EpoxyEepromEsp

EpoxyEepromEsp

An implementation of EEPROM that runs on Linux (or other POSIX-like system) using EpoxyDuino (https://github.com/bxparks/EpoxyDuino). There are at least two versions of the EEPROM API:

• AVR flavor: AVR, STM32, Teensy, and potentially others
  • https://github.com/arduino/ArduinoCore-avr/blob/master/libraries/EEPROM/src/EEPROM.h
• ESP flavor: ESP8266 and ESP32,
  • https://github.com/esp8266/Arduino/blob/master/libraries/EEPROM/EEPROM.h

This library implements the ESP flavor of the EEPROM API. The EEPROM contents are buffered in memory, then saved to a file called epoxyeepromdata in the current directory upon the EEPROM.commit() or EEPROM.end() methods.

See EpoxyEepromAvr for the AVR version.

Usage

EEPROM API

This library provides most of the functions listed in EEPROM.h in the Arduino ESP8226 Core.

Makefile

When using the EpoxyDuino Makefile, the EpoxyEepromEsp library must be added to the ARDUINO_LIBS parameter, like this:

APP_NAME := EpoxyEepromEspTest
ARDUINO_LIBS := EpoxyEepromEsp ...
MORE_CLEAN := more_clean
include ../../../../EpoxyDuino.mk

Sample Code

#include <EpoxyEepromEsp.h>
#define EEPROM EpoxyEepromEspInstance

void write() {
  int address = 0;
  uint8_t value = 10;

  // write() method
  EEPROM.write(address, value);

  // operator[]
  EEPROM[address+1] = value+1;

  // commit() or end() required to persist to disk
  EEPROM.commit();
}

void read() {
  int address = 0;

  // read()
  uint8_t value = EEPROM.read(address);

  // operator[]
  value = EEPROM[address];
}

void detectAPI() {
  #if EPOXY_DUINO_EPOXY_EEPROM_ESP
    #warning Using EpoxyEepromEsp version of EEPROM
    EEPROM.begin(...);
    EEPROM.write(...);
    EEPROM.commit(...);
    EEPROM.read(...);
  #endif
}

void setup() {
  const int SIZE = 1024;

  // begin() required
  EEPROM.begin(SIZE);
  ...
}

void loop() {
}

Difference between ESP and AVR APIs

AVR Flavor

The AVR version of EEPROM provides 2 write functions:

EEPROM.write(address, value);
EEPROM.update(address, value);

where the update() only writes to the EEPROM if the new value is different than the old value stored in the EEPROM. This saves wear on the EEPROM.

The EEPROM.begin() and EEPROM.end() methods return iterators, which allows looping for the content of the EEPROM like this:

for (EEPtr p = EEPROM.begin(); p != EEPROM.end(); p++) {
  ...
}

ESP Flavor

The ESP8266 and ESP32 versions provide only the write() function:

EEPROM.write(address, value)

The begin() and end() methods mean completely different things on the ESP processors:

EEPROM.begin(size);

initializes the EEPROM storage space. The data written to the EEPROM using the write() method is buffered in memory until one of:

EEPROM.commit();
EEPROM.end();

is executed.

Environment Variable

By default, the content of the EEPROM is saved to a file named epoxyeepromdata in the current directory. You can change this by setting the EPOXY_EEPROM_DATA environment variable:

$ export EPOXY_EEPROM_DATA=/tmp/epoxyeepromdata