使用74HC595来驱动LED数码管

前面讲过使用74LS47来驱动LED数码管，目的就是减少单片机IO引脚的使用量。如果单片机直接驱动LED数码管，每个数码管至少需要7个IO 引脚，如果使用74LS47，那么只需要4个引脚。如果要驱动多个数码管，要么引脚数量倍增，要么采用高频刷新的方式（每增加一位数码管，需要多占用一个引脚，并且数码管可能会有闪烁的现象）。今天介绍的74HC595，可以将引脚数量降低为3个，并且可以串行驱动任意多个数码管，无需再增加IO引脚数量，并且，LED数码管是没有任何闪烁的，效果非常好。

下面是74HC595的物理引脚定义和逻辑引脚标识：

Arduino的代码库中内置了ShiftOut方法，可以很方便的应用于74HC595。在这个示例中，我们使用一个74HC595驱动一个LED数码管，单片机采用Arduino UNO。

电路连接要点如下：

LED数码管（5161AS）的1,2,4,5,6,7,9,10引脚分别连接74HC595的Q0-Q7。

LED数码管的3引脚串接一个200欧的电阻然后接地。

74HC595的OE、GND接地，VCC、MR接电源正极。

74HC595的ST_CP接Arduino的3脚，SH_CP接Arduino的4脚，DS接Arduino的2脚。

我是在面包板上做测试的，很方便，实际连接图如下，其实啥也看不清，大家照着上述的连接方式连即可：

Arduino程序代码如下：

/*
 * Shift Register Example
 * Turning on the outputs of a 74HC595 using an array Hardware:
 * 74HC595 shift register
 * LEDs attached to each of the outputs of the shift register
 */
//Pin connected to ST_CP of 74HC595
int latchPin = 3;
//Pin connected to SH_CP of 74HC595
int clockPin = 4;
////Pin connected to DS of 74HC595
int dataPin = 2;
//holders for infromation you're going to pass to shifting function
byte data;
byte dataArray[10];
void setup() {
  //set pins to output because they are addressed in the main loop
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  //Binary notation as comment
  dataArray[0] = 0xEE;
  dataArray[1] = 0x82;
  dataArray[2] = 0xCD;
  dataArray[3] = 0x6D;
  dataArray[4] = 0x2B;
  dataArray[5] = 0x67;
  dataArray[6] = 0xE7;
  dataArray[7] = 0x2E;
  dataArray[8] = 0xEF;
  dataArray[9] = 0x6F;
}
void loop() {
  for (int j = 0; j < 10; j++) {
    //load the light sequence you want from array
    data = dataArray[j];
    //ground latchPin and hold low for as long as you are transmitting
    digitalWrite(latchPin, 0);
    //move 'em out
    shiftOut(dataPin, clockPin, LSBFIRST ,data);
    //return the latch pin high to signal chip that it
    //no longer needs to listen for information
    digitalWrite(latchPin, 1);
    delay(300);
  }
}

* Shift Register Example

* Turning on the outputs of a 74HC595 using an array Hardware:

* 74HC595 shift register

* LEDs attached to each of the outputs of the shift register

//Pin connected to ST_CP of 74HC595

int latchPin = 3;

//Pin connected to SH_CP of 74HC595

int clockPin = 4;

////Pin connected to DS of 74HC595

int dataPin = 2;

//holders for infromation you're going to pass to shifting function

byte data;

byte dataArray[10];

void setup() {

//set pins to output because they are addressed in the main loop

pinMode(latchPin, OUTPUT);

pinMode(clockPin, OUTPUT);

pinMode(dataPin, OUTPUT);

//Binary notation as comment

dataArray[0] = 0xEE;

dataArray[1] = 0x82;

dataArray[2] = 0xCD;

dataArray[3] = 0x6D;

dataArray[4] = 0x2B;

dataArray[5] = 0x67;

dataArray[6] = 0xE7;

dataArray[7] = 0x2E;

dataArray[8] = 0xEF;

dataArray[9] = 0x6F;

}

void loop() {

for (int j = 0; j < 10; j++) {

//load the light sequence you want from array

data = dataArray[j];

//ground latchPin and hold low for as long as you are transmitting

digitalWrite(latchPin, 0);

//move 'em out

shiftOut(dataPin, clockPin, LSBFIRST ,data);

//return the latch pin high to signal chip that it

//no longer needs to listen for information

digitalWrite(latchPin, 1);

delay(300);

}

代码运行的效果，就是LED数码管从0到9循环显示。

本次试验参考了74HC595的数据手册和Arduino的官方文档：

http://www.arduino.cc/en/Tutorial/ShiftOut

http://www.nxp.com/documents/data_sheet/74HC_HCT595.pdf

大家可以自行研究，尝试驱动多个LED数码管。

使用74HC595来驱动LED数码管

Published by

Meng Guang