Arduino Tutorial

By LiterallyTheOne

7: I2C: Part 1

Introduction

• Previous tutorial: Interrupt
• This tutorial: I2C

I2C Communication

• Inter-Integrated Circuit
• 2 Wire
• Short-distance

I2C Pins

• SDA: Serial Data
• SCL: Serial Clock

Master and Slave

• Master: 1
• Slave: multiple
• We can connect multiple components to the same pins

Master's privileges

• Controls the clock on SCL
• Decides that if it wants to communicate with slaves

Communication structure

I2C pins in Arduino Uno

Wire

• Library to control I2C Communication in Arduino
• Include Wire:

#include <Wire.h>

• Initilize Wire:

Wire.begin();

Different communication with an slave

• Read
• Write

Write

// start the communication in order to write
// with the slave with the address of `addr`
Wire.beginTransmission(addr);   
Wire.write(data);               // write data
Wire.endTransmission();         // finish transmission

Read

// start a read communication with the slave
// with the address of `addr` and read `number` bytes
Wire.requestFrom(addr, number);
Wire.read();                    // read bytes

Connect a Clock to an Arduino

• DS1307: Micro/Peripherals/DS1307

Code to scan

#include <Arduino.h>
#include <Wire.h>

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

void loop()
{
  for (int i = 0; i < 127; i++)
  {
    Wire.beginTransmission(i);
    if (Wire.endTransmission() == 0)
    {
      Serial.println("Device found at address: 0x" + String(i, HEX));
    }
  }
  delay(2000);
}

Connect OLED

• SSD1306: Outputs/Displays/SSD1306

Clock: DS1307

• Real-Time Clock (RTC) integrated circuit
• keeps track of the current time and date
• Battery

DS1307 registers

Way that it stores data

• Storing: 0x22 -> 22
• Not 2*16+2

DS1307: Define Clock Adress

#define CLOCK_ADDRESS 0x68

DS1307: Jump to the minutes register

Wire.beginTransmission(CLOCK_ADDRESS);
Wire.write(0x01); // Address that we want to jump to
Wire.endTransmission();

DS1307: Request bytes

Wire.requestFrom(CLOCK_ADDRESS, 2);

byte minutes = Wire.read();
byte hours = Wire.read();

Serial.println("Minutes: " + String(minutes, HEX));
Serial.println("Hours: " + String(hours, HEX));

delay(1000);

DS1307: Read output

DS1307: Read all 7 registers

DS1307: Convert decimal to hex in order to write

• We want to write: 25
• If we send 25
  • It would store: 0x19
  • 25/16=1, 25%16=9
• We should send 0x25
  • which is: 37
  • 2*16+5=37

DS1307: Code for converting

byte minutes_to_write = 25;
// convert 25 to 0x25
minutes_to_write = (minutes_to_write / 10) * 16 + minutes_to_write % 10;

DS1307: Code for writing

// Write minutes
Wire.beginTransmission(CLOCK_ADDRESS);
Wire.write(0x01); // Address that we want to jump to
Wire.write(minutes_to_write);
Wire.endTransmission();

DS1307: Write output

OLED: SSD1306

• OLED (Organic Light Emitting Diode)
• Graphic display modules

AdaFruit

• Library to control graphics
• Add to platfomIO

lib_deps =
    Adafruit SSD1306
    Adafruit GFX Library

• Include

#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

SSD1306: global variables

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire);

SSD1306: setup

if (!display.begin(SSD1306_SWITCHCAPVCC, SSD1306_ADDRESS))
{
Serial.println("SSD1306 failed!");
for (;;)
  ;
}

display.setTextSize(1);
display.setTextColor(WHITE, BLACK);

SSD1306: display

display.clearDisplay();
display.setCursor(0, 0);

display.print("Hello World!");
display.display();

SSD1306: Show the clock

OLED ball

OLED ball line

Link to the tutorial and materials