LED 7 segment dusplay with 74HC595 and 8 digits

74HC595_ LED_7segm_8digits.cpp

#include "Arduino.h"


void display_start();
void display_value(const char* value);
int indexOf (const char* base, char ch, int startIndex);

void setup(){
    display_start();
}

void loop() {
    display_value("12345678");
}


//****************************************************************************************************************************************************
//                7 S E G M E N T   8 D I G I T S  74HC595  D I S P L A Y                                                                  *
//****************************************************************************************************************************************************

#define latchPin 22
#define dataPin 21
#define clockPin 17

const byte ARRAY_SIZE = 27;
byte segment_codes[ARRAY_SIZE];
String available_chars[ARRAY_SIZE];


void display_start() {

  segment_codes[ 0]=0b11000000; // 0
  segment_codes[ 1]=0b11111001; // 1
  segment_codes[ 2]=0b10100100; // 2
  segment_codes[ 3]=0b10110000; // 3
  segment_codes[ 4]=0b10011001; // 4
  segment_codes[ 5]=0b10010010; // 5
  segment_codes[ 6]=0b10000010; // 6
  segment_codes[ 7]=0b11111000; // 7
  segment_codes[ 8]=0b10000000; // 8
  segment_codes[ 9]=0b10010000; // 9
  segment_codes[10]=0b10001000; // a
  segment_codes[11]=0b10000011; // b
  segment_codes[12]=0b10100111; // c
  segment_codes[13]=0b10100001; // d
  segment_codes[14]=0b10000110; // e
  segment_codes[15]=0b10001110; // f
  segment_codes[16]=0b10001001; // H
  segment_codes[17]=0b11000111; // L
  segment_codes[18]=0b10001100; // P
  segment_codes[19]=0b10111111; // -
  segment_codes[20]=0b11110111; // _
  segment_codes[21]=0b11111111; // space
  segment_codes[22]=0b10110110; // unknown

  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);

}

int findIndexOfChar(char character){
    char s[24] = {"0123456789abcdefHLPS-_ "};
    int p =  indexOf(s, character, 0);
    if(p == -1) p = 22;
    return p;
}

void display_value(const char* value) {
    uint8_t j[8] = {3, 2, 1, 0, 7, 6, 5, 4};
    int     skip = 0;
    for(int i = 0; i < strlen(value); i++) {
        if(!((String)value[i]).equals(".")) {
            int indexOfCharToWrite = findIndexOfChar(value[j[i]]);
            if(indexOfCharToWrite > -1) {
                byte bitToWrite = 0;
                digitalWrite(latchPin, LOW);
                byte    code = segment_codes[indexOfCharToWrite];
                boolean skipNext = false;
                if(((String)value[i + 1]).equals(".")) {
                    bitWrite(code, 7, 0);
                    skipNext = true;
                }
                shiftOut(dataPin, clockPin, MSBFIRST, code);
                bitWrite(bitToWrite, i - skip, 1);
                shiftOut(dataPin, clockPin, LSBFIRST, bitToWrite);
                digitalWrite(latchPin, HIGH);
                if(skipNext) { skip++; }
            }
        }
    }
}

int indexOf (const char* base, char ch, int startIndex = 0) {
    const char *p = base;
    for (; startIndex > 0; startIndex--)
        if (*p++ == '\0') return -1;
    char *pos = strchr(p, ch);
    if (pos == nullptr) return -1;
    return pos - base;
}