Auto_Bed_Leveling: Enhanced G29 command

[Roxy]

As a result of that experience, I wrote a small piece of firmware to invalidate the EEPROM so the setting are not taken from it unless you actually do an implicit store to the EEPROM. I think the original authors of Marlin were trying to save a little firmware space and did not include it. But if you are making changes to your Configuration.h file, it gets annoying having to load the default settings and save them each time. Its easier to just invalidate the EEPROM (with a M499) command:

In Marlin_Main.cpp:

case 499: // Invalidate the M500 Store settings in EEPROM command
{
Invalidate_EEPROM_Settings(); // Roxy added function to guarintee we are using
// the default values defined in the firmware!
}
break;

In ConfigurationStore.cpp:

void Invalidate_EEPROM_Settings()
{
char bogus_ver[4] = "xyz";
char confirmation[4] = "???";
int i=EEPROM_OFFSET;

EEPROM_WRITE_VAR(i,bogus_ver);

i=EEPROM_OFFSET;
EEPROM_READ_VAR(i,confirmation); //read stored version

if (strncmp(bogus_ver, confirmation,3) == 0)
SERIAL_PROTOCOLLNPGM("EEPROM Settings invalidated.");
else {
SERIAL_PROTOCOLLNPGM("EEPROM Settings not invalidated.");
SERIAL_PROTOCOLPGM("Read Version: [");
SERIAL_PROTOCOL(confirmation);
SERIAL_PROTOCOLLNPGM("]\n");
}
}

In ConfigurationStore.h:
#ifdef EEPROM_SETTINGS
void Invalidate_EEPROM_Settings(); // Roxy routine to guarantee we are using default firmware values
void Config_StoreSettings();
void Config_RetrieveSettings();
#else
FORCE_INLINE void Config_StoreSettings() {}
FORCE_INLINE void Config_RetrieveSettings() { Config_ResetDefault(); Config_PrintSettings(); }
#endif