When you develop a project, it often needs to make IO expansion.The 74HC595 shifting register is a good choice. Following will introduce you that use two pieces 74HC595 to realize the display system of four digital LED(of course, can also realize 8 digital LED display) .It only uses three IO (PIN2,3, 5) of Arduino.
The picture to show the overall effect of the project.
Schematic diagram:
The wiring diagram:
How to make it?
First prepare the following components
1.DuPont line: 30PCS
- ICStation UNO development board ( Or Arduino UNO development board)
3.four digital LED display with the same anode.
- 20 PCS 20mm pin header
5.Bread board
6.2PCS 74HC595
7.USB Cable
4PCS 47? resistance
To build the circuit according to the schematic diagram
Because we only do testing, maybe it is not practical.If you want it to have practical use, you should weld it manually which will make the circuit more stable. When you build the circuit by hand the pin header is needed which will help you to change the DuPont line to jumper wires immediately.
Download Diagram:
Attachment: the program
/*
Designed by Icstation
Do you want to show your DIY and want to share your great idea with others?
Or you have many problems about electronics that need to be solved.
Our purpose is to help you to learn more about electronics.
This file is download from ICstation BBS
If you have any question, please visit our BBS:
http://www.icstation.com/forum/
Thank you !!!
*/
#define HC_DATA_H digitalWrite(data, HIGH) // data line output high
#define HC_DATA_L digitalWrite(data, LOW) //date line output low
#define HC_RCK_H digitalWrite(rck, HIGH) // rck output high
#define HC_RCK_L digitalWrite(rck, LOW) // rck output low
#define HC_SCK_H digitalWrite(sck, HIGH) // sck output high
#define HC_SCK_L digitalWrite(sck, LOW) // sck output low
unsigned char LED_BCD[16] ={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90,0x88,0x83,0xc6,0xa1,0x86,0x8e }; //common anode digital tube BCD code
//Define the pin
int data =2;
int rck =3;
int sck =5;
// the setup routine runs once when you press reset:
void setup() {
// initialize the digital pin as an output.
pinMode(data, OUTPUT);
pinMode(rck, OUTPUT);
pinMode(sck, OUTPUT);
pinMode(sclr, OUTPUT);
}
// the loop routine runs over and over again forever:
void loop() {
unsigned char dopp =0;
for( unsigned char i=0; i < 4; ++i)
{
if(i ==3) dopp =1;
else dopp =0;
HC_data_analyze(i,i,dopp); //Nixie Tube display
}
}
void HC_data_analyze(char LED_number,unsigned char LED_display,unsigned char LED_dp)
{
// data analyse
unsigned int HC_DISP = 0,HC_LEDCODE,HC_LEDCODE_temp=0;
if(LED_display > 15) LED_display = 0;
HC_LEDCODE = LED_BCD[LED_display] ; //get BCD code
for(unsigned char i=0; i < 8;++i)
{
HC_LEDCODE_temp <<=1;
if(HC_LEDCODE&0x01) HC_LEDCODE_temp |= 0x01;
HC_LEDCODE >>=1;
}
if(LED_dp) HC_LEDCODE_temp &= 0xfe;
HC_DISP = HC_LEDCODE_temp;
switch(LED_number)
{
case 0: HC_DISP |= 0x8000;break;
case 1: HC_DISP |= 0x4000;break;
case 2: HC_DISP |= 0x2000;break;
case 3: HC_DISP |= 0x1000;break;
}
write_74HC595(HC_DISP); //74HC595 shifting register data transfer
}
void write_74HC595( unsigned int data_a) //communication with 74HC595
{
char look =0;
HC_RCK_L; //latch open
HC_SCK_L;
for (;look < 16; ++look)
{
if(data_a&0x0001) {HC_DATA_H;}
else {HC_DATA_L;}
HC_SCK_H;
HC_SCK_L;
data_a >>= 1;
}
HC_RCK_H;
}