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EEPROM.write() endurance trade-off for high-frequency data logging on Arduino AVR
Rin Indigo
0 reputation · 27 Jul 2021, 00:50 UTC
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0 reputation · 27 Jul 2021, 00:50 UTC
On AVR-based Arduino boards, the EEPROM library provides EEPROM.write() for persisting individual bytes across resets. The underlying EEPROM cells have a finite write/erase endurance, typically specified around 100,000 cycles per byte, and reading an address does not consume that budget. For sketches that update the same address frequently—such as logging a counter or sensor value every second—the unconditional write behavior of EEPROM.write() raises a practical design boundary: without wear-leveling or a conditional update pattern, the byte may reach its endurance limit far sooner than the project's intended lifetime.
The uncertainty is where to draw the line between simplicity and endurance management. If the stored value rarely changes, skipping redundant writes is straightforward, but when the value changes on nearly every loop, the application must either accept the eventual cell failure, rotate across multiple addresses, or buffer writes in RAM before committing. Each approach changes both the code structure and the recovery behavior after an unexpected power loss.
What is the recommended configuration boundary for using EEPROM.write() on an ATmega328P when the target address is updated at a fixed interval? Should the design assume EEPROM.update() is sufficient to avoid unnecessary erase cycles, or is explicit wear-leveling required once the write frequency exceeds a certain threshold? How does the out-of-bounds read behavior for addresses beyond EEPROM.length() affect safe address rotation schemes?
Treat EEPROM.write() as consuming one erase/write cycle per call. On an ATmega328P, EEPROM provides 1,024 bytes at addresses 0 through 1,023, with a typical datasheet rating of about 100,000 cycles per byte. Reads do not consume endurance. Keep expected writes to any single address well below 100,000 over the product lifetime; a conservative planning target is 10,000 to 30,000 cycles per cell.
At one write per second to the same address, that is roughly 86,400 writes per day, approaching the rating in about 1.2 days. At one write per hour, it is roughly 8,760 writes per year, or more than 11 years at 100,000 cycles. These are estimates based on a typical rating, not per-cell guarantees.
EEPROM.update() reads first and skips the write when the byte is unchanged. It is sufficient only when consecutive logged values repeat often. If the value changes on nearly every fixed interval, update() still spends one full cycle on every change, so it does not solve endurance. Use explicit wear-leveling, RAM buffering with periodic commits, or external non-volatile storage instead.
Rotate across N addresses using index % EEPROM.length(). Write each sample at the current index, advance the index, and keep a sequence number or timestamp so the latest entry can be found after reboot. Do not read or write addresses greater than or equal to EEPROM.length(); the Arduino API does not define a safe sentinel or reliable wrap for out-of-bounds addresses, so they must not be used for rotation bounds or empty-slot detection.
arduinoEEPROM.length() returns 1,024 on your board.Missing diagnostic: does the logged value change on every fixed interval, or does it often repeat between writes? This determines whether EEPROM.update() alone is sufficient or whether wear-leveling is required.
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