Remote Access Control

memory.c

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// This file has been prepared for Doxygen automatic documentation generation.
#include "memory.h"
#include "common.h"
#include "config.h"



/* --- EEPROM memory contents --- */

// Variables at absolute addresses are defined in the header file only.



/* --- SRAM memory contents --- */

byte cryptoBlock[ BLOCK_SIZE + 1 ];
union SharedBlock sharedBlock;



/* --- Associated functions --- */

void initializeMessage(void)
{
        // The preamble is used as a synch-and-start indicator for
        // the RF receiver.
        sharedBlock.messagePayload.preamble = 0xfe; // 11111110
        sharedBlock.messagePayload.serialNo = serialNo;
}



void createMessage( COMMAND_CODE_TYPE commandCode )
{
        sharedBlock.messagePayload.commandCode = commandCode;
        sharedBlock.messagePayload.counterValue = nextCounterValue;
}



static volatile byte counterBytesLeft = 0;



void startCounterUpdate()
{
        // Make sure EEPROM is ready.
        do {} while( EECR & (1<<EEWE) );
        // Prepare control variables.
        EEDR = 0xff; // 0xff indicates that we just started.
        EEAR = (uint16_t) &nextCounterValue;
        counterBytesLeft = SEQ_COUNTER_BYTES;
        // Enable EEPROM Ready Interrupt.
        EECR |= (1<<EERIE);
}



void waitForCounterUpdate()
{
        while( counterBytesLeft ) { __sleep(); }
}



/* --- ISR and variables for updating counter value --- */

#pragma vector = EE_RDY_vect
__interrupt void eepromReadyHandler(void)
{
        // If previous byte wrapped to 0x00, increase address.
        if( EEDR == 0x00 ) {
                ++EEAR;
        }

        // Read old value.
        EECR |= (1<<EERE);
        // Increase.
        ++EEDR;
        // If no overflow, no bytes left to update.
        if( EEDR != 0x00 ) {
                counterBytesLeft = 0;
                EECR &= ~(1<<EERIE); // Disable further interrupts.
        } else {
                --counterBytesLeft;
        }
        
        // Start writing.
        EECR |= (1<<EEMWE);
        EECR |= (1<<EEWE);
}