Xmega Application Note

ATxmega256A3_EEPROM.c

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/* This file has been prepared for Doxygen automatic documentation generation.*/
#include "avr_compiler.h"

#define PAGESIZE 32 //EEPROM page size


void EEPROM_write_page (uint8_t * page, uint8_t page_no);

/*
 * Please note that no other interrupts can have the highest
 * interrupt level than the EEPROM interrupt!
 */

/* Interrupt handler for the EEPROM write "done" interrupt */
ISR(NVM_EE_vect)
{
        /* Disable the EEPROM interrupt */
        NVM.INTCTRL = (NVM.INTCTRL & ~NVM_EELVL_gm);
        return;
}

/*@main to test that the function works
*/
int main (void)
{
        uint8_t eeprom_page[PAGESIZE];

        /* Just create some data to put in the EEPROM */
        for(int i = 0; i < PAGESIZE; i++)
        {
                eeprom_page[i] = i;
        }
        
        /* Call to the write page function */
        /* Write the contents of eeprom_page to EEPROM page nr. 2 */
        EEPROM_write_page(eeprom_page, 2);
        
        
        while(1){}      
}
/*@
Function for writing a page to EEPROM while putting the device to sleep
page: pointer to the first address of the page to be written
page_no: which page number to write to EEPROM.
*/
void EEPROM_write_page (uint8_t * page, uint8_t page_no)
{
        /* Set the NVM command to load to the EEPROM buffer */
        NVM.CMD = NVM_CMD_LOAD_EEPROM_BUFFER_gc;
        
        /* Max buffersize is PAGESIZE, hence the upper addresses are not needed */
        NVM.ADDR2 = 0;
        NVM.ADDR1 = 0;  

        /* Load buffer with data */
        for(int i = 0; i < PAGESIZE; i++)
        {
                /* Set the location where data is going to be put in the buffer */
                NVM.ADDR0 = i;
                /* Writing to the DATA register will trigger a write to the buffer */
                NVM.DATA0 = page[i];
        }
        
        /* Load the NVM command with erase and then write EEPROM page */
        NVM.CMD = NVM_CMD_ERASE_WRITE_EEPROM_PAGE_gc;

        /* Calculate address */
        uint16_t address = (uint16_t)(page_no*PAGESIZE);

        /* Set address to write to. */
        NVM.ADDR0 = address & 0xFF;
        NVM.ADDR1 = (address >> 8) & 0x1F;
        NVM.ADDR2 = 0x00;

        /* Save the Sleep register */
        uint8_t sleepCtr = SLEEP.CTRL;
        /* Set sleep mode to IDLE */
        SLEEP.CTRL = (SLEEP.CTRL & ~SLEEP.CTRL) | SLEEP_SMODE_IDLE_gc; 
        /* Save the PMIC Status and control registers */
        uint8_t statusStore = PMIC.STATUS;                                                              
        uint8_t pmicStore = PMIC.CTRL;          
        
        /* Enable only the highest level of interrupts */                                                                       
        PMIC.CTRL = (PMIC.CTRL & ~PMIC_HILVLEN_bm) | PMIC_HILVLEN_bm;
        /* Save SREG for later use */
        uint8_t globalInt = SREG;
        /* Enable global interrupts */
        sei();
        /* Set sleep enabled */
        SLEEP.CTRL |= SLEEP_SEN_bm; 
        /* Save eeprom interrupt settings for later */ 
        uint8_t eepromintStore = NVM.INTCTRL;
        
        
        /* Write the "safety code" to the CCP regiter */
        /* EEPROM write has to be executed within 4 cycles */
        CCP = CCP_IOREG_gc;
        /* Execute command to write buffer page to EEPROM */
        NVM.CTRLA = NVM_CMDEX_bm;
        /* Enable EEPROM interrupt */
        NVM.INTCTRL =  NVM_EELVL0_bm | NVM_EELVL1_bm;
        /* Sleep before 2.5uS has passed */
        __sleep();
        
        
        /* Restore sleep settings */
        SLEEP.CTRL = sleepCtr;
        /* Restore PMIC status and control registers */
        PMIC.STATUS = statusStore;
        PMIC.CTRL = pmicStore;
        /* Restore EEPROM interruptsettings */
        NVM.INTCTRL = eepromintStore;
        /* Restore global interrupt settings */
        SREG = globalInt;
}