Uploading Repetier firmware to Arduino? I have a prusa i3 and have been trying to calibrate it. I have been trying to upload the new steps per mm and I get to done uploading. However when I go into Repetier host and type M503 to get the printers settings it still shows the steps as 100 for the y axis, it needs to be 96.1810. I am using ramps 1.4 I think, with Adrunio mega 2560. If I am remembering this correctly isn't there something you have to do when uploading a new sketch like hold the rest button or something?
If your firmware doesn't store values you modified after flashing, for example using Repetier's option "Firmware EEPROM configuration", you probably didn't define EEPROM setting in Marlin. 

To do this you have to uncomment the option in Marlin's Configuration.h:

// EEPROM
// The microcontroller can store settings in the EEPROM, e.g. max velocity...
// M500 - stores parameters in EEPROM
// M501 - reads parameters from EEPROM (if you need reset them after you changed them temporarily).
// M502 - reverts to the default "factory settings".  You still need to store them in EEPROM afterwards if you want to.
//define this to enable EEPROM support
  #define EEPROM_SETTINGS

#if ENABLED(EEPROM_SETTINGS)
// To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
#define EEPROM_CHITCHAT // Please keep turned on if you can.
#endif


Check that the lines #define EEPROM_SETTINGS and #define EEPROM_CHITCHAT are both uncommented (i.e. defined)