eeVar lets to define, use, read and write variables stored in AVR's EEPROM memory and configure the AVR device using data stored in EEPROM

EEPROM_VAR(var_type, var_name)

Defines EEPROM stored variable of type var_type, named var_name giving it a a value to be strored in EEPROM. This variable should be initialized using EEPROM_READ() before use.

EEPROM_VAR(uint8_t, ledBrightness) = 127;

main()
{
  EEPROM_READ(ledBrightness);
  setPWM(ledBrightness);
}

EEPROM_AUTO_VAR(var_type, var_name)

Defines EEPROM stored variable of type var_type, named var_name with a value strored in EEPROM. This value will be automaticaly read into var_name in RAM in .init8 section just before the main() function starts execution. Then, the definition alone is enough to get pre-initialized variable ready to use as soon as the program starts.

EEPROM_AUTO_VAR(uint8_t, ledBrightness) = 127;

main()
{
  setPWM(ledBrightness);
}

EEPROM_READ(x)

Reads value of a variable from EEPROM to RAM memory. This must be a variable defined with EEPROM_VAR or 'EEPROM_AUTO_VAR` macros.

EEPROM_VAR(uint8_t, ledBrightness) = 127;

main()
{
  EEPROM_READ(ledBrightness);
  setPWM(ledBrightness);
}

EEPROM_WRITE(x)

Writes value of a variable from RAM to EEPROM memory. This must be a variable defined with EEPROM_VAR or EEPROM_AUTO_VAR macros.

EEPROM_AUTO_VAR(uint8_t, ledBrightness) = 127;

main()
{
  int newLedBrightness = checkButtons(ledBrightness);
  setPWM(newLedBrightness);
  if (newLedBrightness != ledBrightness)
  {
    ledBrightness= newLedBrightness;
    EEPORM_WRITE(ledBrightness); // EEPORM_WRITE(newLedBrightness) wouldn't work
  }
}

EEPROM_CONFIG(name)

Defines set of configuration data as a vetor filled with EEPROM_SETUP entries. This may be complete device initialization or partial configuration so there can be many sets in system.

Setting just few registers directly in code may be more efficient than using EEPROM config.

EEPROM_SETUP(reg, value)

Defines register/value as a pair of configuration set.

EEPROM_CONFIGURE(name)

Rewrites configuration set from EEPROM to AVR's registers. Since it calls a function which does the job in loop the amount of used program memory does not depend on the number of entries in config data set. This technique may save some program bytes at a cost of EEPROM memory. On devices with small prghram memories it may be crucial.

EEPORM_CONFIG(pwmEnable) =
{
  EEPROM_SETUP(PWMREG0, 1 << PWM_EN | 1 << PWM_PRESC_2),
  EEPROM_SETUP(PWMMAX, 128)
};

main()
{
  EEPROM_CONFIGURE(pwmEnable);
}