//---------------------------------------
//AT24C04 EEPROM Programming via Arduino. 寫入字符串，讀取字符串
//---------------------------------------
#include <Wire.h>
//先定義待讀取的EEPROM地址
#define EEPROM1_I2C_address 0x50


void setup()
{                                                                     
  Serial.begin(9600);
  Wire.begin();

  char word[] = "test$hello world$";       //這個地方放置待寫入的字串

  char message1[100];     //宣告50個字的字符串

  writeStringToEEPROM(word);   //呼叫自製函數寫字串到EEPROM

  Serial.println("EEPROM 3: ");
  for(int i=0; i<=100; i++)       //最多讀取前200個字
  {
    
    char asciiChar = readFromEEPROM(EEPROM1_I2C_address, i);     //讀到的本身是數字，換成字元
    message1[i]=asciiChar;    //把讀到的字存到字符串1

  }  

String myString = message1;
int first_position = myString.indexOf("$");
int sec_position = myString.indexOf("$",first_position+1);
  
Serial.println(myString.substring(0, first_position));
Serial.println(myString.substring(first_position+1, sec_position));

}

void loop() {}

void writeStringToEEPROM(const char* str) {       //寫一串字到EEPROM中，位置0開始
  int len = strlen(str);
  for (int i = 0; i < len; i++) {
    writeToEEPROM(EEPROM1_I2C_address, i, str[i]);
  }

  writeToEEPROM(EEPROM1_I2C_address, len, '$');  // 寫入字符串結束符$
}


void writeToEEPROM(byte EEPROMAddress, byte dataAddress, byte dataValue)
{
  Wire.beginTransmission(EEPROMAddress);
  Wire.write(dataAddress);
  Wire.write(dataValue);
  Wire.endTransmission();
  delay(5);
}

byte readFromEEPROM(byte EEPROMAddress, byte dataAddress)
{
  Wire.beginTransmission(EEPROMAddress);
  Wire.write(dataAddress);
  Wire.endTransmission();
  delay(5);
  Wire.requestFrom(EEPROMAddress, 1);
  if(Wire.available()) return Wire.read();
}