Connecting OLED SSD1306 SPI display and DS3231 RTC to Arduino Nano

[Dziubym]

I am building a clock using Arduino Nano and OLED SSD1306 SPI display and DS3231 RTC.
My question is regarding connectivity.
When I search for the way each component should be conected I see that

SDA should go to A4
and SCL to A5

The problem I have is that the same connectivity is required for both OLED and RTC. So How to resolve it

Declaration of OLED

#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define OLED_RESET     4 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

Funny enough there is no reset pin on the OLED ITC and the SCL and SDA are connected to A5 and A4
The RTC declaration looks like this

#include <Wire.h>
#include <DS3231.h>
DS3231 clock;
RTCDateTime dt;

Please advice how the wiring shuld look like so both components can work together connected to Arduino Nano

[Nick_Pyner]

I2C is a bus, so several devices can share. They need to have individual addresses. This will be detailed in the respective libraries.

[IoT_hobbyist]

if two devices have two different I2C addresses, they can connect to the same I2C pins of Arduino

[emailarmin]

Hello,

I think you use I2C and not SPI !!

SDA and SCL are I2C signals.

It is very simple :

for OLED you have to determine the DeviceAdresse by a I2C scanner, if you do not know :

#include <Wire.h>
void setup()
{
  Wire.begin();
  Serial.begin(9600);
  Serial.println("\nI2C Scanner");
}

void loop()
{
  byte error, address;
  int nDevices;
  Serial.println("Recherche en cours...");
  nDevices = 0;
  for(address = 1; address < 127; address++ ) 
  {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0)
    {
      Serial.print("Equiment I2C trouve a l'addresse 0x");
      if (address<16) 
        Serial.print("0");
      Serial.print(address,HEX);
      Serial.println("  !");
      nDevices++;
    }
    else if (error==4)
    {
      Serial.print("Erreur inconnue a l'address 0x");
      if (address<16) 
        Serial.print("0");
      Serial.println(address,HEX);
    }    
  }
  if (nDevices == 0)
    Serial.println("Aucun Equipement I2C trouve\n");
  else
    Serial.println("Fini\n");

  delay(5000);           
}

and then you use your oled device with this adress, here an example with the display I use :

#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 32 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     4 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);


void setup() {
  Serial.begin(9600);

  // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3C for 128x32
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }

the adress is : 0x3C

For RTC it is strange, you do not need to define adress, but It works perfectly, so the combined code is like :

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

// rtrc + oled
// ***********
DS3231 clock;
RTCDateTime dt;

// oled
// ****
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     4 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

void setup()
{
  Serial.begin(9600);

  // Initialize DS3231
  Serial.println("Initialize DS3231");;
  clock.begin();

 // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }

 }