Problem reading a RFID reader

elunicotomas

Hi there,

I have this SparkFun RFID Starter Kit (https://www.sparkfun.com/products/13198?_ga=1.242738306.1686357739.1444361942), I followed the steps in the HookUp guide (https://learn.sparkfun.com/tutorials/sparkfun-rfid-starter-kit-hookup-guide?_ga=1.177165093.1278763627.1444260091), and It seems that is working fine, although I'm not getting the same reads as the guide.

Example: The guide shows this screenshot of the Arduino serial port while reading the card:

And I get this value:

If I swipe the card another time, I get this reading:

What are those little squares? I guess is some kind of character but I don't know which, or why is there.

Any ideas?

I am also trying this RFID reader in Processing. To change a message in the screen if someone swipes the card.

Initial screen:

After one read:

The text "saldo en 0" should have changed to "deposito $50"", but it shouldn't.

Any ideas?

Thanks!!

The code:

import processing.serial.*;
Serial myPort;
String inString = "texto inicial";
String mensaje;

void setup () {
  size(400, 300);        
  println(Serial.list());
  myPort = new Serial(this, Serial.list()[0], 9600);
  myPort.bufferUntil('\n');
  background(0);
}
void draw () {
  background(0);
  String s = inString;
  String comparador = "4500B8C02A17";
  textSize(24);
  fill(100);
  text(s, height/3, width/3); 

  if (comparador.equals(s) == true) {
    mensaje = "deposito $50";
  } else {
    mensaje = "saldo en 0";
  }
  text(mensaje, height/3, width/3+30);
}

void serialEvent (Serial myPort) {
  inString = myPort.readStringUntil('\n');
}

GoToLoop

// forum.processing.org/two/discussion/12920/problem-reading-a-rfid-reader
// 2015-Oct-09

import processing.serial.Serial;

static final String COMPARADOR = "4500B8C02A17";
static final String DEPOSITO = "Deposito $50";
static final String SALDO = "Saldo en 0";

String mensaje = "Texto inicial";

void setup() {
  size(400, 300);
  noLoop();

  textAlign(LEFT, BOTTOM);
  textSize(24);
  fill(0200);

  String[] portas = Serial.list();
  printArray(portas);

  new Serial(this, portas[0], 9600).bufferUntil(ENTER);
}

void draw() {
  background(0);

  text(mensaje, width/3, height>>1);
  text(COMPARADOR.equals(mensaje)? DEPOSITO : SALDO
    , width/3, height/2 + 30);

  frame.setTitle("Frame: #" + frameCount);
}

void serialEvent(Serial s) {
  mensaje = s.readString().trim();
  redraw = true;
}

elunicotomas

@GoToLoop it works! =D> now I need an explanation! :-?

GoToLoop

You'd have to be more specific where you don't get it... >-)

elunicotomas

@GoToLoop please see my comments in the code, thanks!

// forum.processing.org/two/discussion/12920/problem-reading-a-rfid-reader // 2015-Oct-09

import processing.serial.Serial;

static final String COMPARADOR = "4500B8C02A17"; // why static final String ?? I don't know what it is
static final String DEPOSITO = "Deposito $50";
static final String SALDO = "Saldo en 0";

String mensaje = "Texto inicial";

void setup() {
  size(400, 300);
  noLoop();

  textAlign(LEFT, BOTTOM);
  textSize(24);
  fill(0200);

  String[] portas = Serial.list();
  printArray(portas);

  new Serial(this, portas[0], 9600).bufferUntil(ENTER); // is the same as myPort.bufferUntil('\n'); ????
}

void draw () {
  background(0);
  text(mensaje, width/3, height>>1);
  text(COMPARADOR.equals(mensaje)? DEPOSITO : SALDO
    , width/3, height/2 + 30);
  frame.setTitle("Frame: #" + frameCount); // what is this line for??
}

void serialEvent(Serial s) {
  mensaje = s.readString().trim(); // why do you trim? 
  redraw = true; // what does redraw ???
}

GoToLoop

Why static final String ?? I don't know what it is.

https://processing.org/reference/final.html
https://processing.org/reference/static.html

Is the same as myPort.bufferUntil('\n'); ????

Yes, ENTER = '\n' = 10 = 0xA. ;)
Though I'm not using a variable, I'm calling bufferUntil() over the newly created Serial.

frame.setTitle("Frame: #" + frameCount);

setTitle() changes window bar's title.
frameCount: https://Processing.org/reference/frameCount.html

Why do you trim()?

B/c Serial is programmed to bufferUntil(ENTER);. So we need to trim() that ending \n: :-B
https://Processing.org/reference/trim_.html

What does redraw???

It's what redraw() does internally: https://processing.org/reference/redraw_.html

Since noLoop() was issued in setup(), the auto-draw() has been turned off.
So every time serialEvent() is called back by the Serial's instance, we need to redraw() once.

elunicotomas

@GoToLoop You are the man! ^:)^

Two more questions: 1) Why to set the title with the frame count? 2) I didn't know about the noLoop(). Why did you use it? I mean Why no leave the program running the draw automatically like usuall?

(sorry for my non-native english)

GoToLoop

1. Why to set the title with the frameCount?
   It's just informative. So we know how many times serialEvent() has happened. :P
2. Why no leave the program running the draw() automatically like usual?
   By default Processing calls back draw() at about 60 FPS.
   We can change that via frameRate() though: https://Processing.org/reference/frameRate_.html
   We could just let it roll of course. But why waste CPU/GPU/APU to display the same thing?
   Variable mensaje only changes inside SerialEvent() after all.
   Until then text() is gonna display the same thing over & over @ 60 FPS.
   It only makes sense to update the canvas once it actually has something new to display!
   Besides, I wanted frameCount to represent how many times serialEvent() had happened.
   W/o noLoop(), frameCount would increase at about 60 each second!
3. Sorry for my non-native English.
   I'm Brazilian and speak Portuguese! :-h

elunicotomas

Again, obrigado! =D> very helpful and explicative. Cheers from Argentina. :-h

elunicotomas

Uma última pergunta: I want that when mensaje is the same as COMPARADOR, the text Deposito $50 is displayed only for 5 seconds and then go back to Saldo en 0 is this OK?

import processing.serial.Serial;

static final String COMPARADOR = "4500B8C02A17";
static final String DEPOSITO = "Deposito $50";
static final String SALDO = "Saldo en 0";

String mensaje = "Texto inicial";

int tiempo;
int espera = 5000;

void setup() {
  size(400, 300);

  textSize(24);
  fill(0200);

  String[] portas = Serial.list();
  printArray(portas);

  new Serial(this, portas[0], 9600).bufferUntil(ENTER);

  tiempo = millis();
}

void draw () {
  background(0);
  text(mensaje, height/3, width/3);
  text(COMPARADOR.equals(mensaje)? DEPOSITO : SALDO
    , height/3, width/3 + 30);

  if (COMPARADOR.equals(mensaje)) {
    if (millis() - tiempo >= espera) {
      mensaje = SALDO;
      tiempo = millis();
    }
  }
  println(mensaje);
}

void serialEvent(Serial s) {
  mensaje = s.readString().trim();
}

GoToLoop

• Seems so. But then you had to remove noLoop() and thus draw() is called back @ 60 FPS.
• As an alternative proposal, rather than having draw() looping all the time, just turn it on as long as the display timer is going on.
• After that, issue noLoop() and await serialEvent() to loop() it again.
• And since serialEvent() & draw() are run by diff. Threads, I'm relying on synchronized () in order to "atomize" the entire steps.
• Still you need to consider the possibility that a new "deposit" could happen in less than 5 seconds...

// forum.processing.org/two/discussion/12920/problem-reading-a-rfid-reader
// 2015-Oct-10

import processing.serial.Serial;

static final String COMPARADOR = "4500B8C02A17";
static final String DEPOSITO = "Deposito $50";
static final String SALDO = "Saldo en 0";

String mensaje = "Texto inicial";

static final int FPS = 1, ESPERA = 5 * FPS;
int stopFrame;

void setup() {
  size(400, 300);
  frameRate(FPS);

  textAlign(LEFT, BOTTOM);
  textSize(24);
  fill(0200);

  String[] portas = Serial.list();
  printArray(portas);

  new Serial(this, portas[0], 9600).bufferUntil(ENTER);
}

void draw() {
  synchronized (this) {
    if (frameCount == stopFrame) {
      noLoop();
      mensaje = str(frameCount);
    }
  }

  background(0);
  text(mensaje, width/3, height>>1);
  text(COMPARADOR.equals(mensaje)? DEPOSITO : SALDO
    , width/3, height/2 + 30);
}

synchronized void serialEvent(Serial s) {
  mensaje = s.readString().trim();
  stopFrame = frameCount + ESPERA;
  loop();
}

elunicotomas

@GoToLoop Again, thanks! very clear and explicative. Now I'll continue a bit by myself :P Have a nice weekend!

elunicotomas

I'm trying to change the code a bit but with no success L-)

Why this:

    if (COMPARADOR.equals(mensaje)) {
        mensaje = DEPOSITO;
      } else {
        mensaje = SALDO;
      }
      text(mensaje, height/3, width/3 + 30);

Is no the same as this:

text(COMPARADOR.equals(mensaje)? DEPOSITO : SALDO, height/3, width/3 + 30);

I mean... I guess is not the same because the program does different things using one or the other. And the thing is that now I need more things to happen (displaying an image among other simple things) if COMPARADOR equals mensaje, rather than displaying some text.

Any ideas?

elunicotomas

My mystake, I've updated the code:

        if (COMPARADOR.equals(mensaje)) {
            text(DEPOSITO, height/3, width/3 + 30);
          } else {
            text(SALDO, height/3, width/3 + 30);
          }