Help understanding Marlin Flash vs Eeprom

When I make a change to my Marlin firmware and upload it to my Ramps 1.4/Arduino Mega 2560 board, where exactly is the firmware being stored? In flash memory or eeprom? I ask because it seems that whenever I make a change to the files and upload them with the Arduino IDE, the changes don't seem to be in effect. Do I have to turn off then on the machine? Or is it being loaded to eeprom and I have to 'restore' them with M502. Are they automatically used when the board is reset by Arduino IDE after the upload?

Any info is appreciated.

You'll have to restore the defaults (M502?) then store those in the EEPROM (M500 or M501 I can't remember which it is), if EEPROM is enabled, then you'll get whatever you last stored there.

Edited 2 time(s). Last edit at 10/06/2012 09:07PM by Polygonhell.

By this:

Quote
PolygonHell
if EEPROM is enabled

do you mean:

Quote

//define this to enable eeprom support
//#define EEPROM_SETTINGS
//to disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
// please keep turned on if you can.
//#define EEPROM_CHITCHAT

from Marlin?

If that is what you mean, and I leave eeprom turn off, then any changes made are only stored in Flash ?

Yes - my understanding is that if you do not enable eeprom, your data is only stored in flash and will be overwritten each time you re-upload the firmware.

If you enable eeprom, then after each reset - or when you enter m501 - the eeprom values are copied into flash. So you cannot change settings by modifying source code and ten uploading ( actually I think there is a way by playing around with the version number).

The advantage to eeprom is tat you can tinker with your settings easily - every eeprom parameter is settable with an m command - and easily revert back to your standard settings if things don't work out. If you like your new settings, there is another m50x command to commit everything to eeprom.

Through trial and error, I can confirm what jbernardis is saying. Personally, I prefer to write all my changes into firmware on PC, flash to arduino and then forget about the rest. Especially during testing.