Freenove Ultimate Starter Kit

191
Chapter 18 74HC595 & 7-segment display.
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Code
In this code, uses 74HC595 to control the 7-segment display. The usage of 74HC595 is generally the same to
last section. The content 74HC595 outputs is different. We need code character “0”- “F” one by one, and then
output them with 74HC595.
C Code 18.1.1 SevenSegmentDisplay
First observe the project result, and then analyze the code.
1. Use cd command to enter 18.1.1_SevenSegmentDisplay directory of C code.
cd ~/Freenove_Ultimate_Starter_Kit_for_Raspberry_Pi/Code/C_Code/18.1.1_SevenSegmentDisplay
2. Use following command to compile “SevenSegmentDisplay.c” and generate executable file
“SevenSegmentDisplay”.
gcc SevenSegmentDisplay.c -o SevenSegmentDisplay -lwiringPi
3. Then run the generated file “SevenSegmentDisplay”.
sudo ./SevenSegmentDisplay
After the program is executed, SevenSegmentDisplay starts to display the character “0”- “F” successively.
The following is the program code:
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#include <wiringPi.h>
#include <stdio.h>
#include <wiringShift.h>
#define dataPin 0 //DS Pin of 74HC595(Pin14)
#define latchPin 2 //ST_CP Pin of 74HC595(Pin12)
#define clockPin 3 //CH_CP Pin of 74HC595(Pin11)
//encoding for character 0-F of common anode SevenSegmentDisplay.
unsigned char
num[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90,0x88,0x83,0xc6,0xa1,0x86,0x8e};
void _shiftOut(int dPin,int cPin,int order,int val){
int i;
for(i = 0; i < 8; i++ ){
digitalWrite(cPin,LOW);
if(order == LSBFIRST){
digitalWrite(dPin,((0x01&(val>>i)) == 0x01) ? HIGH : LOW);
delayMicroseconds(10);
}
else {//if(order == MSBFIRST){
digitalWrite(dPin,((0x80&(val<<i)) == 0x80) ? HIGH : LOW);
delayMicroseconds(10);
}
digitalWrite(cPin,HIGH);
delayMicroseconds(10);
}
}