[Processing] PM2008 packet to CSV

packet.java

import java.util.ArrayList;

class Packet {
  static final int PACKET_STX = 0xAB;
  static final int PACKET_ETX = 0x7D;

  static final int PACKET_CMD_GET_PM2008 = 0;

  static final int PACKET_POS_STX = 0;
  static final int PACKET_POS_LEN = 1;
  static final int PACKET_POS_CMD = 2;
  static final int PACKET_POS_DAT = 3;

  private ArrayList<Integer> buffer = new ArrayList<Integer>();

  Packet() {
  }

  Packet(int[] rxBuffer) {
    for (int b : rxBuffer) {
      buffer.add(b);
    }
  }

  private void clear() {
    buffer.clear();
  }

  public void generate(int cmd, int[] data) {
    clear();

    buffer.add(PACKET_STX);
    // (STX), (LEN), CMD, D.., CS, ETX
    buffer.add(data.length + 3);
    buffer.add(cmd);

    for (int b : data) {
      buffer.add(b);
    }

    int cs = buffer.get(PACKET_POS_STX);

    for (int i=1; i<buffer.size(); i++) {
      cs ^= buffer.get(i);
    }

    buffer.add(cs);
    buffer.add(PACKET_ETX);
  }

  public boolean check() {
    if (buffer.get(PACKET_POS_STX) != PACKET_STX) {
      return false;
    }

    if (buffer.get(buffer.size() -1) != PACKET_ETX) {
      return false;
    }

    if (buffer.get(PACKET_POS_LEN) + 2 != buffer.size()) {
      return false;
    }

    switch (buffer.get(PACKET_POS_CMD)) {
    case PACKET_CMD_GET_PM2008:
      {
        break;
      }
    default:
      return false;
    }

    int cs = buffer.get(PACKET_POS_STX);

    for (int i=1; i<buffer.size() - 2; i++) {
      cs ^= buffer.get(i);
    }

    if (cs != buffer.get(buffer.size() -2)) {
      return false;
    }

    return true;
  }

  public int getDataLength() {
    return buffer.size() - 5;
  }

  public int getCmd() {
    return buffer.get(PACKET_POS_CMD);
  }

  public int[] getData() {
    int dataLength = getDataLength();

    if (dataLength == 0) {
      return new int[0];
    }

    int[] result = new int [dataLength];

    for (int i=0; i<dataLength; i++) {
      result[i] = buffer.get(PACKET_POS_DAT +i);
    }

    return result;
  }

  public byte[] getBytes() {
    byte[] bytes = new byte[buffer.size()];

    for (int i=0; i<buffer.size(); i++) {
      bytes[i] = buffer.get(i).byteValue();
    }
    
    return bytes;
  }
}

pm2008_packet_logger.pde

import processing.serial.*;

PrintWriter output;
Serial myPort;

ArrayList<Integer> rxBuffer = new ArrayList<Integer>();
int idxBuffer = 0;
int rearLength = 0;

Packet txPacket = new Packet();

void setup() {
  //printArray(Serial.list());
  // "/dev/tty.usbmodem113201"

  Packet packet = new Packet();
  // packet.check();
  packet.generate(Packet.PACKET_CMD_GET_PM2008, new int[0]);

  myPort = new Serial(this, "/dev/tty.usbmodem113201", 9600);
  
  output = createWriter("data.csv");
  // PM 1.0 (GRIMM)/PM 2.5 (GRIMM)/PM 10 (GRIMM)/
  // PM 1.0 (TSI)/PM 2.5 (TSI)/PM 10 (TSI)/
  // 0.3 um/0.5 um/1 um/2.5 um/5 um/10 um

  output.println("PM 1.0 (GRIMM),PM 2.5 (GRIMM),PM 10 (GRIMM),PM 1.0 (TSI),PM 2.5 (TSI),PM 10 (TSI),0.3 um,0.5 um,1 um,2.5 um,5 um,10 um");
  
  frameRate(1);
  
  txPacket.generate(Packet.PACKET_CMD_GET_PM2008, new int[0]);
}

void draw() {
  myPort.write(txPacket.getBytes());
}

void serialEvent(Serial port) {
  while (port.available() > 0) {
    int b = port.read();

    if (b < 0) {
      continue;
    }

    switch(idxBuffer) {
    case 0: // STX
      {
        if (b != Packet.PACKET_STX) {
          idxBuffer = 0;
          rxBuffer.clear();
          break;
        }

        rxBuffer.add(b);
        ++idxBuffer;
        break;
      }
    case 1: // LEN
      {
        if (b < 3) {
          idxBuffer = 0;
          rxBuffer.clear();
          break;
        }

        rxBuffer.add(b);
        ++idxBuffer;
        rearLength = b;
        break;
      }
    case 2: // CMD
      {
        if (b != Packet.PACKET_CMD_GET_PM2008) {
          idxBuffer = 0;
          rxBuffer.clear();
          break;
        }

        rxBuffer.add(b);
        ++idxBuffer;
        break;
      }
    default:
      {
        rxBuffer.add(b);
        ++idxBuffer;

        if (idxBuffer >= rearLength + 2) {
          int[] bytes = rxBuffer.stream().mapToInt(i -> i).toArray();

          idxBuffer = 0;
          rxBuffer.clear();

          if (b != Packet.PACKET_ETX) {
            break;
          }

          Packet packet = new Packet(bytes);

          if (!packet.check())
          {
            break;
          }

          int dataLength = packet.getDataLength();
          int cmd = packet.getCmd();

          int[] data = packet.getData();

          switch(cmd) {
          case Packet.PACKET_CMD_GET_PM2008:
            {
              if (dataLength != 25) {
                break;
              }

              if (data[0] != 0) {
                break;
              }
              
              for(int i=0; i<12; i++) {
                output.print((data[2*i+1] + (data[2*(i+1)] << 8)));  
                
                if (i <11){
                  output.print(",");
                } else {
                  output.println();  
                }
              }
              
              println("added!!");
              
              break;
            }
          default:
            break;
          }
        }
        break;
      }
    }
  }
}

void keyPressed() {
  output.flush();
  output.close();
  exit();
}