stm32入门教程-- DMA数据转运

简介

原理

实验示例

1、DMA数据转运

实现代码

实验效果

原理

实验示例

1、DMA数据转运

接线图

存储器映像

我们在开始代码之前，可以看下我们定义的数据，到底是不是真的存储在了这个相应的地址区间里，我们看代码：

uint8_t aa= 0x66;
int main(void)
{
    OLED_Init();
    OLED_ShowHexNum(1,1,aa,2);
    OLED_ShowHexNum(1,1,(uint32_t)&aa,2);
}

aa=0x66，为一个十六进制的数，

第一行 OLED_ShowHexNum(1,1,aa,2);就是正常的定义变量，引用变量；

第二行我们引用变量的地址看看，&号放在aa前面，表示取这个变量的地址，然后，这个变量取地址之后，应该要存在一个指针变量里，这个如果想用数字显示，一定要在前面加一个强制类型转换（uint32_t),如果不加强制类型转换，就是指针跨级赋值了，编译时会出现警告，最后显示长度为8，8个十六进制的数，表示32位，32位的系统都是32位的。

编译显示如图

现在第一行显示的是aa变量的内容，66，

第二行显示的是aa这个变量，它被存储的地址，可以看到这个地址是2000 0000，地址是20开头的

对应表中aa这个变量，存储的位置是SRAM区，在SRAM它的地址肯定是20开头的，那它的具体地址是多少呢？这个是由编译器决定的，目前SRAM区还没什么东西，所以编译器就把这个变量放在了SRAM区的第一个位置，也就是2000 0000 ，

const uint8_t aa= 0x66;
int main(void)
{
    OLED_Init();
    OLED_ShowHexNum(1,1,aa,2);
    OLED_ShowHexNum(1,1,(uint32_t)&aa,2);
}

如果在变量前面，加一个const关键字，const是C语言的关键字，表示的是常量的意思，被const修饰的变量，在程序中只能读，不能写。

在前面简介和原理中有提到，Flash里的数据也是只能读不能写的，所以const和Flash就联系起来了。

在STM32中，使用const定义的变量，是存储在Flash里面的，这里就不应该说是变量了·而是常量，这个变量的值只能在定义的时候给，如果尝试在main函数中尝试去修改这个值，编译后是会报错的，错误的意思就是不能给const常量赋值。

编译下载后

我们可以看到aa这个地址就变成0800开头的了，由上图表可知，现在aa是被存储在了Flash里，在Flash里，存储的是程序代码，当然也有常量数据，图中的程序地址有一些往后偏移，这是因为Flash里面还有一些程序代码这些东西，放在了前面，所以编译器里常量安排的地址就相对靠后了一些，这个就是定义变量和常量的方法。

正常情况下，我们使用的都是常量，直接定义就行，不需要加const

那什么时候需要加const常量呢？

就是在当我们程序出现了一大批数据，并且不需要更改时，就可以把他定义成常量，这样就能节省SRAM的空间，比如查找表，字库数据等等。

#ifndef __OLED_FONT_H
#define __OLED_FONT_H

/*OLED字模库，宽8像素，高16像素*/
const uint8_t OLED_F8x16[][16]=
{
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//  0
	
	0x00,0x00,0x00,0xF8,0x00,0x00,0x00,0x00,
	0x00,0x00,0x00,0x33,0x30,0x00,0x00,0x00,//! 1
	
	0x00,0x10,0x0C,0x06,0x10,0x0C,0x06,0x00,
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//" 2
	
	0x40,0xC0,0x78,0x40,0xC0,0x78,0x40,0x00,
	0x04,0x3F,0x04,0x04,0x3F,0x04,0x04,0x00,//# 3
	
	0x00,0x70,0x88,0xFC,0x08,0x30,0x00,0x00,
	0x00,0x18,0x20,0xFF,0x21,0x1E,0x00,0x00,//$ 4
	
	0xF0,0x08,0xF0,0x00,0xE0,0x18,0x00,0x00,
	0x00,0x21,0x1C,0x03,0x1E,0x21,0x1E,0x00,//% 5
	
	0x00,0xF0,0x08,0x88,0x70,0x00,0x00,0x00,
	0x1E,0x21,0x23,0x24,0x19,0x27,0x21,0x10,//& 6
	
	0x10,0x16,0x0E,0x00,0x00,0x00,0x00,0x00,
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//' 7
	
	0x00,0x00,0x00,0xE0,0x18,0x04,0x02,0x00,
	0x00,0x00,0x00,0x07,0x18,0x20,0x40,0x00,//( 8
	
	0x00,0x02,0x04,0x18,0xE0,0x00,0x00,0x00,
	0x00,0x40,0x20,0x18,0x07,0x00,0x00,0x00,//) 9
	
	0x40,0x40,0x80,0xF0,0x80,0x40,0x40,0x00,
	0x02,0x02,0x01,0x0F,0x01,0x02,0x02,0x00,//* 10
	
	0x00,0x00,0x00,0xF0,0x00,0x00,0x00,0x00,
	0x01,0x01,0x01,0x1F,0x01,0x01,0x01,0x00,//+ 11
	
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
	0x80,0xB0,0x70,0x00,0x00,0x00,0x00,0x00,//, 12
	
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
	0x00,0x01,0x01,0x01,0x01,0x01,0x01,0x01,//- 13
	
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
	0x00,0x30,0x30,0x00,0x00,0x00,0x00,0x00,//. 14
	
	0x00,0x00,0x00,0x00,0x80,0x60,0x18,0x04,
	0x00,0x60,0x18,0x06,0x01,0x00,0x00,0x00,/// 15
	
	0x00,0xE0,0x10,0x08,0x08,0x10,0xE0,0x00,
	0x00,0x0F,0x10,0x20,0x20,0x10,0x0F,0x00,//0 16
	
	0x00,0x10,0x10,0xF8,0x00,0x00,0x00,0x00,
	0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,//1 17
	
	0x00,0x70,0x08,0x08,0x08,0x88,0x70,0x00,
	0x00,0x30,0x28,0x24,0x22,0x21,0x30,0x00,//2 18
	
	0x00,0x30,0x08,0x88,0x88,0x48,0x30,0x00,
	0x00,0x18,0x20,0x20,0x20,0x11,0x0E,0x00,//3 19
	
	0x00,0x00,0xC0,0x20,0x10,0xF8,0x00,0x00,
	0x00,0x07,0x04,0x24,0x24,0x3F,0x24,0x00,//4 20
	
	0x00,0xF8,0x08,0x88,0x88,0x08,0x08,0x00,
	0x00,0x19,0x21,0x20,0x20,0x11,0x0E,0x00,//5 21
	
	0x00,0xE0,0x10,0x88,0x88,0x18,0x00,0x00,
	0x00,0x0F,0x11,0x20,0x20,0x11,0x0E,0x00,//6 22
	
	0x00,0x38,0x08,0x08,0xC8,0x38,0x08,0x00,
	0x00,0x00,0x00,0x3F,0x00,0x00,0x00,0x00,//7 23
	
	0x00,0x70,0x88,0x08,0x08,0x88,0x70,0x00,
	0x00,0x1C,0x22,0x21,0x21,0x22,0x1C,0x00,//8 24
	
	0x00,0xE0,0x10,0x08,0x08,0x10,0xE0,0x00,
	0x00,0x00,0x31,0x22,0x22,0x11,0x0F,0x00,//9 25
	
	0x00,0x00,0x00,0xC0,0xC0,0x00,0x00,0x00,
	0x00,0x00,0x00,0x30,0x30,0x00,0x00,0x00,//: 26
	
	0x00,0x00,0x00,0x80,0x00,0x00,0x00,0x00,
	0x00,0x00,0x80,0x60,0x00,0x00,0x00,0x00,//; 27
	
	0x00,0x00,0x80,0x40,0x20,0x10,0x08,0x00,
	0x00,0x01,0x02,0x04,0x08,0x10,0x20,0x00,//< 28
	
	0x40,0x40,0x40,0x40,0x40,0x40,0x40,0x00,
	0x04,0x04,0x04,0x04,0x04,0x04,0x04,0x00,//= 29
	
	0x00,0x08,0x10,0x20,0x40,0x80,0x00,0x00,
	0x00,0x20,0x10,0x08,0x04,0x02,0x01,0x00,//> 30
	
	0x00,0x70,0x48,0x08,0x08,0x08,0xF0,0x00,
	0x00,0x00,0x00,0x30,0x36,0x01,0x00,0x00,//? 31
	
	0xC0,0x30,0xC8,0x28,0xE8,0x10,0xE0,0x00,
	0x07,0x18,0x27,0x24,0x23,0x14,0x0B,0x00,//@ 32
	
	0x00,0x00,0xC0,0x38,0xE0,0x00,0x00,0x00,
	0x20,0x3C,0x23,0x02,0x02,0x27,0x38,0x20,//A 33
	
	0x08,0xF8,0x88,0x88,0x88,0x70,0x00,0x00,
	0x20,0x3F,0x20,0x20,0x20,0x11,0x0E,0x00,//B 34
	
	0xC0,0x30,0x08,0x08,0x08,0x08,0x38,0x00,
	0x07,0x18,0x20,0x20,0x20,0x10,0x08,0x00,//C 35
	
	0x08,0xF8,0x08,0x08,0x08,0x10,0xE0,0x00,
	0x20,0x3F,0x20,0x20,0x20,0x10,0x0F,0x00,//D 36
	
	0x08,0xF8,0x88,0x88,0xE8,0x08,0x10,0x00,
	0x20,0x3F,0x20,0x20,0x23,0x20,0x18,0x00,//E 37
	
	0x08,0xF8,0x88,0x88,0xE8,0x08,0x10,0x00,
	0x20,0x3F,0x20,0x00,0x03,0x00,0x00,0x00,//F 38
	
	0xC0,0x30,0x08,0x08,0x08,0x38,0x00,0x00,
	0x07,0x18,0x20,0x20,0x22,0x1E,0x02,0x00,//G 39
	
	0x08,0xF8,0x08,0x00,0x00,0x08,0xF8,0x08,
	0x20,0x3F,0x21,0x01,0x01,0x21,0x3F,0x20,//H 40
	
	0x00,0x08,0x08,0xF8,0x08,0x08,0x00,0x00,
	0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,//I 41
	
	0x00,0x00,0x08,0x08,0xF8,0x08,0x08,0x00,
	0xC0,0x80,0x80,0x80,0x7F,0x00,0x00,0x00,//J 42
	
	0x08,0xF8,0x88,0xC0,0x28,0x18,0x08,0x00,
	0x20,0x3F,0x20,0x01,0x26,0x38,0x20,0x00,//K 43
	
	0x08,0xF8,0x08,0x00,0x00,0x00,0x00,0x00,
	0x20,0x3F,0x20,0x20,0x20,0x20,0x30,0x00,//L 44
	
	0x08,0xF8,0xF8,0x00,0xF8,0xF8,0x08,0x00,
	0x20,0x3F,0x00,0x3F,0x00,0x3F,0x20,0x00,//M 45
	
	0x08,0xF8,0x30,0xC0,0x00,0x08,0xF8,0x08,
	0x20,0x3F,0x20,0x00,0x07,0x18,0x3F,0x00,//N 46
	
	0xE0,0x10,0x08,0x08,0x08,0x10,0xE0,0x00,
	0x0F,0x10,0x20,0x20,0x20,0x10,0x0F,0x00,//O 47
	
	0x08,0xF8,0x08,0x08,0x08,0x08,0xF0,0x00,
	0x20,0x3F,0x21,0x01,0x01,0x01,0x00,0x00,//P 48
	
	0xE0,0x10,0x08,0x08,0x08,0x10,0xE0,0x00,
	0x0F,0x18,0x24,0x24,0x38,0x50,0x4F,0x00,//Q 49
	
	0x08,0xF8,0x88,0x88,0x88,0x88,0x70,0x00,
	0x20,0x3F,0x20,0x00,0x03,0x0C,0x30,0x20,//R 50
	
	0x00,0x70,0x88,0x08,0x08,0x08,0x38,0x00,
	0x00,0x38,0x20,0x21,0x21,0x22,0x1C,0x00,//S 51
	
	0x18,0x08,0x08,0xF8,0x08,0x08,0x18,0x00,
	0x00,0x00,0x20,0x3F,0x20,0x00,0x00,0x00,//T 52
	
	0x08,0xF8,0x08,0x00,0x00,0x08,0xF8,0x08,
	0x00,0x1F,0x20,0x20,0x20,0x20,0x1F,0x00,//U 53
	
	0x08,0x78,0x88,0x00,0x00,0xC8,0x38,0x08,
	0x00,0x00,0x07,0x38,0x0E,0x01,0x00,0x00,//V 54
	
	0xF8,0x08,0x00,0xF8,0x00,0x08,0xF8,0x00,
	0x03,0x3C,0x07,0x00,0x07,0x3C,0x03,0x00,//W 55
	
	0x08,0x18,0x68,0x80,0x80,0x68,0x18,0x08,
	0x20,0x30,0x2C,0x03,0x03,0x2C,0x30,0x20,//X 56
	
	0x08,0x38,0xC8,0x00,0xC8,0x38,0x08,0x00,
	0x00,0x00,0x20,0x3F,0x20,0x00,0x00,0x00,//Y 57
	
	0x10,0x08,0x08,0x08,0xC8,0x38,0x08,0x00,
	0x20,0x38,0x26,0x21,0x20,0x20,0x18,0x00,//Z 58
	
	0x00,0x00,0x00,0xFE,0x02,0x02,0x02,0x00,
	0x00,0x00,0x00,0x7F,0x40,0x40,0x40,0x00,//[ 59
	
	0x00,0x0C,0x30,0xC0,0x00,0x00,0x00,0x00,
	0x00,0x00,0x00,0x01,0x06,0x38,0xC0,0x00,//\ 60
	
	0x00,0x02,0x02,0x02,0xFE,0x00,0x00,0x00,
	0x00,0x40,0x40,0x40,0x7F,0x00,0x00,0x00,//] 61
	
	0x00,0x00,0x04,0x02,0x02,0x02,0x04,0x00,
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//^ 62
	
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
	0x80,0x80,0x80,0x80,0x80,0x80,0x80,0x80,//_ 63
	
	0x00,0x02,0x02,0x04,0x00,0x00,0x00,0x00,
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//` 64
	
	0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,
	0x00,0x19,0x24,0x22,0x22,0x22,0x3F,0x20,//a 65
	
	0x08,0xF8,0x00,0x80,0x80,0x00,0x00,0x00,
	0x00,0x3F,0x11,0x20,0x20,0x11,0x0E,0x00,//b 66
	
	0x00,0x00,0x00,0x80,0x80,0x80,0x00,0x00,
	0x00,0x0E,0x11,0x20,0x20,0x20,0x11,0x00,//c 67
	
	0x00,0x00,0x00,0x80,0x80,0x88,0xF8,0x00,
	0x00,0x0E,0x11,0x20,0x20,0x10,0x3F,0x20,//d 68
	
	0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,
	0x00,0x1F,0x22,0x22,0x22,0x22,0x13,0x00,//e 69
	
	0x00,0x80,0x80,0xF0,0x88,0x88,0x88,0x18,
	0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,//f 70
	
	0x00,0x00,0x80,0x80,0x80,0x80,0x80,0x00,
	0x00,0x6B,0x94,0x94,0x94,0x93,0x60,0x00,//g 71
	
	0x08,0xF8,0x00,0x80,0x80,0x80,0x00,0x00,
	0x20,0x3F,0x21,0x00,0x00,0x20,0x3F,0x20,//h 72
	
	0x00,0x80,0x98,0x98,0x00,0x00,0x00,0x00,
	0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,//i 73
	
	0x00,0x00,0x00,0x80,0x98,0x98,0x00,0x00,
	0x00,0xC0,0x80,0x80,0x80,0x7F,0x00,0x00,//j 74
	
	0x08,0xF8,0x00,0x00,0x80,0x80,0x80,0x00,
	0x20,0x3F,0x24,0x02,0x2D,0x30,0x20,0x00,//k 75
	
	0x00,0x08,0x08,0xF8,0x00,0x00,0x00,0x00,
	0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,//l 76
	
	0x80,0x80,0x80,0x80,0x80,0x80,0x80,0x00,
	0x20,0x3F,0x20,0x00,0x3F,0x20,0x00,0x3F,//m 77
	
	0x80,0x80,0x00,0x80,0x80,0x80,0x00,0x00,
	0x20,0x3F,0x21,0x00,0x00,0x20,0x3F,0x20,//n 78
	
	0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,
	0x00,0x1F,0x20,0x20,0x20,0x20,0x1F,0x00,//o 79
	
	0x80,0x80,0x00,0x80,0x80,0x00,0x00,0x00,
	0x80,0xFF,0xA1,0x20,0x20,0x11,0x0E,0x00,//p 80
	
	0x00,0x00,0x00,0x80,0x80,0x80,0x80,0x00,
	0x00,0x0E,0x11,0x20,0x20,0xA0,0xFF,0x80,//q 81
	
	0x80,0x80,0x80,0x00,0x80,0x80,0x80,0x00,
	0x20,0x20,0x3F,0x21,0x20,0x00,0x01,0x00,//r 82
	
	0x00,0x00,0x80,0x80,0x80,0x80,0x80,0x00,
	0x00,0x33,0x24,0x24,0x24,0x24,0x19,0x00,//s 83
	
	0x00,0x80,0x80,0xE0,0x80,0x80,0x00,0x00,
	0x00,0x00,0x00,0x1F,0x20,0x20,0x00,0x00,//t 84
	
	0x80,0x80,0x00,0x00,0x00,0x80,0x80,0x00,
	0x00,0x1F,0x20,0x20,0x20,0x10,0x3F,0x20,//u 85
	
	0x80,0x80,0x80,0x00,0x00,0x80,0x80,0x80,
	0x00,0x01,0x0E,0x30,0x08,0x06,0x01,0x00,//v 86
	
	0x80,0x80,0x00,0x80,0x00,0x80,0x80,0x80,
	0x0F,0x30,0x0C,0x03,0x0C,0x30,0x0F,0x00,//w 87
	
	0x00,0x80,0x80,0x00,0x80,0x80,0x80,0x00,
	0x00,0x20,0x31,0x2E,0x0E,0x31,0x20,0x00,//x 88
	
	0x80,0x80,0x80,0x00,0x00,0x80,0x80,0x80,
	0x80,0x81,0x8E,0x70,0x18,0x06,0x01,0x00,//y 89
	
	0x00,0x80,0x80,0x80,0x80,0x80,0x80,0x00,
	0x00,0x21,0x30,0x2C,0x22,0x21,0x30,0x00,//z 90
	
	0x00,0x00,0x00,0x00,0x80,0x7C,0x02,0x02,
	0x00,0x00,0x00,0x00,0x00,0x3F,0x40,0x40,//{ 91
	
	0x00,0x00,0x00,0x00,0xFF,0x00,0x00,0x00,
	0x00,0x00,0x00,0x00,0xFF,0x00,0x00,0x00,//| 92
	
	0x00,0x02,0x02,0x7C,0x80,0x00,0x00,0x00,
	0x00,0x40,0x40,0x3F,0x00,0x00,0x00,0x00,//} 93
	
	0x00,0x06,0x01,0x01,0x02,0x02,0x04,0x04,
	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//~ 94
};

#endif

上图为OLED_Font.h文件，这里面就是OLED显示英文的字库，这是一个数组，这里面决定了，每一个字符应该显示在哪些像素点，这个数组非常的长，并且是不需要更改的。

所以在开头定义变量时，就可以加一个const，把它定义在Flash里面，这样就可以节省SRAM空间，这里如果const去掉了，程序功能不会有任何影响，但是SRAM里面会有和这个数组一样大的空间被浪费掉了，如果数组很小，影响就不大，如果数组很大，就要考虑一下SRAM是不是消耗的起了。

所以如果你有一个很大的查找表或者字库，最好加一个const。

实现代码

#include "stm32f10x.h"                  // Device header
#include "Delay.h"
#include "OLED.h"
#include "MyDMA.h"

uint8_t DataA[] = {0x01, 0x02, 0x03, 0x04};				//定义测试数组DataA，为数据源
uint8_t DataB[] = {0, 0, 0, 0};							//定义测试数组DataB，为数据目的地

int main(void)
{
	/*模块初始化*/
	OLED_Init();				//OLED初始化
	
	MyDMA_Init((uint32_t)DataA, (uint32_t)DataB, 4);	//DMA初始化，把源数组和目的数组的地址传入
	
	/*显示静态字符串*/
	OLED_ShowString(1, 1, "DataA");
	OLED_ShowString(3, 1, "DataB");
	
	/*显示数组的首地址*/
	OLED_ShowHexNum(1, 8, (uint32_t)DataA, 8);
	OLED_ShowHexNum(3, 8, (uint32_t)DataB, 8);
		
	
	}
}