eeprom.c

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// This file has been prepared for Doxygen automatic documentation generation.
#include <avr/io.h>
#include <avr/interrupt.h>

#ifndef EEPE
        #define EEPE  EEWE  
        #define EEMPE EEMWE 
#endif

#define EEPM1 5 
#define EEPM0 4 


#define EEPROM_IGNORE_SELFPROG 


unsigned char eeprom_get_char( unsigned int addr )
{
    do {} while( EECR & (1<<EEPE) ); 
    EEAR = addr; 
    EECR = (1<<EERE); 
    return EEDR; 
}

void eeprom_put_char( unsigned int addr, unsigned char new_value )
{
    char old_value; 
    char diff_mask; 

    cli(); 
    
    do {} while( EECR & (1<<EEPE) ); 
    #ifndef EEPROM_IGNORE_SELFPROG
    do {} while( SPMCSR & (1<<SELFPRGEN) ); 
    #endif
    
    EEAR = addr; 
    EECR = (1<<EERE); 
    old_value = EEDR; 
    diff_mask = old_value ^ new_value; 
    
    // Check if any bits are changed to '1' in the new value.
    if( diff_mask & new_value ) {
        // Now we know that _some_ bits need to be erased to '1'.
        
        // Check if any bits in the new value are '0'.
        if( new_value != 0xff ) {
            // Now we know that some bits need to be programmed to '0' also.
            
            EEDR = new_value; 
            EECR = (1<<EEMPE) | 
                   (0<<EEPM1) | (0<<EEPM0); 
            EECR |= (1<<EEPE);  
        } else {
            // Now we know that all bits should be erased.

            EECR = (1<<EEMPE) | 
                   (1<<EEPM0);  
            EECR |= (1<<EEPE);  
        }
    } else {
        // Now we know that _no_ bits need to be erased to '1'.
        
        // Check if any bits are changed from '1' in the old value.
        if( diff_mask ) {
            // Now we know that _some_ bits need to the programmed to '0'.
            
            EEDR = new_value;   
            EECR = (1<<EEMPE) | 
                   (1<<EEPM1);  
            EECR |= (1<<EEPE);  
        }
    }
    
    sei(); 
}


void memcpy_to_eeprom_with_checksum(unsigned int destination, char *source, unsigned int size) {
  unsigned char checksum = 0;
  for(; size > 0; size--) { 
    checksum = (checksum << 1) || (checksum >> 7);
    checksum += *source;
    eeprom_put_char(destination++, *(source++)); 
  }
  eeprom_put_char(destination, checksum);
}

int memcpy_from_eeprom_with_checksum(char *destination, unsigned int source, unsigned int size) {
  unsigned char data, checksum = 0;
  for(; size > 0; size--) { 
    data = eeprom_get_char(source++);
    checksum = (checksum << 1) || (checksum >> 7);
    checksum += data;    
    *(destination++) = data; 
  }
  return(checksum == eeprom_get_char(source));
}