2020年03月05日 | 51单片机-指针方法-串口实例

1. 指针

变量a的指针=变量a的地址

再定义一个变量p，来存放a的地址(指针)，p就是指针变量，简称指针

1.1 指针声明的两种方式

//直接初始化赋值

unsigned char a;

unsigned char *p = &a;

//定义后再进行赋值

unsigned char a;

unsigned char *p;

P = &a;

1.2 两个重要区别（P194）

第指针变量p与普通变量a的区别：

a可直接赋值，p要赋地址

定义指针变量*p和取值运算*p的区别

*的三种用法：

num = a * b; //乘号

unsigned char *p; //定义指针变量

num = *p; //取值运算，取p指向的值，赋值给num

1.3 指针流水灯

写流水灯的方法汇总：

软件延时，定时器

算法移位，移位函数，指针

#include

unsigned char T0RH,T0RL;

void ConfigTimer0(unsigned char ms);

void main(void)

{

ConfigTimer0(1);

while(1){}

}

void ConfigTimer0(unsigned char ms)

{

unsigned long tmp;

tmp = 11059200 / 12;

tmp = tmp * ms / 1000;

tmp = 65536 - tmp;

tmp += 6;

T0RH = (unsigned char)(tmp>>8);

T0RL = (unsigned char)tmp;

TH0 = T0RH;

TL0 = T0RL;

TMOD &= 0xF0;

TMOD |= 0x01;

EA = 1;

ET0 = 1;

TF0 = 0;

TR0 = 1;

}

void LedFlow(void)

{

static unsigned char buff = 0x01;

static unsigned char *p = &buff;

P1 = ~buff;

*p <<= 1;

if(0==buff)

{

buff = 0x01;

}

}

void InterruptTimer0(void) interrupt 1

{

static unsigned int tmr1s = 0;

TH0 = T0RH;

TL0 = T0RL;

tmr1s++;

if(tmr1s>=1000)

{

tmr1s = 0;

LedFlow();

}

}

2. 数组的指针

2.1 数组指针的声明

unsigned char num[10] = 

{

0,1,2,3,4,5,6,7,8,9

};

unsigned char *p = &num[0];

2.2 指针本身的运算（P197）

比较运算

两个指针需要指向，有同种数据类型的对象。

指针和整数的加减

两个指针相减

2.3 数组指针和sizeof()的用法实例

上位机发送命令，下位机回发对应数组值

#include

unsigned char table1[1] = {1};

unsigned char table2[2] = {1,2};

unsigned char table3[4] = {1,2,3,4};

unsigned char table4[8] = {1,2,3,4,5,6,7,8};

bit UARTArrived = 0;

unsigned char UARTNum;

unsigned char *UARTTable;

unsigned char TableCnt;

void ConfigUART(unsigned long baud);

void main(void)

{

ConfigUART(9600);

while(1)

{

if(UARTArrived)

{

UARTArrived = 0;

switch(UARTNum)

{

case 1 : UARTTable = &table1; TableCnt = sizeof(table1); TI = 1; break;

case 2 : UARTTable = &table2; TableCnt = sizeof(table2); TI = 1; break;

case 3 : UARTTable = &table3; TableCnt = sizeof(table3); TI = 1; break;

case 4 : UARTTable = &table4; TableCnt = sizeof(table4); TI = 1; break;

default : break;

}

}

}

}

void ConfigUART(unsigned long baud)

{

TH1 = 256 - (11059200/12/32) / baud;

TL1 = TH1;

SCON = 0x50;

TMOD &= 0x0F;

TMOD |= 0x20;

EA = 1;

ET1 = 0;

ES = 1;

TF1 = 0;

TR1 = 1;

}

void InterruptUART(void) interrupt 4

{

if(RI)

{

RI = 0;

UARTNum = SBUF;

UARTArrived = 1;

}

if(TI)

{

TI = 0;

if(TableCnt>0)

{

SBUF = *UARTTable++;

TableCnt--;

}

}

}

3.字符数组&字符指针

3.1 常量

常量：整形常量，浮点型常量，字符型常量，字符串常量

3.2 直接常量

就是一个值

3.3 符号常量

符号常量声明：

const声明

const 类型 符号常量名字 = 常量值;

const unsigned long BAUD = 9600;

预处理命令#define

#define 符号常量名字 常量值

#define BAUD 9600

3.4 区别实例

区别字符串，字符数组，常量数组

上位机发送命令，下位机回发对应数组值

#include

const unsigned long BAUD = 9600;

unsigned char table1[] = {"1-Hello!rn"};

unsigned char table2[] = {'2','-','H','e','l','l','o','!','r','n'};

unsigned char table3[] = {51,45,72,101,108,108,111,33,13,10};

unsigned char table4[] = {"4-Hello!rn"};

bit arrived = 0;

unsigned char index;

unsigned char cnt;

unsigned char *p;

void ConfigUART(void);

void main(void)

{

ConfigUART();

while(1)

{

if(arrived)

{

arrived = 0;

switch(index)

{

case 1 : p = &table1; cnt = sizeof(table1); TI = 1; break;

case 2 : p = &table2; cnt = sizeof(table2); TI = 1; break;

case 3 : p = &table3; cnt = sizeof(table3); TI = 1; break;

case 4 : p = &table4; cnt = sizeof(table4)-1; TI = 1; break;

default : break;

}

}

}

}

void ConfigUART(void)

{

TH1 = 256 - (11059200/12/32) / BAUD;

TL1 = TH1;

SCON = 0x50;

TMOD &= 0x0F;

TMOD |= 0x20;

EA = 1;

ET1 = 0;

ES = 1;

TF1 = 0;

TR1 = 1;

}

void InterruptUART(void) interrupt 4

{

if(RI)

{

RI = 0;

index = SBUF;

arrived = 1;

}

if(TI)

{

TI = 0;

if(cnt>0)

{

SBUF = *p++;

cnt--;

}

}

}