/
main.c
95 lines (84 loc) · 2.75 KB
/
main.c
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
/*
Copyright (c) 2015, Augusto Fraga Giachero
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of the <organization> nor the
names of its contributors may be used to endorse or promote products
derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL AUGUSTO FRAGA GIACHERO BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Blink a LED
*/
#include "stm32f103xb.h"
/*
* Delay function:
* Uses the SysTick timer to wait for
* an arbitrary time in microseconds.
*
* The clock source is assumed to be
* the internal 8MHz RC oscillator
* divided by 8 (1MHz)
*/
void delay_us(unsigned int time)
{
/*
* Load the delay period in microseconds
* assuming a 1MHz source
*/
SysTick->LOAD = time;
/*
* Clears the current value and the count flag
*/
SysTick->VAL = 0;
/*
* Waits until the count ends
*/
while(!(SysTick->CTRL & SysTick_CTRL_COUNTFLAG_Msk));
}
int main()
{
/*
* Enable all Ports and Alternate Function clocks
*/
RCC->APB2ENR |= RCC_APB2ENR_IOPAEN | RCC_APB2ENR_IOPBEN |
RCC_APB2ENR_IOPCEN | RCC_APB2ENR_IOPDEN | RCC_APB2ENR_AFIOEN;
/*
* Disable JTAG and SWO (Free PB3, PB4 and PA15)
*/
AFIO->MAPR = AFIO_MAPR_SWJ_CFG_JTAGDISABLE;
/*
* Enable the SysTick Timer with
* the CPU clock divided by 8
*/
SysTick->CTRL = SysTick_CTRL_ENABLE_Msk;
/*
* Enable the PA1 as a digital output
*/
GPIOA->CRL = 0x00000020;
/*
* Infinite loop
*/
while(1)
{
GPIOA->BSRR = GPIO_BSRR_BS1; //PA1 = 1 (Led OFF)
delay_us(500000); //500ms delay
GPIOA->BSRR = GPIO_BSRR_BR1; //PA1 = 0 (Led ON)
delay_us(500000); //500ms delay
}
}