avr-eeprom-wear-leveling

Overview

Header-only C++ implementation of Danny's algorithm of EEPROM wear leveling for AVR microcontrollers.

Specification

• support for multiple separate EEPROM wear-leveling blocks,
• can coexist with other values stored in EEPROM (EEMEM),
• synchronous (not interrupt-driven) or asynchronous modes,
• protected against write corruption.

Classes

Repository implements 2 different approaches to wear-leveling and one async version:

• EEPROMBitSentinelWearLeveling
• EEPROMByteSentinelWearLeveling
• EEPROMByteSentinelWearLevelingAsync (requires src/eeprom_async.cpp)

EEPROMBitSentinelWearLeveling

Sentinel bit included in MSB of the first byte.

Requirements:

• MSB of the first byte of data record can't be used. For example:

struct Record {
	uint16_t val1;
	uint16_t val2;
};

Most significant bit of val1 (0x8000) should not be used as it will be cleared. val2 can use all bits (note the following requirement),

• record can't have all bytes equal to 0xff as it would not allow detecting fresh EEPROM.

Pros:

• most space-efficient way,

Cons:

• one bit lost for sentinel,
• any record has to have at least 1 bit set to 0.

EEPROMByteSentinelWearLeveling

Separate byte for sentinel.

Pros:

• No restrictions on Record's fields' values,

Cons:

• Full byte lost for the sentinel.

EEPROMByteSentinelWearLevelingAsync

Similar to EEPROMByteSentinelWearLeveling, except that save() method executes asynchronously (using interrupts).

API

All three classes exposes the same API:

void EEPROMByteSentinelWearLeveling::save(TRecord& record);

record - record to be saved to EEPROM,

bool EEPROMByteSentinelWearLeveling::load(TRecord& record);

record - record loaded from EEPROM,
return value - true, if record was loaded successfully, false otherwise.

Example

#include <avr/eeprom.h>
#include <EEPROMByteSentinelWearLeveling.h>

#pragma pack(1)
struct Record {
	uint16_t val1;
	uint16_t val2;
};
#pragma pack()

// EEMEM uint8_t eepromBlock[sizeof(Record) * 20]; // for bit version
EEMEM uint8_t eepromBlock[(sizeof(Record) + 1) * 20];

// EEPROMBitSentinelWearLeveling<Record, sizeof(eepromBlock), eepromBlock> eeprom;
EEPROMByteSentinelWearLeveling<Record, sizeof(eepromBlock), eepromBlock> eeprom;
// EEPROMByteSentinelWearLevelingAsync<Record, sizeof(eepromBlock), eepromBlock> eeprom;

void main() {
  Record record;
  
  if (eeprom.load(record)) {
    // record loaded
    record.val1++;
  }
  else {
    // no record loaded, EEPROM is clean
    record.val1 = 1;
    record.val2 = 0;
  }
  
  eeprom.save(record);
}