ESP8266 Community Forum

Posted: **Tue Oct 11, 2016 4:58 am**

When I write to eeprom with the following code:

char test[8]="TESTi10";
void setup(){
   EEPROM.begin(20);                              
  for(int cc=0 ;cc<9;cc++){
    int value = test[cc]-'0'; //convert char to int
    EEPROM.put(cc,value);
    EEPROM.end();
    delay(20);
    Serial.println(value);
    delay(500);
  }
}

I get this in terminal(not bad):

Code: Select all

But when I read the stored data with the following code:

Code: Select all

void loop(){
EEPROM.begin(20);
  for(int cd=0;cd<9;cd++){
    EEPROM.get(cd,raw[cd]);
   
  }
  EEPROM.commit();
    EEPROM.end();
  for(int cd=0;cd<9;cd++){
    Serial.println(raw[cd]);
  }
   
}

I get this in terminal:

Code: Select all

as you can see only the first character saved on eeprom and others are rubish!
WHY ?? :cry:

Posted: **Wed Oct 12, 2016 9:52 am**

Your above code doesn't show up how the "raw" array is declared.
The EEPROM put/get methods are templated, so if you put chars and read them back into integers, it will be distorded since chars and integers are not the same size.
If you only wish to deal with chars, use read/write methods instead.

Posted: **Wed Oct 12, 2016 12:35 pm**

Thank you martinayotte.
With following code I can write once and read many times.
But when I turn off module and turn it on again and press read button it shows me this:

Code: Select all#$9ےےےےے

Code: Select all

void setup(){
EEPROM.begin(512);
}

void loop(){
  if (digitalRead(writeBtn)==0) {             
   delay(1000);
   if (digitalRead(WriteBtn)==0) {
  //write to eeprom
  String qsid="Global";
  int charLength=qsid.length();
  
  Serial.println("writing eeprom:");
          for (int i = 0; i < qsid.length(); ++i)
            {
              EEPROM.write(i, qsid[i]);
              Serial.print("Wrote: ");
              Serial.println(qsid[i]); 
            }

   }
  }

  if (digitalRead(readBtn)==0) {             //delete previous saved SSID and password value
   delay(1000);
   if (digitalRead(readBtn)==0) {
//read to eeprom
  Serial.println("Reading EEPROM:");
  String esid;
  for (int i = 0; i < 15; ++i)
    {
      esid += char(EEPROM.read(i));
    }
    //esid.trim();
    Serial.println(esid.length());
  
  Serial.println(esid);
  Serial.println("Reading EEPROM pass");
}
}
}

Can you please tell me what is wrong in my code?
Thank you in advance

Posted: **Fri Oct 14, 2016 2:43 pm**

Actually, all your write() are cached in RAM.
To be written to real EEPROM emulated in Flash, you need to do a EEPROM.commit() when you finished your write(), it will then be persisted.

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