====== I2C ======

I2C직렬 컴퓨터 버스주변기기를 연결하기 위해 사용된다.

{{http://i.imgur.com/99a3Z.png?300}}

데이터와 클럭은 pull-up

{{http://i.imgur.com/U3al8.png?300}}

Time

{{http://i.imgur.com/NtRbM.png?300}}

{{http://i.imgur.com/dgtdQ.png?300}}

===== 실제 실험 해보기 =====


arduino i2c 관련 핀
  * Analog4 - SDA
  * Analog5 - SCL

Time

{{http://i.imgur.com/VQtTJ.png?300}}

==== 24LC256, EEPROM ====

{{{
#include <Wire.h> //Include the Arduino I2C Library

void i2c_eeprom_write_byte( int deviceaddress, unsigned int eeaddress, byte data ) {
  int rdata = data;

  Wire.beginTransmission(deviceaddress);
  Wire.write((int)(eeaddress >> 8)); // MSB
  Wire.write((int)(eeaddress & 0xFF)); // LSB
  Wire.write(rdata);
  Wire.endTransmission();
}

void i2c_eeprom_write_page( int deviceaddress, unsigned int eeaddresspage, byte* data, byte length ) {
  Wire.beginTransmission(deviceaddress);
  Wire.write((int)(eeaddresspage >> 8)); // MSB
  Wire.write((int)(eeaddresspage & 0xFF)); // LSB

  byte c;
  for ( c = 0; c < length; c++)
    Wire.write(data[c]);

  Wire.endTransmission();
}

byte i2c_eeprom_read_byte( int deviceaddress, unsigned int eeaddress ) {
  byte rdata = 0xFF;

  Wire.beginTransmission(deviceaddress);
  Wire.write((int)(eeaddress >> 8)); // MSB
  Wire.write((int)(eeaddress & 0xFF)); // LSB
  Wire.endTransmission();
  Wire.requestFrom(deviceaddress,1);

  if (Wire.available()) rdata = Wire.read();

  return rdata;
}

void setup() {
  char data[] = "hello world";
  Wire.begin(); //Start I2C connections
  Serial.begin(9600);
  //i2c_eeprom_write_page(0x50, 0, (byte *)data, sizeof(data)); // write to EEPROM

  delay(10); //add a small delay

  Serial.println("Memory written");
}

void loop() {
  int addr=0; //EEPROM Address 0
  byte b = i2c_eeprom_read_byte(0x50, 0); // access the first address from the memory

  while (b!=0) {
   Serial.print((char)b); //print content to serial port
   addr++; //increase address
   b = i2c_eeprom_read_byte(0x50, addr); //access an address from the memory
 }

  Serial.println(" ");
  delay(2000);
}
}}}

master가 slave에 데이터를 보낸다.

{{http://i.imgur.com/lHqBZ.png?300}}

master가 slave의 데이터를 읽는다.

{{http://i.imgur.com/NE9xJ.png?300}}

==== Tmp102 ====
{{{

#include <Wire.h>
int tmp102Address = 0x48;

void setup(){
  Serial.begin(9600);
  Wire.begin();
}

void loop(){

  float celsius = getTemperature();
  Serial.print("Celsius: ");
  Serial.println(celsius);

  float fahrenheit = (1.8 * celsius) + 32;
  Serial.print("Fahrenheit: ");
  Serial.println(fahrenheit);

  delay(200); //just here to slow down the output. You can remove this
}

float getTemperature(){
  Wire.requestFrom(tmp102Address,2); 

  byte MSB = Wire.read();
  byte LSB = Wire.read();

  //it's a 12bit int, using two's compliment for negative
  int TemperatureSum = ((MSB << 8) | LSB) >> 4; 

  float celsius = TemperatureSum*0.0625;
  return celsius;
}
}}}