将数组数据从处理发送到Arduino

Question

I successfully managed to send a single integer from processing to Arduino but now I want to send an array of three integers and I can't get it working. I want to create a buzzer feedback with Arduino which processing will control which buzzer to activate. For example, the data send from processing should be [1,0,1] meaning sensor 1 and 3 should start working. The buzzers should be able to be activated simultaneously in case that [1,1,1] goes through.

This is the code I have so far: I am trying to understand what data is being sent back to Arduino to know how to use it and I keep getting either a null value or a random integer.

I'm trying to learn how to do this so apologies if the code is bad.

Arduino

void setup(){
  Serial.begin(9600); // Start serial communication at 9600 bps
}

void loop(){
  if (Serial.available()){ 
     const char data = Serial.read();
     char noteBuzzer[] = {data}; 
  for (int i = 0 ; i < sizeof(noteBuzzer); i++) {
  }
   Serial.print(noteBuzzer[1]);
  }
 }

Processing

import processing.serial.*;
String notes[];
String tempo[];
Serial myPort;  
String val;

void setup(){
  size(200,200); 
  String portName = Serial.list()[0]; 
  myPort = new Serial(this, portName, 9600);
  notes = loadStrings("data/notes.txt");
 tempo = loadStrings("data/tempo.txt");
}

 void draw() {
    if (keyPressed == true) 
     {                          
      if (key == '1') {
         println("Start"); 
        readNotes();
      } 
    }
 }

 void readNotes(){
   for (int i = 0 ; i < notes.length; i++) {
   println(notes[i]);
   //println(tempo[i]);
   myPort.write(notes[i]);
   delay(int(tempo[i])); //this will be the tempo? 
    if ( myPort.available() > 0) 
     {  
      val = myPort.readStringUntil('\n');         
       println("Arduino",val); 
     } 
 }

}

Answer 1

If you're data is an array that always has 3 items and each of those items are always either 1 or 0 (bits), you could store that whole data in a single byte (and still have 5 more bits to spare). Sending and receiving a byte is pretty simple with Arduino.

Here's a basic sketch that shows you how to flip 3 bits in a single byte:

// the state as a byte
byte buzzerState = 0B000;

void setup(){
  textFont(createFont("Courier New",18),18);
}

void draw(){
  background(0);
  text("DEC: " + buzzerState + 
     "\nBIN:" + binary(buzzerState,3),10,40);
}

void keyPressed(){
  if(key == '1'){
    buzzerState = flipBit(buzzerState,0);
  }
  if(key == '2'){
    buzzerState = flipBit(buzzerState,1);
  }
  if(key == '3'){
    buzzerState = flipBit(buzzerState,2);
  }
}

// flips a bit at a given index within a byte and returns updated byte
byte flipBit(byte state,int index){
  int bit = getBitAt(state,index);
  int bitFlipped = 1 - bit;
  return setBitAt(state,index,bitFlipped);
}
// returns the integer value of a bit within a byte at the desired index
int getBitAt(byte b,int index){
  index = constrain(index,0,7);
  return b >> index & 1;
}
// sets an individual bit at a desired index on or off (value) and returns the updated byte
byte setBitAt(byte b,int index, int value){
  index = constrain(index,0,7);
  value = constrain(value,0,1);

  if(value == 1) b |= (1 << (index));
  else           b &= ~(1 << (index));

  return b;
}

Use keys '1','2' and '3' to flip the bits.

Note that in keypress we're always updating the same byte. The text will display the decimal value first and the binary value bellow.

This is the most efficient way to send your data and the simplest in terms of serial communication. On the Arduino side you can simply use bitRead() on the byte you get from Serial.read() . For more on binary/bits/bytes be sure to read the BitMath Arduino tutorial . Binary may seem intimidating at first, but it's really not that bad once you practice a bit and it's totally worth knowing.

Here's an updated version of the code above that sends the byte to Arduino on the first available serial port (be sure to change Serial.list()[0] with what makes sense for your setup and press 's' to send an update to Arduino:

import processing.serial.*;

// the state as a byte
byte buzzerState = 0B000;

Serial port;

void setup(){
  textFont(createFont("Courier New",18),18);

  try{
    port = new Serial(this,Serial.list()[0],9600);
  }catch(Exception e){
    e.printStackTrace();
  }
}

void draw(){
  background(0);
  text("DEC: " + buzzerState + 
     "\nBIN:" + binary(buzzerState,3),10,40);
}

void keyPressed(){
  if(key == '1'){
    buzzerState = flipBit(buzzerState,0);
  }
  if(key == '2'){
    buzzerState = flipBit(buzzerState,1);
  }
  if(key == '3'){
    buzzerState = flipBit(buzzerState,2);
  }
  if(key == 's'){
    if(port != null){
      port.write(buzzerState);
    }else{
      println("serial port is not open: check port name and cable connection");
    }
  }
}

// flips a bit at a given index within a byte and returns updated byte
byte flipBit(byte state,int index){
  int bit = getBitAt(state,index);
  int bitFlipped = 1 - bit;
  return setBitAt(state,index,bitFlipped);
}
// returns the integer value of a bit within a byte at the desired index
int getBitAt(byte b,int index){
  index = constrain(index,0,7);
  return b >> index & 1;
}
// sets an individual bit at a desired index on or off (value) and returns the updated byte
byte setBitAt(byte b,int index, int value){
  index = constrain(index,0,7);
  value = constrain(value,0,1);

  if(value == 1) b |= (1 << (index));
  else           b &= ~(1 << (index));

  return b;
}

And here's a super basic Arduino sketch:

byte buzzerState;

void setup() {
  Serial.begin(9600);

  //test LEDs setup
  pinMode(10,OUTPUT);
  pinMode(11,OUTPUT);
  pinMode(12,OUTPUT);
}

void loop() {
  if(Serial.available() > 0){
    buzzerState = Serial.read();

    bool bit0   = bitRead(buzzerState,0);
    bool bit1   = bitRead(buzzerState,1);
    bool bit2   = bitRead(buzzerState,2);

    //test LEDs update
    digitalWrite(10,bit0);
    digitalWrite(11,bit1);
    digitalWrite(12,bit2);

  }  
}

If you connect 3 LEDs to pins 10,11,12 you should them toggle as you press keys '1','2','3' then 's' in Processing

One way around binary in Processing could be using a String representation of your data (eg "00000101" for [1,0,1] ) and unbinary() to convert that String to an integer value you can write to serial, but it will be a bit annoying to getting and setting a character at an index (and potentially parsing that char to it's integer value and back)

When you need to send more than a byte things get a bit more complicated as you need to handle data corruption/interruptions, etc. In these situations it's best to setup/design a communication protocol based on your needs and this isn't easy if you're just getting started with Arduino, but not impossible either. Here 's an example, there are many more online.

One quick and dirty thing you could try is sending that data as string terminated by a new line character ( \\n ) which you could buffer until in Arduino then read 4 bytes at a time, discarding the \\n when parsing:

eg sending "101\\n" from Processing, representing [1,0,1] then on the Arduino side use Serial.readStringUntil('\\n') and a combination of charAt() and toInt() to access each integer within that that string.

Here's an example Processing sketch:

import processing.serial.*;

// the state as a byte
String buzzerState = "010\n";

Serial port;

void setup(){
  textFont(createFont("Courier New",18),18);

  try{
    port = new Serial(this,Serial.list()[0],9600);
  }catch(Exception e){
    e.printStackTrace();
  }

}

void draw(){
  background(0);
  text(buzzerState,30,50);
}

void keyPressed(){
  if(key == '1'){
    buzzerState = flipBit(buzzerState,0);
  }
  if(key == '2'){
    buzzerState = flipBit(buzzerState,1);
  }
  if(key == '3'){
    buzzerState = flipBit(buzzerState,2);
  }
  if(key == 's'){
    if(port != null){
      port.write(buzzerState);

    }else{
      println("serial port is not open: check port name and cable connection");
    }
  }
}

String flipBit(String state,int index){
  index = constrain(index,0,2);
  // parse integer from string
  int bitAtIndex = Integer.parseInt(state.substring(index,index+1));
  // return new string concatenating the prefix (if any), the flipped bit (1 - bit) and the suffix
  return state = (index > 0 ? state.substring(0,index) : "") + (1 - bitAtIndex) + state.substring(index+1);
}

And an Arduino one based on Arduino > File > Examples > 04.Communication > SerialEvent :

/*
  Serial Event example

 When new serial data arrives, this sketch adds it to a String.
 When a newline is received, the loop prints the string and
 clears it.

 A good test for this is to try it with a GPS receiver
 that sends out NMEA 0183 sentences.

 Created 9 May 2011
 by Tom Igoe

 This example code is in the public domain.

 http://www.arduino.cc/en/Tutorial/SerialEvent

 */

String inputString = "";         // a string to hold incoming data
boolean stringComplete = false;  // whether the string is complete

void setup() {
  // initialize serial:
  Serial.begin(9600);
  // reserve 200 bytes for the inputString:
  inputString.reserve(200);

  // test LEDs setup
  pinMode(10,OUTPUT);
  pinMode(11,OUTPUT);
  pinMode(12,OUTPUT);
}

void loop() {
  // print the string when a newline arrives:
  if (stringComplete) {
    Serial.println(inputString);
    // process string
    bool bit0   = inputString.charAt(2) == '1';
    bool bit1   = inputString.charAt(1) == '1';
    bool bit2   = inputString.charAt(0) == '1';

    //test LEDs update
    digitalWrite(10,bit0);
    digitalWrite(11,bit1);
    digitalWrite(12,bit2);


    // clear the string:
    inputString = "";
    stringComplete = false;
  }
}

/*
  SerialEvent occurs whenever a new data comes in the
 hardware serial RX.  This routine is run between each
 time loop() runs, so using delay inside loop can delay
 response.  Multiple bytes of data may be available.
 */
void serialEvent() {
  while (Serial.available()) {
    // get the new byte:
    char inChar = (char)Serial.read();
    // add it to the inputString:
    inputString += inChar;
    // if the incoming character is a newline, set a flag
    // so the main loop can do something about it:
    if (inChar == '\n') {
      stringComplete = true;
    }
  }
}

Note this is more prone to error and used 4 times as much data as the the single byte option.