3个普通IO识别22个按键试验

电路接线就是P1.2,P1.3,P1.4接键盘，P1.0接显示器。0 o8 ^" k* ], [* Y: |* _2 G
/*==================================================================*
* 3个IO接识别22键测试程序 * / p6 s0 V; S/ @9 F: I
* ------------------------------------------------ *
* MCU: AT89C2051 *
* OSC: 12M cysytel *
* 程序设计:Cowboy *
* 程序版本:V1.0 *
*==================================================================*/ , M1 o+ w V1 o1 U( |) G6 v) Q

#include <reg52.h> % N5 f. L4 |( M! ?/ v' I4 ^
( g9 H. q |" \4 D4 M% F: | r
//================== IO口线连接 ==================
sbit Bus = P1^0; % o A( n' D" e& o
sbit IO_a = P1^4;
sbit IO_b = P1^3;
sbit IO_c = P1^2; ; b5 g' t1 _' ]4 J4 q8 T8 Q( t
. ?+ q: G* A! q9 E# E, T
//================== 变量声明 ==================== 6 l P1 J) W8 `' j0 h- y5 Z
unsigned char Disp_buf[3]; / p& b' V& Z4 c
unsigned char Dig;
unsigned char Key_count; ! e5 I" E7 @" c% w
unsigned char bdata Key_state; 2 [) a# L9 F* [) \
sbit KB0 = Key_state^0; ; E2 _, A7 Y0 [4 m% M5 s
sbit KB1 = Key_state^1; - Z }0 k: T. n' @( ]+ ~9 P7 _
sbit KB2 = Key_state^2;
sbit KB3 = Key_state^3; ; t- t; v( v6 H. V
sbit KB4 = Key_state^4;
sbit KB5 = Key_state^5;

//================== 表格数据 ==================== m: t ]/ D4 i
code unsigned char LED_font[24]= 9 `. t; l. F( s
{ ) q4 w( F6 v* M% m
0x84,0x9f,0xa2,0x8a,0x99,0xc8,0xc0,0x9e,0x80, //012345678 % k. u, E9 ?1 _9 E! D
0x88,0x90,0xc1,0xe4,0x83,0xe0,0xf0,0xff,0xfb, //9abcdef - # x4 j# c8 i. Q Q8 |$ v& z
};

code unsigned char Key_tab[64]= //键码映射表 9 H: L( c1 c" ^0 d3 f. B
{// 0 1 2 3 4 5 6 7 8 9
22, 0, 2, 0, 0, 0, 0, 0, 4, 0, //0 2 `+ Z3 l9 ]- T7 E2 L' u0 q5 N7 d
0, 0, 0, 0, 0,18, 0, 0, 0, 0, //1X
0, 0, 0, 0, 0, 0, 3,14, 0, 0, //2X
20,10, 6, 0, 0, 0, 0, 0, 1,19, //3X ! w% \3 y6 [: \9 I u/ k
0, 5, 0, 0, 0,15, 0,11, 0, 0, //4X & A1 G" r: a9 e" w1 N
0,17, 0, 0,13, 8, 0,21, 0, 9, //5X ; }5 d, A/ v, f; `& }3 a& Y& A+ J; `1 p8 O
16,12, 7, 0 //6X
};

//=============== 检测按键 ================= 7 _4 \! q5 C/ o! _9 l& |7 W
void Key_scan()
{ , q% P8 i D+ M0 Q, a
unsigned char i; 0 h6 @; H2 K2 @8 x; H, S" h; }8 L
Key_count --; //扫描次序 " s4 \$ l2 q; d5 {/ H- y
Key_count &= 3;
switch (Key_count) //按次序处理
{ % u, k/ u1 e+ m# R
case 2: //第一轮扫描 4 D" n3 _' D/ ^# s5 k" G7 J
KB0 = IO_b; p* n$ N" g: W
KB1 = IO_c;
IO_a = 1; ) I# M, O$ S x8 ?3 D+ }3 @5 b1 |+ X
IO_b = 0; 7 Z7 [- @3 [7 d6 T6 \5 A& s
break; 3 o* l2 {- n5 B% U+ U/ r9 W

case 1: //每二轮扫描
KB2 = IO_c; ) X1 n* o% j6 |' p
KB3 = IO_a;
IO_b = 1;
IO_c = 0;
break;

case 0: //每三轮扫描
KB4 = IO_a; ! s( v$ _0 h+ K2 r \
KB5 = IO_b;
IO_c = 1; B, i9 y6 o" d3 n( M; D8 h* ?
break; $ t1 M8 [2 c- w3 o# y
4 F% }5 C* P8 S/ r- ?# F" f- u
default: //每四轮扫描 $ }9 p! U* W0 I
if (!IO_a) KB0 = 0; 7 ^: D/ ?$ [ m3 t% V
if (!IO_b) KB2 = 0;
if (!IO_c) KB4 = 0; 8 c7 I2 _2 @" S* z6 j
IO_a = 0;

//======更新显示缓冲区=======
i = Key_tab[Key_state]; / {7 y' L- t% t9 G4 B
if (i == 0)
{ % H+ i1 d# y% k1 k/ e" o
Disp_buf[2] = 0x11; //显示三横
Disp_buf[1] = 0x11;
Disp_buf[0] = 0x11;
} 0 O- |% S. ]2 p
else 0 p. M4 [4 r) w
{ $ {. m4 |1 o7 v9 t* W% z
Disp_buf[2] = 0x0c; //字符"C" 9 a8 ~/ o8 `3 h% j# C
Disp_buf[1] = i / 10; //键码十位
Disp_buf[0] = B;于 //键码个位 # X% X) v3 T' T4 V! c$ }/ _
} . u x- @4 q5 ~ [& T
Key_state = 0; , a3 ]9 `, b, R4 B5 M. E. W
} 6 B( I6 m: h0 Z. W" Y$ ]/ N
} 5 O6 }/ |7 c) M9 R S
! C) T# m- S& s
4 \% ]) k& o1 N; A
/*===================================================================
ONE WIRE 显示总线驱动程序
===================================================================*/

//=============== 发送一位 ================= * h9 y$ f( z4 t9 E5 U
void Send_bit(bit Dat)
{ ) h+ T, j$ b2 o5 z) o/ M
unsigned char i = 3;
if (!Dat) Bus = 0;
else
{ 6 N% k" S1 |% s) E5 V( L# _0 Q
Bus = 0;
Bus = 1;
}
while(--i); //延时8us
Bus = 1;
} ; I( x2 j: D9 l$ _! j+ W

//=============== 总线驱动 =================
void Bus_drive()
{
unsigned char i = 0; 3 {6 V/ ~: M" q6 G
unsigned char Sdat; 6 p8 Q. T) V9 s4 j$ l
Send_bit(1); //Bit6消隐 1 @, {9 l) `- M# K3 j G$ C; _8 I
do Bus = 1; while(--i); //延时768us $ \; w+ N# S9 v
do Bus = 0; while(--i); //延时768us
Bus = 1; 9 n E0 ]. w% [; Y
Sdat = LED_font[Disp_buf[Dig++]]; //获取显示数据 / ?9 I( e/ E$ h0 @. L/ o* h
Send_bit(Sdat & 0x01); //发送位0 + }/ F- ]5 l, q" @8 W) `& \
Send_bit(Sdat & 0x02); //发送位1 + k0 L& B* o5 b3 X/ D- t9 _. n
Send_bit(Sdat & 0x04); //发送位2 ( E% [' \! S* ]# U) q
Send_bit(Sdat & 0x08); //发送位3 4 O" O, x1 j$ u9 |
Send_bit(Sdat & 0x10); //发送位4
Send_bit(Sdat & 0x20); //发送位5 ) _; V* v! N @
Send_bit(Dig & 0x01); //发送位选1
Send_bit(Dig & 0x02); //发送位选2
while(--i); //延时512us
Send_bit(Sdat & 0x40); //发送位6
for (i = 7;i> 0;i--) Send_bit(1); //位6移至Dout ; Q" q9 G1 w- s4 J9 f6 B
if (Dig == 3) Dig = 0;
}

/*===================================================================
延时 5ms 程序
===================================================================*/
void Delay_5ms() + o# F+ X% g/ g; B0 E3 x5 N: H
{ 4 ~9 }! } y) f7 J
while(!TF1); / d# H W' w- u
TF1 = 0; ' N; x: b. y! R2 @$ m
TH1 = (- 5000) / 256;
TL1 = (- 5000) % 256; 8 a3 `. y! p& v) [
} 4 i3 o0 Y0 L/ d! G7 I* L

/*=================================================================== 0 v/ V5 n+ c' W3 ~
主程序 - @ `2 ?2 i* X/ B* T7 v3 ]( ~% }
===================================================================*/ 6 o& {# T, E( M# r2 d+ t: i
void main()
{ 8 D& P; p8 Q3 J% u: @6 x
TMOD = 0x10; //定时器1，16位模式 , Z2 | F. H# R* m. |
TCON = 0xc0; //TR1=1;TF1=1;
while(1) //主循环 ; a/ D- \9 f; p/ V! I
{
Bus_drive(); //显示总线驱动
Key_scan(); //检测按键
Delay_5ms(); //延时5MS 1 }% H/ u7 u$ c: C2 t( v1 E. X
} . M* v* b( l) L; B
}
作为试验目的，没有接按键，只焊了个键盘框架，用镊子短路相应的节点来当按键。图中接二极管阵列的三根线是3个IO，单独的一根是地线。MCU发送串行数据给HC595驱动数码管作键码显示。
对于这种方式的按键识别方法,很多朋友担心编程会很复杂,其实仔细分析后也很简单.比如上面例子,其本的思路是依次把三个IO拉低,然后记录另外两个IO的状态,最后三个IO都不下拉,再记录一次,就可得出的结果.对于按下不同的按键,就有不同的结果.如果只扫18键,那么最后一次扫描可以省掉,即扫描三次即可.实际应用时5MS的扫描间隔可以用定时中断来实现,这样就只占用很少的MCU时间 .