();
/* Enable clocks to the GPIO subsystems */
rcc_periph_clock_enable(RCC_GPIOC);
rcc_periph_clock_enable(RCC_GPIOA);
}
static void gpio_setup(void)
{
/* Select pin functions. PC8/PC9 are the two LEDs on the
STM32F0DISCOVERY board. */
gpio_mode_setup(GPIOC, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO8 | GPIO9);
/* set GPIOA to AF 0 */
gpio_mode_setup(GPIOA, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO8);
}
static void mco_setup(void)
{
/* Enable system clock output on pin PA8 (so it can be checked with a
scope) */
rcc_set_mco(RCC_CFGR_MCO_SYSCLK);
}
int main(void)
{
clock_setup();
gpio_setup();
mco_setup();
/* setup systick to generate 2 LED flashes per second */
systick_setup(8);
/* Do nothing in main loop */
while(1);
}