Bluetooth sending values from two joysticks

Question

Is there any good way of sending values from two joysticks from arduino A to arduino B? I tried sending using if statements, so if the Y- or X-axis' value changed then it would send that, but the servo motor on Arduino B went a little bit crazy.

Here's what I've done so far:

//Master Code
void loop()
{
      yVal = analogRead(yAxis);   // read the value of the Right Joystick (value between 0 and 1023)
      yMap = map(yVal, 0, 1023, 0, 255);
      xVal = analogRead(xAxis);     // read the value of the left Joystick (value between 0 and 1023)
      xMap = map(xVal, 0, 1023, 0, 110);

  if(Serial.available() && !(xVal > 505 && xVal < 510)){
      Serial.print('X');
      delay(10);
      Serial.write(xMap);
      }
  if(Serial.available() && !(yVal > 500 && yVal < 520)){
      Serial.print('Y');
      delay(10);
      Serial.write(yMap);

    }
    delay(10);
}

And the Slave code:

//Slave code
void loop(){
  while(Serial.available())
  {
    c = Serial.read();
    delay(5);
    val = Serial.read();
    if(c == 'X'){
        digitalWrite(13, LOW);
        myServo.write(val);
    }else if(c == 'Y'){
        digitalWrite(13, HIGH);
    }
    }

}

Edit: I was thinking that maybe I should do something like a start and stop bit for X and Y?

Edit2: I wrote an if statement in Arduino B because it was reading the value -1, I don't know why, but after the if statement the servo motor hasn't been going crazy and the program works now. I still would like to know if I can do this in a better way. Thanks in advance!

Answer 1

Arduino A

You can read the values from two joysticks as normal and send it like this. This method ensures of no data loss. Ensure that you read the values and store them in appropriate variables and then send it over serial.

// Setting Sensor pins
const int potPin = A0;
const int pot1Pin = A1;




// Creating variables
uint8_t pot;
uint8_t pot1;

void setup() {
// Declearing the pinModes' for sensors
  pinMode(potPin, INPUT);
  pinMode(pot1Pin, INPUT);
// Begining Serial Communication
  Serial.begin(9600);

}

void loop() {
// reading from the sensors
  pot = map(analogRead(potPin),0 ,1023, 0, 255);
  pot1 = map(analogRead(pot1Pin),0 ,1023, 0, 255);  

//Packing the Serial message
  Serial.print("U*"); //A header
  Serial.print("A");  //a token to indicate the message payload
  Serial.print(pot);
  Serial.println("");  

  Serial.print("U*"); //A header
  Serial.print("B");  //a token to indicate the message payload
  Serial.print(pot1);
  Serial.println("");  


}

Arduino B

After the data are packed and sent over the serial. You need to unpack it with the other Arduino/device

The code will look like this:

String data; //Store each line of Serial communication
String pot1String = "0", pot2String = "0";
float pot1, pot2;
void setup() 
{
  //initialize Serial communication 
  Serial.begin(9600);
  //read first package
  if (Serial.available() > 0)
  {
    data = Serial.readStringUntil('\n');
  }
  //Disregard the first reading
  data = "0";
}

void loop() {
  //start reading from serial
  if (Serial.available() > 0)
  {
    data = Serial.readStringUntil('\n');  
  }
  String payload = ""; 
  if (data != "0")
  {
    int offset = data.indexOf("U*"); //This is the header (0x552A)
    if (offset >= 0)
    {
      payload = data.substring(offset + 3, data.indexOf('\n'));
      char value = data.charAt (offset + 2);
      switch (value)
      {
        case 'A':
          pot1String = payload;
          break;
        case 'B':
          pot2String = payload;
          break;
      //Add more case as the project grow
      }
    }
  }
  //convert strings to float
  pot1 = pot1String.toFloat();
  pot2 = pot2String.toFloat();

// Continue with the rest of your project

}

• Make sure to use the same baud rate in both sketches

Hope this helped. Ask me if you have farther questions

Answer 2

When using the ADC to control servos I get much better results when I process the ADC values through an exponential smoothing function:

There is less jitter. However there is more lag. You can tune the function by changing alpha between 1 (no history, effectively no smoothing at all) to 0 (no new data is averaged in, effectively not changing). Pick 0.5 to start with. If there is too much jitter pick smaller numbers until the jitter is reduced and the lag is still tolerable.