112 lines
2.4 KiB
C
112 lines
2.4 KiB
C
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/**
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* \file persistentCounter.c
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* \author Daniel Otte
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* \brief a persistent 24-bit counter in EEPROM for ATmega µC
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*
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*/
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#include <stdint.h>
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#include <avr/interrupt.h> /* cli() & sei() */
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#include <avr/eeprom.h>
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#include "../config.h"
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#ifdef ERROR_HANDLING
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#include "error-handling.h"
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#define PERSISTENT_COUNTER_OVERFLOW (void*)0, 2,4,1
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#define PERSISTENT_COUNTER_WRITER_ERROR (void*)0, 2,4,2
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#endif
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#define RING_SIZE 168
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uint8_t ring_idx = 0xff;
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uint16_t EEMEM B08_23;
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uint8_t EEMEM B0_7[RING_SIZE];
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#ifdef INIT_EEPROM
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void init_buffer(void){
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uint8_t i;
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eeprom_busy_wait();
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eeprom_write_word(&B08_23, 0x0000);
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for(i=0; i<RING_SIZE; ++i){
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eeprom_busy_wait();
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eeprom_write_byte(&(B0_7[i]), 0x00);
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}
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}
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#endif
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void percnt_init(void){
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uint8_t i;
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uint8_t maxidx=0;
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uint8_t t,max=eeprom_read_byte(&(B0_7[0]));
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#ifdef INIT_EEPROM
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if (eeprom_read_word(&B08_23)==0xFFFF){ /* test if the 2 MSB == 0xFFFF*/
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if (eeprom_read_word((uint16_t*)&(B0_7[0]))==0xFFFF) /* test the first to bytes of ringbuffer*/
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init_buffer();
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}
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#endif
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for(i=0; i<RING_SIZE; ++i){ /* this might be speed up, but such optimisation could lead to timing attacks */
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eeprom_busy_wait();
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t=eeprom_read_byte(&(B0_7[i]));
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if(t==max+1){
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max=t;
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maxidx=i;
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}
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}
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ring_idx = (maxidx==RING_SIZE)?0:maxidx;
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}
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uint32_t percnt_get(void){
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uint32_t ret=0;
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if(ring_idx==0xff)
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percnt_init();
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cli();
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eeprom_busy_wait();
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ret=eeprom_read_word(&B08_23)<<8;
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eeprom_busy_wait();
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ret |= eeprom_read_byte(&(B0_7[ring_idx]));
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sei();
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return ret;
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}
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void percnt_inc(void){
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/* we must make this resistant agaist power off while this is running ... */
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uint32_t u;
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if(ring_idx==0xff)
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percnt_init();
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u = percnt_get();
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cli();
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/* it's important to write msb first! */
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if((u&0x000000ff) == 0xff){
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if((u&0x0000ffff) == 0xffff){
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if((u&0x00ffffff) == 0xffffff){
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/* we can turn the lights off now. it's time to die */
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#ifdef ERROR_HANDLING
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error(PERSISTENT_COUNTER_OVERFLOW);
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#endif
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}
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eeprom_busy_wait();
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eeprom_write_byte(&(((uint8_t*)&B08_23)[1]),((u+1)>>16)&0xff);
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}
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eeprom_busy_wait();
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eeprom_write_byte(&(((uint8_t*)&B08_23)[0]),((u+1)>>8)&0xff);
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}
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/* set least significant byte (in ringbuffer) */
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ring_idx = (ring_idx+1)%RING_SIZE;
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eeprom_busy_wait();
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eeprom_write_byte(&(B0_7[ring_idx]),(u+1)&0xff);
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eeprom_busy_wait();
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if(u+1 != percnt_get()){
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#ifdef ERROR_HANDLING
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error(PERSISTENT_COUNTER_WRITER_ERROR);
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#endif
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}
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sei();
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}
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