Sending 4 analog values from one arduino to another with I2C

Question

I have modded a cheap drone controller to output its joystick values to an Arduino Nano.

I made it to output its 4 pot values using I2C to another Arduino don't ask why. So my problem is that I need to send 4 values but I can send only 1. Help me please.

I don't have a time limit or something so I don't need this quick or now!

I am also using a 16x2 LCD without I2C to show the live values and sometime I want to make a menu there or stuff like that.

I would like if you wrote the code for me but its ok if you cant. Also I'm kind of a noob at arduino programming.

Master(a.k.a the nano in the controller):

int pot1 = A0;
int pot2 = A1;
int pot3 = A2;
int pot4 = A3;

int potValue1 = 0;
int potValue2 = 0;
int potValue3 = 0;
int potValue4 = 0;

int led = 10;
int button = 8;

int lastButtonState;    // the previous state of button
int currentButtonState; // the current state of button

int output1 = A4;
int output2 = A5;
int output3 = A6;
int output4 = A7;

#include <Wire.h>
#include <LiquidCrystal.h> // includes the LiquidCrystal Library

LiquidCrystal lcd(2, 3, 4, 5, 6, 7); // Creates an LC object. Parameters: (rs, enable, d4, d5, d6, d7)

#define SLAVE_ADDR 9

void setup() {
  pinMode(led, OUTPUT);
  pinMode(button, INPUT_PULLUP);

  // Open serial communications and wait for port to open:
  Wire.begin();

  lcd.begin(16, 2);
  lcd.print("   ArduinoTX");
  digitalWrite(led, HIGH);
  delay(600);
  digitalWrite(led, LOW);
  delay(600);
  digitalWrite(led, HIGH);
  delay(600);
  digitalWrite(led, LOW);
  delay(600);
  digitalWrite(led, HIGH);
  delay(600);
  delay(3000);
  lcd.clear();
}

void loop() {
  currentButtonState = digitalRead(button);
  potValue1 = analogRead(pot1);
  potValue2 = analogRead(pot2);
  potValue3 = analogRead(pot3);
  potValue4 = analogRead(pot4);

  int sendValue = map(potValue4, 1, 1023, 1, 255);  //converting to values 255 max
  int sendValue2 = map(potValue3, 1, 1023, 1, 255);
  int sendValue3 = map(potValue2, 1, 1023, 1, 255);
  int sendValue4 = map(potValue1, 1, 1023, 1, 255);

  Wire.beginTransmission(SLAVE_ADDR); //sending only one pot value
  Wire.write(sendValue);
  Wire.endTransmission();

  lastButtonState  = currentButtonState;      // save the last state
  currentButtonState = digitalRead(button); // read new state

  if (lastButtonState == LOW && currentButtonState == LOW) { //dont worry about this
    lcd.print(potValue4);
    lcd.print("        ");
    lcd.print(potValue2);
    delay(delayTime);
    lcd.clear();
    lcd.setCursor(0, 2);
    lcd.print(potValue3);
    lcd.print("        ");
    lcd.print(potValue1);
    delay(delayTime);
    lcd.clear();
  }
}

Slave(or an uno who receives the values):

int rd;
int br;

#include <Wire.h>

#define SLAVE_ADDR 9

void setup() {
  // put your setup code here, to run once:
  Wire.begin(SLAVE_ADDR);
   
  // Function to run when data received from master
  Wire.onReceive(receiveEvent);
 
  // Setup Serial Monitor
  Serial.begin(9600);
}

void receiveEvent() {
  // read one character from the I2C
  rd = Wire.read();
  Serial.println(rd);  
}

void loop() {
  delay(50);
}

Thanks!

Answer 1

Why are you limited to sending one value? You can have multiple Wire.write() calls in one transmission.

The slave side just needs to know to expect multiple values in order to accommodate. The best way to do this would be to read in values as long as the master is sending them (check out https://www.arduino.cc/en/Reference/WireRead).

Then your master changes from

Wire.beginTransmission(SLAVE_ADDR);
Wire.write(sendValue);
Wire.endTransmission();

to

Wire.beginTransmission(SLAVE_ADDR);
Wire.write(sendValue);
Wire.write(sendValue2);
Wire.write(sendValue3);
Wire.write(sendValue4);
Wire.endTransmission();

And the slave receiveEvent() becomes

int receiveValue;
int receiveValue2;
int receiveValue3;
int receiveValue4;  
int index = 0;
while(Wire.available()){
    if(index == 0){ receiveValue = Wire.read(); }
    else if(index == 1) {receiveValue2 = Wire.read(); }
    else if(index == 2) {receiveValue3 = Wire.read(); }
    else if(index == 3) {receiveValue4 = Wire.read(); }
    index++;
}

I would also consider using arrays as a way to clean up some of your variables, but making the above changes should accomplish what you want if not as cleanly.