第8章 函数进阶与按键
按键物理特性导致存在前沿和后沿抖动存在，抖动时间大约再10ms，稳定闭合时间一般再100ms左右，做少也要40ms以上。
消抖方法：将按键动作过程的判定转化为对按键状态的判定。比如每2ms进入一次中断，连续的8次中断也就是16ms之内都是0，表明按键按下了。如果都是1表明按键没有按下动作。
电路图：
根据矩阵按键，按下某个按键，再数码管上显示对应的内容（0到F），代码如下：
#include<reg52.h>
sbit ADDR0 = P1^0;
sbit ADDR1 = P1^1;
sbit ADDR2 = P1^2;
sbit ADDR3 = P1^3;
sbit ENLED = P1^4;
sbit KEY_IN_1 = P2^4;
sbit KEY_IN_2 = P2^5;
sbit KEY_IN_3 = P2^6;
sbit KEY_IN_4 = P2^7;
sbit KEY_OUT_1 = P2^3;
sbit KEY_OUT_2 = P2^2;
sbit KEY_OUT_3 = P2^1;
sbit KEY_OUT_4 = P2^0;
unsigned char code LedChar[]={
0xC0, 0xF9, 0xA4, 0xB0, 0x99, 0x92, 0x82, 0xF8,
0x80, 0x90, 0x88, 0x83, 0xC6, 0xA1, 0x86, 0x8E
};
unsigned char KeySta[4][4] = { //保存着按键状态是按下还是抬起
{1,1,1,1},{1,1,1,1},{1,1,1,1},{1,1,1,1}
};
void main()
{
unsigned char i, j;
unsigned char backup [4][4] = { //存放上一次按键状态，每次按键发生变化需要更新
{1,1,1,1},{1,1,1,1},{1,1,1,1},{1,1,1,1}
};
EA = 1; //打开总中断
ENLED = 0; //使能38译码器
ADDR3 = 1;
ADDR2 = 0; //开启第一个数码管
ADDR1 = 0;
ADDR0 = 0;
TMOD = 0x01; //设置定时器0的模式1
TH0 = 0xFC; //赋初值，实现1ms定时
TL0 = 0x67;
ET0 = 1; //打开定时器0中断
TR0 = 1; //启动定时器0
P0 = LedChar[0]; //让数码管默认显示0
while(1)
{
for(i=0; i<4; i++)
{
for(j=0; j<4; j++)
{
if(backup[i][j] != KeySta[i][j])
{
if(backup[i][j] == 0)
{
P0 = LedChar[i*4+j];
}
backup[i][j] = KeySta[i][j];
}
}
}
}
}
//中断函数负责检测按键并更新按键状态
void InterruptTimer0() interrupt 1
{
static unsigned char keyout = 0;
unsigned char i = 0;
static unsigned char keybuf[4][4] = { //每1ms进入中断检测一bit按键状态存入矩阵对应按键中
{0xFF, 0xFF, 0xFF, 0xFF},
{0xFF, 0xFF, 0xFF, 0xFF},
{0xFF, 0xFF, 0xFF, 0xFF},
{0xFF, 0xFF, 0xFF, 0xFF}
};
TH0 = 0xFC;
TL0 = 0x67;
keybuf[keyout][0] = (keybuf[keyout][0] <<1) | KEY_IN_1;
keybuf[keyout][1] = (keybuf[keyout][1] <<1) | KEY_IN_2;
keybuf[keyout][2] = (keybuf[keyout][2] <<1) | KEY_IN_3;
keybuf[keyout][3] = (keybuf[keyout][3] <<1) | KEY_IN_4;
for(i=0; i<4; i++)
{
if((keybuf[keyout][i] & 0x0F) == 0x00)
{
KeySta[keyout][i] = 0;
}
else if((keybuf[keyout][i] & 0x0F) == 0x0F)
{
KeySta[keyout][i] = 1;
}
}
keyout++; //扫描下一行按键
keyout = keyout & 0x03;
switch(keyout)
{
case 0: KEY_OUT_4 = 1; KEY_OUT_1 = 0; break;
case 1: KEY_OUT_1 = 1; KEY_OUT_2 = 0; break;
case 2: KEY_OUT_2 = 1; KEY_OUT_3 = 0; break;
case 3: KEY_OUT_3 = 1; KEY_OUT_4 = 0; break;
default: break;
}
}简单加法器，代码如下：
#include<reg52.h>
sbit ADDR0 = P1^0;
sbit ADDR1 = P1^1;
sbit ADDR2 = P1^2;
sbit ADDR3 = P1^3;
sbit ENLED = P1^4;
sbit KEY_IN_1 = P2^4;
sbit KEY_IN_2 = P2^5;
sbit KEY_IN_3 = P2^6;
sbit KEY_IN_4 = P2^7;
sbit KEY_OUT_1 = P2^3;
sbit KEY_OUT_2 = P2^2;
sbit KEY_OUT_3 = P2^1;
sbit KEY_OUT_4 = P2^0;
unsigned char code LedChar[]={
0xC0, 0xF9, 0xA4, 0xB0, 0x99, 0x92, 0x82, 0xF8,
0x80, 0x90, 0x88, 0x83, 0xC6, 0xA1, 0x86, 0x8E
};
unsigned char KeySta[4][4] = {
{1,1,1,1},{1,1,1,1},{1,1,1,1},{1,1,1,1}
};
unsigned char LedBuff[6] = {
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
};
unsigned char code KeyCodeMap[4][4] = { //矩阵按键编号到标准键盘键码的映射表
{ 0x31, 0x32, 0x33, 0x26 }, //数字键1、数字键2、数字键3、向上键
{ 0x34, 0x35, 0x36, 0x25 }, //数字键4、数字键5、数字键6、向左键
{ 0x37, 0x38, 0x39, 0x28 }, //数字键7、数字键8、数字键9、向下键
{ 0x30, 0x1B, 0x0D, 0x27 } //数字键0、ESC键、 回车键、 向右键
};
void KeyDriver();
void main()
{
EA = 1; //使能总中断
ENLED = 0; //选择数码管进行显示
ADDR3 = 1;
TMOD = 0x01; //设置T0为模式1
TH0 = 0xFC; //为T0赋初值0xFC67，定时1ms
TL0 = 0x67;
ET0 = 1; //使能T0中断
TR0 = 1; //启动T0
LedBuff[0] = LedChar[0]; //上电显示0
while (1)
{
KeyDriver(); //调用按键驱动函数
}
}
void ShowNumber(unsigned long num)
{
signed char i;
unsigned char buf[6];
for(i=0; i<6; i++)
{
buf[i] = num % 10;
num = num / 10;
}
for(i=5; i>=1; i--)
{
if(buf[i] == 0)
{
LedBuff[i] = 0xFF;
}
else
break;
}
for(; i>=0; i--)
{
LedBuff[i] = LedChar[buf[i]];
}
}
void KeyAction(unsigned char keycode)
{
static unsigned long result = 0;
static unsigned long addend = 0;
if((keycode >= 0x30) &&(keycode <= 0x39))
{
addend = (addend *10) + (keycode - 0x30);
ShowNumber(addend);
}
else if(keycode == 0x26)
{
result += addend;
addend = 0;
ShowNumber(result);
}
else if(keycode == 0x0D)
{
result += addend;
addend = 0;
ShowNumber(result);
}
else if(keycode == 0x1B)
{
addend = 0;
result = 0;
ShowNumber(addend);
}
}
void KeyDriver()
{
unsigned char i, j;
static unsigned char backup [4][4] = {
{1,1,1,1},{1,1,1,1},{1,1,1,1},{1,1,1,1}
};
for(i=0; i<4; i++)
{
for(j=0; j<4; j++)
{
if(backup[i][j] != KeySta[i][j])
{
if(backup[i][j] == 0)
{
KeyAction(KeyCodeMap[i][j]);
}
backup[i][j] = KeySta[i][j];
}
}
}
}
/* 按键扫描函数，需在定时中断中调用，推荐调用间隔1ms */
void KeyScan()
{
unsigned char i;
static unsigned char keyout = 0; //矩阵按键扫描输出索引
static unsigned char keybuf[4][4] = { //矩阵按键扫描缓冲区
{0xFF, 0xFF, 0xFF, 0xFF}, {0xFF, 0xFF, 0xFF, 0xFF},
{0xFF, 0xFF, 0xFF, 0xFF}, {0xFF, 0xFF, 0xFF, 0xFF}
};
//将一行的4个按键值移入缓冲区
keybuf[keyout][0] = (keybuf[keyout][0] << 1) | KEY_IN_1;
keybuf[keyout][1] = (keybuf[keyout][1] << 1) | KEY_IN_2;
keybuf[keyout][2] = (keybuf[keyout][2] << 1) | KEY_IN_3;
keybuf[keyout][3] = (keybuf[keyout][3] << 1) | KEY_IN_4;
//消抖后更新按键状态
for (i=0; i<4; i++) //每行4个按键，所以循环4次
{
if ((keybuf[keyout][i] & 0x0F) == 0x00)
{ //连续4次扫描值为0，即4*4ms内都是按下状态时，可认为按键已稳定的按下
KeySta[keyout][i] = 0;
}
else if ((keybuf[keyout][i] & 0x0F) == 0x0F)
{ //连续4次扫描值为1，即4*4ms内都是弹起状态时，可认为按键已稳定的弹起
KeySta[keyout][i] = 1;
}
}
//执行下一次的扫描输出
keyout++; //输出索引递增
keyout = keyout & 0x03; //索引值加到4即归零
switch (keyout) //根据索引，释放当前输出引脚，拉低下次的输出引脚
{
case 0: KEY_OUT_4 = 1; KEY_OUT_1 = 0; break;
case 1: KEY_OUT_1 = 1; KEY_OUT_2 = 0; break;
case 2: KEY_OUT_2 = 1; KEY_OUT_3 = 0; break;
case 3: KEY_OUT_3 = 1; KEY_OUT_4 = 0; break;
default: break;
}
}
/* 数码管动态扫描刷新函数，需在定时中断中调用 */
void LedScan()
{
static unsigned char i = 0; //动态扫描的索引
P0 = 0xFF; //显示消隐
switch (i)
{
case 0: ADDR2=0; ADDR1=0; ADDR0=0; i++; P0=LedBuff[0]; break;
case 1: ADDR2=0; ADDR1=0; ADDR0=1; i++; P0=LedBuff[1]; break;
case 2: ADDR2=0; ADDR1=1; ADDR0=0; i++; P0=LedBuff[2]; break;
case 3: ADDR2=0; ADDR1=1; ADDR0=1; i++; P0=LedBuff[3]; break;
case 4: ADDR2=1; ADDR1=0; ADDR0=0; i++; P0=LedBuff[4]; break;
case 5: ADDR2=1; ADDR1=0; ADDR0=1; i=0; P0=LedBuff[5]; break;
default: break;
}
}
/* T0中断服务函数，用于数码管显示扫描与按键扫描 */
void InterruptTimer0() interrupt 1
{
TH0 = 0xFC;
TL0 = 0x67;
LedScan();
KeyScan();
}
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