Create an Arduino Library (Step by Step)

https://www.youtube.com/watch?v=IiZl3p-ZohM

Arduino pin 8 adn Pin 8 as Serial Input and Output

 arduino pin 8 as serial input

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Serial and SoftwareSerial • Wolles Elektronikkiste
The line of code SoftwareSerial mySerial(8, 9); is used in Arduino programming to create a software serial object. It initializes a new serial communication port, but instead of using the standard hardware serial port (0 and 1), it utilizes digital pins 8 and 9 for serial communication. This allows you to use other digital pins for other purposes while still having a serial interface.
Here's a breakdown:

    SoftwareSerial:
    This is a library that enables serial communication on other digital pins of an Arduino board.
    mySerial:
    This is the name you've given to your software serial object. You can use this name to refer to this specific port when sending and receiving data.
    (8, 9):
    These are the two digital pins that will be used for the software serial port. Pin 8 is typically used for the receive (RX) signal, and pin 9 is used for the transmit (TX) signal.

How it works:

    1. Include the library:
    Before using SoftwareSerial, you need to include the SoftwareSerial.h library in your code: #include <SoftwareSerial.h>.

2. Initialize:
The SoftwareSerial mySerial(8, 9); line creates the object and initializes the specified pins for software serial communication.
3. Use the object:
You'll use the mySerial object (e.g., mySerial.begin(9600); to set the baud rate, mySerial.write(...) to send data, and mySerial.available() and mySerial.read() to receive data).
4. Connect:
When using software serial, you'll need to connect the RX pin of the other device (e.g., a Bluetooth module, another Arduino) to pin 8 and the TX pin to pin 9.
5. Baud Rate:
Make sure the baud rate (e.g., 9600, 115200) on both devices is the same for successful communication.
 

Arduino Serial Communication (Jeremy Blum)

 https://www.jeremyblum.com/2011/02/07/arduino-tutorial-6-serial-communication-and-processing/

 

https://forum.arduino.cc/t/how-can-i-control-an-led-via-the-serial-monitor/1052017

 

https://toptechboy.com/arduino-lesson-4-printing-over-the-serial-port/

I2C Arduino

 https://dronebotworkshop.com/i2c-arduino-arduino/

 https://www.circuitbasics.com/how-to-set-up-i2c-communication-for-arduino/

 

 

 

 MASTER

/*
  I2C Master Demo
  i2c-master-demo.ino
  Demonstrate use of I2C bus
  Master sends character and gets reply from Slave
  DroneBot Workshop 2019
  https://dronebotworkshop.com
*/

// Include Arduino Wire library for I2C
#include <Wire.h>

// Define Slave I2C Address
#define SLAVE_ADDR 9

// Define Slave answer size
#define ANSWERSIZE 5

void setup() {

  // Initialize I2C communications as Master
  Wire.begin();
 
  // Setup serial monitor
  Serial.begin(9600);
  Serial.println("I2C Master Demonstration");
}

void loop() {
  delay(50);
  Serial.println("Write data to slave");
 
  // Write a charatre to the Slave
  Wire.beginTransmission(SLAVE_ADDR);
  Wire.write(0);
  Wire.endTransmission();
    
  Serial.println("Receive data");
 
  // Read response from Slave
  // Read back 5 characters
  Wire.requestFrom(SLAVE_ADDR,ANSWERSIZE);
 
  // Add characters to string
  String response = "";
  while (Wire.available()) {
      char b = Wire.read();
      response += b;
  }
 
  // Print to Serial Monitor
  Serial.println(response);
}

 SLAVE

/*
  I2C Slave Demo
  i2c-slave-demo.ino
  Demonstrate use of I2C bus
  Slave receives character from Master and responds
  DroneBot Workshop 2019
  https://dronebotworkshop.com
*/

// Include Arduino Wire library for I2C
#include <Wire.h>

// Define Slave I2C Address
#define SLAVE_ADDR 9

// Define Slave answer size
#define ANSWERSIZE 5

// Define string with response to Master
String answer = "Hello";

void setup() {

  // Initialize I2C communications as Slave
  Wire.begin(SLAVE_ADDR);
 
  // Function to run when data requested from master
  Wire.onRequest(requestEvent);
 
  // Function to run when data received from master
  Wire.onReceive(receiveEvent);
 
  // Setup Serial Monitor
  Serial.begin(9600);
  Serial.println("I2C Slave Demonstration");
}

void receiveEvent() {

  // Read while data received
  while (0 < Wire.available()) {
    byte x = Wire.read();
  }
 
  // Print to Serial Monitor
  Serial.println("Receive event");
}

void requestEvent() {

  // Setup byte variable in the correct size
  byte response[ANSWERSIZE];
 
  // Format answer as array
  for (byte i=0;i<ANSWERSIZE;i++) {
    response[i] = (byte)answer.charAt(i);
  }
 
  // Send response back to Master
  Wire.write(response,sizeof(response));
 
  // Print to Serial Monitor
  Serial.println("Request event");
}

void loop() {

  // Time delay in loop
  delay(50);
}