Using a I2C LCD while also using slave ardunio

Projects Networking, Protocols, and Devices
1

This is the setup I have, and it works in Tinkercad but when I build it the LCD does not do anything. If the slave uno is not connected, the LCD will function but as soon as I connect SLC and SDA to A4 and A5 it stops, even without powering the other slave UNO.

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MASTER CODE:


#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

const byte numRows = 4; //number of rows on the keypad
const byte numCols = 4; //number of columns on the keypad

//keymap defines the key pressed according to the row and columns just as appears on the keypad
char keymap[numRows][numCols] =
{
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

String room = "";

//Code that shows the the keypad connections to the arduino terminals
byte rowPins[numRows] = {9, 8, 7, 6}; //Rows 0 to 3
byte colPins[numCols] = {5, 4, 3, 2}; //Columns 0 to 3

//initializes an instance of the Keypad class
Keypad myKeypad = Keypad(makeKeymap(keymap), rowPins, colPins, numRows, numCols);

void setup()
{
  Serial.begin(9600);
  lcd.backlight();
  lcd.init();
  lcd.print("Enter Room");
  Wire.begin(); 
  pinMode(LED_BUILTIN, OUTPUT);



}

//If key is pressed, this key is stored in 'keypressed' variable
//If key is not equal to 'NO_KEY', then this key is printed out
//if count=17, then count is reset back to 0 (this means no key is pressed during the whole keypad scan process
void loop()
{
  char pressedKey = myKeypad.getKey();
  switch (pressedKey) {

    case '#':
      lcd.clear();
      Serial.println("Enter : ");
      Serial.println(room);
      lcd.print("Enter: " + room);
      transmit();
      room = "";
      break;
    case '*':
      Serial.println("Reset");
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Reset");
      delay(1000);
      lcd.clear();
      room = "";
      break;

    default:
      if (pressedKey == NO_KEY) break;
      digitalWrite(LED_BUILTIN, HIGH);
	  delay(200);
  	  digitalWrite(LED_BUILTIN, LOW);


      if (room.length() >= 4) break;
      if (room.length() == 0 && !(pressedKey == ('A') || pressedKey == ('B') || pressedKey == ('C') || pressedKey == ('D') )) break;
      if (room.length() >= 1 && (pressedKey == ('A') || pressedKey == ('B') || pressedKey == ('C') || pressedKey == ('D') )) break;

      room += (pressedKey);
      Serial.println(room);
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print(room);

      break;
  }

}

void transmit(){

  int x = room.length();
  for(int y = 0; y<x; y++){
  Wire.beginTransmission(9); // transmit to device #9
  Wire.write(room[y]);
  Wire.endTransmission();
  }
  
}

SLAVE CODE:

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>

char x;
String room = "";

void setup() {
  // Define the LED pin as Output
  pinMode(13, OUTPUT);
  pinMode(12, OUTPUT);

  // Start the I2C Bus as Slave on address 9
  Wire.begin(9); 
  // Attach a function to trigger when something is received.
  Wire.onReceive(receiveEvent);
  Serial.begin(9600);

}

void receiveEvent(int bytes) {
  
  x = Wire.read();
  Serial.println("Recieved");
  room += x;
  Serial.println(room);
  
      // read one character from the I2C
}
void loop() {
   digitalWrite(13, HIGH);
   delay(200);
   digitalWrite(13, LOW);
     delay(200);

  
  //If value received is 0 blink LED for 200 ms
  if(room == "A123"){
    resetRoom();
    

 
  }
  if(room == "A321"){
    resetRoom();
  digitalWrite(12, HIGH);
    delay(200);
    digitalWrite(12, LOW);
  
  }

}


void resetRoom(){
room = "";
}

Any recommendations?

2

Do you think that connecting the pins to the second Arduino just might be trying to power the second Arduino through your pin connections?

3

powering the slave ardunio made it work. thanks!

4

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