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// this script posted by BroHogan at the Arduino playground
// see Re: I2C Code for Serial EEPROMs at https://forum.arduino.cc/index.php?topic=85382.0
/* Simple read & write to a 24LC series EEPROM using the Wire library.
* Addresses are ints - 0000-7FFF (32767) Data is bytes (8 bits x 32767 = 256K)
* Functions for R/W of single byte or a page of bytes. Max page payload is 28 bytes.
* SETUP: _ _
* Arduino GND- A0-|oU |-Vcc to Arduino Vcc
* Arduino GND- A1-| |-WP to GND for now. Set to Vcc for write protection.
* Arduino GND- A2-| |-SCL to Arduino 5
* Arduino GND-Vss-| |-SDA to Arduino 4
* --- (A2, A1, A0 to GND for 1010000 (0x50) address.)
* If set to Vcc adds to address (1010,A2,A1,A0)
*/
#include <Wire.h>
#define EEPROM_ADDR 0x57 // I2C Buss address of the AT24C32 4K EEPROM on the DS3231 RTC module (may also be 0x56!)
void setup(){
Wire.begin(); // join I2C bus
Serial.begin(9600);
// TESTS FOR EACH FUNCTION BEGIN HERE
Serial.println("Writing Test:");
for (int i=0; i<20; i++){ // loop for first 20 slots
i2c_eeprom_write_byte(EEPROM_ADDR,i,i+65); // write address + 65 A or 97 a
Serial.print(". ");
delay(10); // NEED THIS DELAY!
}
Serial.println("");
delay(500);
Serial.println("Reading Test:");
for (int i=0; i<20; i++){ // loop for first 20 slots
Serial.write(i2c_eeprom_read_byte(EEPROM_ADDR, i));
Serial.print(" ");
}
// setup for page tests . . .
byte PageData[30]; // array that will hold test data for a page
byte PageRead[30]; // array that will hold result of data for a page
for (int i=0; i<30; i++){ // zero both arrays for next test
PageData[i] = 0;
PageRead[i] = 0;
}
Serial.println("");
for (int i=0; i<30; i++) PageData[i] = i+33; // fill up array for next test char 33 = !
Serial.println("Writing Page Test:");
i2c_eeprom_write_page(EEPROM_ADDR, 100, PageData, 28 ); // 28 bytes/page is max
Serial.println("Reading Page Test:");
i2c_eeprom_read_buffer( EEPROM_ADDR, 100, PageRead, 28);
for (int i=0; i<28; i++){
Serial.write(PageRead[i]); // display the array read
Serial.print(" ");
}
}
void loop(){
}
void i2c_eeprom_write_byte( int deviceaddress, unsigned int eeaddress, byte data ) {
int rdata = data;
Wire.beginTransmission(deviceaddress);
Wire.write((int)(eeaddress >> 8)); // Address High Byte
Wire.write((int)(eeaddress & 0xFF)); // Address Low Byte
Wire.write(rdata);
Wire.endTransmission();
}
// Address is a page address, 6-bit (63). More and end will wrap around
// But data can be maximum of 28 bytes, because the Wire library has a buffer of 32 bytes
void i2c_eeprom_write_page( int deviceaddress, unsigned int eeaddresspage, byte* data, byte length ) {
Wire.beginTransmission(deviceaddress);
Wire.write((int)(eeaddresspage >> 8)); // Address High Byte
Wire.write((int)(eeaddresspage & 0xFF)); // Address Low Byte
byte c;
for ( c = 0; c < length; c++)
Wire.write(data[c]);
Wire.endTransmission();
delay(10); // need some delay
}
byte i2c_eeprom_read_byte( int deviceaddress, unsigned int eeaddress ) {
byte rdata = 0xFF;
Wire.beginTransmission(deviceaddress);
Wire.write((int)(eeaddress >> 8)); // Address High Byte
Wire.write((int)(eeaddress & 0xFF)); // Address Low Byte
Wire.endTransmission();
Wire.requestFrom(deviceaddress,1);
if (Wire.available()) rdata = Wire.read();
return rdata;
}
// should not read more than 28 bytes at a time!
void i2c_eeprom_read_buffer( int deviceaddress, unsigned int eeaddress, byte *buffer, int length ) {
Wire.beginTransmission(deviceaddress);
Wire.write((int)(eeaddress >> 8)); // Address High Byte
Wire.write((int)(eeaddress & 0xFF)); // Address Low Byte
Wire.endTransmission();
Wire.requestFrom(deviceaddress,length);
//int c = 0;
for ( int c = 0; c < length; c++ )
if (Wire.available()) buffer[c] = Wire.read();
}
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