How to read/write in the EEPROM?

Projects Programming
1

Hi:

Tried to follow some guidelines, I even copied and pasted a portion of code but when the values are read, they are not the same as should have been saved.

I need to save 6 values from around 1000 and 2000 (yes RC pulse values). I understand that values are saved as bytes, so I must divide by 256 for the highbyte and store the remain for the lowbyte.

This is the code I use to write:

void writeChannelSetting(uint8_t nIndex,uint16_t unSetting)
{
    EEPROM.write(nIndex*sizeof(uint16_t),lowByte(unSetting));
    EEPROM.write((nIndex*sizeof(uint16_t))+1,highByte(unSetting));
}

But the code that reads the values does this:

void readSettingsFromEEPROM()
{
  minPulseWidthThr = readChannelSetting(EEPROM_INDEX_minPulseWidthThr); (etc.)

It seems to be reading just one byte. Is it enough to have one index per value? If the value takes two bytes, shouldn't I read two indexed positions?

is there any working example storing and reading values greater than one byte?

2 
(etc.)

I can't believe that compiles.

3

it seems to be reading just one byte.

yes it does that is how it works for both read and write.
http://arduino.cc/en/Reference/EEPROM
If you want it to read or write more than one byte then you have to code it to do so using multiple EEPROM calls.

4

You have not posted the code for readChannelSetting(). We can only guess at what it is doing.

5

Yes, anyway I saw the error: he was reading just the first byte, though both (high andd low bytes were saved).

Now it works:

//  SAVE pulse width as two bytes
void writeChannelSetting(uint8_t nIndex,uint16_t unSetting)
{
    EEPROM.write(nIndex,highByte(unSetting));
    EEPROM.write(nIndex+1,lowByte(unSetting));
 }

//  READ BOTH BYTES AT INDEX nStart and nStart+1
uint16_t readChannelSetting(uint8_t nStart)
{
  uint16_t unSetting = (EEPROM.read(nStart))*256;
  unSetting += EEPROM.read(nStart+1);
  return unSetting;
}