EEPROM

The beginning part is used for Settings (Interactive Mode), so when used together, it is recommended to use the latter half of the addresses. The amount of space consumed by the settings (Interactive Mode) depends on its implementation. Even with minimal settings, the first 256 bytes are used, so it is recommended to use addresses after that.

Methods

read()

uint8_t read(uint16_t address)

Reads data corresponding to address from the EEPROM.

write()

void write(uint16_t address, uint8_t value)

Writes value to address in the EEPROM.

update()

void update(uint16_t address, uint8_t value)

Performs writing similar to write(), but first reads the data at address and writes only if it is different from value. This is used to reduce the number of write cycles considering the EEPROM’s rewrite lifespan.

get_stream_helper()

auto&& get_stream_helper()
// The return type is long, so it is abbreviated as auto&&.

Obtains a helper object to perform read and write operations using the later described mwx::stream.

Input/output using the mwx::stream interface

Through the stream_helper helper object, use operators and methods of mwx::stream. Using mwx::stream allows reading and writing of integer types such as uint16_t and uint32_t, fixed-length arrays of uint8_t, and formatted output via format() objects.

auto&& strm = EEPROM.get_stream_helper();
// The helper object's type name is long, so auto&& is used to resolve it.

You can use the << operator and other interfaces defined in mwx::stream with this object.

strm.seek(1024); // Move to byte 1024

strm << format("%08x", 12345678); // Record 12345678 as an 8-character hexadecimal
strm << uint32_t(0x12ab34cd);     // Record 4 bytes of 0x12ab34cd
uint8_t msg_hello[16] = "HELLO WORLD!";
strm << msg_hello;                // Record byte sequence "HELLO WORLD!" (no terminator)

// Result
// 0400: 30 30 62 63 36 31 34 65 12 ab 34 cd 48 45 4c 4c
//        0  0  b  c  6  1  4  e  0x12ab34cd  H  E  L  L
// 0410: 4f 20 57 4f 52 4c 44 21 00 00 00 00 ff ff ff ff
//        O SP  W  O  R  L  D  !

Using .seek(), the EEPROM address is moved to 1024.

The above writes an 8-byte string (00bc614e), a 4-byte integer (0x12ab34cd), a 16-byte byte array (HELLO WORLD!...), and a 1-byte terminator.

strm.seek(1024);

uint8_t msg1[8];
strm >> msg1;
Serial << crlf << "MSG1=" << msg1;
// MSG1=00bc614e

uint32_t var1;
strm >> var1;
Serial << crlf << "VAR1=" << format("%08x", var1);
// VAR1=12ab34cd

uint8_t msg2[16]; // Number of characters in "HELLO WORLD!"
strm >> msg2;
Serial << crlf << "MSG2=" << msg2;
// MSG2=HELLO WORLD!

Using .seek(), the EEPROM address is moved to 1024.

Reads the previously written data sequence. Reads an 8-byte string, a 4-byte integer, and a 16-byte string in order using the >> operator.