Integrating Arduino and Processing - button counter

问题

I am looking to integrate Arduino controls and Processing Interface. In my Arduino code, there are three buttons attached to pin a1, a0 and d0 (all digitalRead).

int x;// assigned to A0 input
int y;// assigned to A1 input
int z; //assigned to D0 input
int votes[3]={0,0,0};

void setup() {
  // initialize the serial communication
  Serial.begin(9600);

  while(!Serial);
}

void loop() {
  // first we need to read the values from the BUTTONS

  x = digitalRead(A0);

  y = digitalRead(A1);

  z = digitalRead(0);

  if(digitalRead(A0) == HIGH) 
    {
    Serial.print("cat1 ");                  
    Serial.print(votes[0]=votes[0]+1);
    Serial.print("\n");
    }
   else if(digitalRead(A1) == HIGH)
    {
    Serial.print("cat2 ");
    Serial.print(votes[1]=votes[1]+1);
      Serial.print("\n");
    }
   else if(digitalRead(0) == HIGH) 
    {
    Serial.print("cat3 ");
    Serial.print(votes[2]=votes[2]+1);
    Serial.print("\n");
    }

    delay(200);
}

I would like the counter to increment every time the button is pressed and display in processing as a bar graph. Whenever the button is pressed, the bar graph goes up by some amount. In this case I want one of the three lines (associated to three buttons) to draw, if pressed.

The processing code is below:

import processing.serial.*;

// Serial Port variables
Serial myPort;
String buff = "";
String buff1 = "";
String buff2 = "";
int index = 0;
int NEWLINE = 10;
// Store the last 256 values from the sensors so we can draw them.
int[] valuesx = new int[256];
int[] valuesy = new int[256];
int[] valuesz = new int[256];

void setup()
{ 
  // set size of the window 
  size(512, 512);
  // turn on anti-aliasing, this makes things look smoother 
  smooth();

  println(Serial.list()); // use this to determine which serial port is your Arduino
  myPort = new Serial(this, Serial.list()[0], 9600);
  myPort.bufferUntil('\n');
}

// draw() happens every frame of the sketch. This is where all the calculations are made.
// When draw() is finished executing, it executes again, over and over.
void draw() {
  // set the background to purple
  background(87, 36, 124);
  // set stroke weight(thickness of the line) to 5 pixels
  strokeWeight(5);

  for (int i = 0; i < 255; i++) {

    stroke(247, i);
    // draw the line (x1, y1, x2, y2)
    line(1, valuesx[i], 1, valuesx[i + 1]);
    line(5, valuesy[i], 5, valuesy[i + 1]);
    line(10, valuesz[i], 10, valuesz[i + 1]);
  }

  // Check the Serial port for incoming data
  while (myPort.available () > 0) {
    // if there is data waiting...
    // execute serialEvent() function. Look below to see how SerialEvent works.
    serialEvent(myPort.read());
  }
}

// serialEvent controls how incoming serial data from the Arduino module is handled
void serialEvent(int serial)
{
  if (serial != NEWLINE) {
    // Store all the characters on the line.
    buff += char(serial);
  } 
  else {
    // The end of each line is marked by two characters, a carriage
    // return and a newline.  We're here because we've gotten a newline,
    // but we still need to strip off the carriage return.
    buff = buff.substring(0, buff.length()-1);
    index = buff.indexOf(",");
    buff1 = buff.substring(0, index);
    buff2 = buff.substring(index+1, buff.length());

    // Parse the String into an integer.  We divide by 4 because
    // analog inputs go from 0 to 1023 while colors in Processing
    // only go from 0 to 255.
    int x = Integer.parseInt(buff1)/2;
    int y = Integer.parseInt(buff2)/2;

    // Clear the value of "buff"
    buff = "";

    // Shift over the existing values to make room for the new one.
    for (int i = 0; i < 255; i++)
    {
      valuesx[i] = valuesx[i + 1];
      valuesy[i] = valuesy[i + 1];
    }

    // Add the received value to the array.
    valuesx[255] = x;
    valuesy[255] = y;
  }
}

Unfortunately, here's the error that I get when I press a button.

回答1:

It looks like you're expecting buff to contain a comma, but it doesn't.

When you call indexOf(","), it returns -1 to indicate that no comma was found:

index = buff.indexOf(",");

Then when you call substring(), you're passing in -1 as the index, which isn't a valid parameter:

buff1 = buff.substring(0, index);

That's what's causing the error. Now your next question will be: why doesn't buff contain a comma?

And the answer to that is going to depend on what you're expecting from your Arduino. Try printing out the value of buff to see what it is.

I don't know much about Arduino, but I don't see anywhere in that code that prints a comma.

来源：https://stackoverflow.com/questions/38491993/integrating-arduino-and-processing-button-counter