EEPROM — `pymcu.hal.eeprom`#

from pymcu.hal.eeprom import EEPROM

Non-volatile byte storage using the internal EEPROM. EEPROM is a zero-cost @inline class — all reads and writes compile to bare register-level sequences with no SRAM overhead.

Capacity by chip#

Chip	Size	Address range	Write latency
ATmega328P	1024 bytes	`0x000`–`0x3FF`	~3.4 ms
ATmega2560	4096 bytes	`0x000`–`0xFFF`	~3.4 ms
ATmega32U4	1024 bytes	`0x000`–`0x3FF`	~3.4 ms
ATtiny85/45/25	512/256/128 bytes	varies	~3.4 ms

Endurance: 100 000 write/erase cycles per cell. Data retention: 20+ years at 25 °C.

class `EEPROM`#

`EEPROM()`#

Creates an EEPROM handle. No registers are written at construction time.

Methods#

Method	Signature	Description
`write`	`write(addr: uint16, value: uint8)`	Write one byte. Blocks ~3.4 ms for write to complete.
`read`	`read(addr: uint16) -> uint8`	Read one byte. Returns immediately.

Example#

from pymcu.hal.eeprom import EEPROM
from pymcu.types import uint8, uint16

def main():
    ee = EEPROM()

    # Persist a calibration offset
    ee.write(0x00, 42)

    # Read it back after power cycle
    cal: uint8 = ee.read(0x00)

Wear-leveling#

Each cell has a finite write endurance (~100 k cycles). For values that change frequently (counters, log entries), distribute writes across multiple addresses rather than hitting the same cell repeatedly.

ATmega328P register map#

Register	Address	Description
`EEARH`	`0x42`	EEPROM Address High
`EEARL`	`0x41`	EEPROM Address Low
`EEDR`	`0x40`	EEPROM Data Register
`EECR`	`0x3F`	EEPROM Control Register (EEPE, EEMPE, EERIE, EEPM)