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eeprom.c
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eeprom.c
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// This file has been prepared for Doxygen automatic documentation generation.
/*! \file ********************************************************************
*
* Atmel Corporation
*
* \li File: eeprom.c
* \li Compiler: IAR EWAAVR 3.10c
* \li Support mail: avr@atmel.com
*
* \li Supported devices: All devices with split EEPROM erase/write
* capabilities can be used.
* The example is written for ATmega48.
*
* \li AppNote: AVR103 - Using the EEPROM Programming Modes.
*
* \li Description: Example on how to use the split EEPROM erase/write
* capabilities in e.g. ATmega48. All EEPROM
* programming modes are tested, i.e. Erase+Write,
* Erase-only and Write-only.
*
* $Revision: 1.6 $
* $Date: Friday, February 11, 2005 07:16:44 UTC $
****************************************************************************/
#include <avr/io.h>
#include <avr/interrupt.h>
/* These EEPROM bits have different names on different devices. */
#ifndef EEPE
#define EEPE EEWE //!< EEPROM program/write enable.
#define EEMPE EEMWE //!< EEPROM master program/write enable.
#endif
/* These two are unfortunately not defined in the device include files. */
#define EEPM1 5 //!< EEPROM Programming Mode Bit 1.
#define EEPM0 4 //!< EEPROM Programming Mode Bit 0.
/* Define to reduce code size. */
#define EEPROM_IGNORE_SELFPROG //!< Remove SPM flag polling.
/*! \brief Read byte from EEPROM.
*
* This function reads one byte from a given EEPROM address.
*
* \note The CPU is halted for 4 clock cycles during EEPROM read.
*
* \param addr EEPROM address to read from.
* \return The byte read from the EEPROM address.
*/
unsigned char eeprom_get_char( unsigned int addr )
{
do {} while( EECR & (1<<EEPE) ); // Wait for completion of previous write.
EEAR = addr; // Set EEPROM address register.
EECR = (1<<EERE); // Start EEPROM read operation.
return EEDR; // Return the byte read from EEPROM.
}
/*! \brief Write byte to EEPROM.
*
* This function writes one byte to a given EEPROM address.
* The differences between the existing byte and the new value is used
* to select the most efficient EEPROM programming mode.
*
* \note The CPU is halted for 2 clock cycles during EEPROM programming.
*
* \note When this function returns, the new EEPROM value is not available
* until the EEPROM programming time has passed. The EEPE bit in EECR
* should be polled to check whether the programming is finished.
*
* \note The EEPROM_GetChar() function checks the EEPE bit automatically.
*
* \param addr EEPROM address to write to.
* \param new_value New EEPROM value.
*/
void eeprom_put_char( unsigned int addr, unsigned char new_value )
{
char old_value; // Old EEPROM value.
char diff_mask; // Difference mask, i.e. old value XOR new value.
cli(); // Ensure atomic operation for the write operation.
do {} while( EECR & (1<<EEPE) ); // Wait for completion of previous write.
#ifndef EEPROM_IGNORE_SELFPROG
do {} while( SPMCSR & (1<<SELFPRGEN) ); // Wait for completion of SPM.
#endif
EEAR = addr; // Set EEPROM address register.
EECR = (1<<EERE); // Start EEPROM read operation.
old_value = EEDR; // Get old EEPROM value.
diff_mask = old_value ^ new_value; // Get bit differences.
// 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; // Set EEPROM data register.
EECR = (1<<EEMPE) | // Set Master Write Enable bit...
(0<<EEPM1) | (0<<EEPM0); // ...and Erase+Write mode.
EECR |= (1<<EEPE); // Start Erase+Write operation.
} else {
// Now we know that all bits should be erased.
EECR = (1<<EEMPE) | // Set Master Write Enable bit...
(1<<EEPM0); // ...and Erase-only mode.
EECR |= (1<<EEPE); // Start Erase-only operation.
}
} 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; // Set EEPROM data register.
EECR = (1<<EEMPE) | // Set Master Write Enable bit...
(1<<EEPM1); // ...and Write-only mode.
EECR |= (1<<EEPE); // Start Write-only operation.
}
}
sei(); // Restore interrupt flag state.
}
// Extensions added as part of Grbl
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));
}
// end of file