0.91 "OLED"

I2C pin definition

With I2C communication, it is inevitably involved in the definition of the pin, and the pin of the ESP32 used by I2C is reflected in the program. The specific pins of the ESP32 can be set for I2C communication using the setPins () or begin () function in Wire.h.

    //call setPins() first, so that begin() can be called without arguments from libraries
    bool setPins(int sda, int scl);
    
    bool begin(int sda=-1, int scl=-1, uint32_t frequency=0); // returns true, if successful init of i2c bus
      // calling will attemp to recover hung bus

The specific implementation of the setPins () and begin () functions can be seen in Wire.cpp:

bool TwoWire::setPins(int sdaPin, int sclPin)
{
    if(i2c) {
        log_e("can not set pins if begin was already called");
        return false;
    }
    sda = sdaPin;
    scl = sclPin;
    return true;
}

bool TwoWire::begin(int sdaPin, int sclPin, uint32_t frequency)
{
    if(sdaPin < 0) { // default param passed
        if(num == 0) {
            if(sda==-1) {
                sdaPin = SDA;    //use Default Pin
            } else {
                sdaPin = sda;    // reuse prior pin
            }
        } else {
            if(sda==-1) {
                log_e("no Default SDA Pin for Second Peripheral");
                return false; //no Default pin for Second Peripheral
            } else {
                sdaPin = sda;    // reuse prior pin
            }
        }
    }

    if(sclPin < 0) { // default param passed
        if(num == 0) {
            if(scl == -1) {
                sclPin = SCL;    // use Default pin
            } else {
                sclPin = scl;    // reuse prior pin
            }
        } else {
            if(scl == -1) {
                log_e("no Default SCL Pin for Second Peripheral");
                return false; //no Default pin for Second Peripheral
            } else {
                sclPin = scl;    // reuse prior pin
            }
        }
    }

    sda = sdaPin;
    scl = sclPin;
    i2c = i2cInit(num, sdaPin, sclPin, frequency);
    if(!i2c) {
        return false;
    }

    flush();
    return true;

}

Arduino program

//  Author: Nick
//  Date:22 Sep,2021

//  This library is free software; you can redistribute it and/or
//  modify it under the terms of the GNU Lesser General Public
//  License as published by the Free Software Foundation; either
//  version 2.1 of the License, or (at your option) any later version.
//
//  This library is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//  Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public
//  License along with this library; if not, write to the Free Software
//  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

// ESP32 Arduino Driver 0.91 "OLED
//NODEMCU-32 V1.2
//Arduino V1.8.16
// Reference link:
// Non-SDA and SCL pin settings: http://www.taichi-maker.com/homepage/reference-index/display-reference-index/ARDUINO-OLED-APPLICATION/
// SDA and SCL are defined in ware.begin (): https://blog.csdn.net/qq_42805977/Article/details/107765966

#include <Wire.h>

// introduce the library required to drive OLED0.91
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // Set OLED Width, Unit: Pixels
#define SCREEN_HEIGHT 32 // Set OLED height, unit: pixel

// Customize the reset pin, although the tutorial is not used, but it is necessary for the Adafrouit_ssd1306 library file.
#define OLED_RESET 4
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

void setup()
{
  Wire.begin(/*SDA*/17,/*SCL*/16);
  // Initialize OLED and set its IIC address to 0x3c
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
}

void loop()
{
  words_display();
  display.display();
}

void words_display()
{
  // Clear the screen
  display.clearDisplay();

  // Set the font color, white visible
  display.setTextColor(WHITE);

  // Set the font size
  display.setTextSize(1.5);

  / / Set the cursor position
  display.setCursor(0, 0);
  display.print("0.91 OLED");

  display.setCursor(0, 10);
  display.print("Run time: ");
  // Print the number of seconds since the development board reset:
  display.print(millis() / 1000);
  display.print(" s");

  display.setCursor(0, 20);
  display.print("Author: ");
  display.print("Nick");
}

Reference link

1) Describe the overall implementation of ideas and libraries to add precautions, not illustrated by SDA and SCL pins set:http://www.taichi-maker.com/homepage/reference-index/display-reference-index/arduino-oled-application/

2) Describe the SDA and SCL pin settings, that is, SDA and SCL are defined in ware.begin ():Remember adafrouit_ssd1306 uses custom I2C pins

void setup() 
{
  Wire.begin(/*SDA*/12,/*SCL*/14);
}