Teensy » A curious mind

Switch bounce counter

Sep 022012

I was curious to see if the new switches were prone to switch bounces. This is why I wrote a quite simple Teensy program that can count switch bounces. The debounce example code that come with the Arduinio IDE was used as a template.

This is quite simple, and just here to make it simple to redo this kind of test when I get new types of switches.

S1 in the schematic is the switch you want to test. The resistor is used as a pull down resistor, to make sure that the input pin is properly grounded when the button is released.

The result for my switches is somewhat unstable. I get just one count most of the times, but sometimes up to 9 bounces. The end result is that I need to debounce them properly to eliminate weird results in my builds.

Schematic

// Count bounces
// Open the serial monitor in the Arudino IDE, it will be used for count feedback

const int buttonPin = 2; // Teensy pin to connect the switch to
const int ledPin = 11;   // Built in LED for visual feedback
int buttonState;
int lastButtonState = LOW;
long lastDebounceTime = 0;
long debounceDelay = 100; // Bounce period set to 0.1s
int bounces = 0;
int lastLedState = LOW;

void setup() {
  pinMode(buttonPin, INPUT);
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);    // Open the serial port to write the bounce counts to
}

void loop() {
  int reading = digitalRead(buttonPin);

  if (reading != lastButtonState) {
    lastDebounceTime = millis();
    bounces++; // Count bounces
  }

  if ((millis() - lastDebounceTime) &gt; debounceDelay) {
    if (reading != lastLedState) {
      Serial.println(bounces); // Write # bounces to serial console
      bounces = 0;             // Zero the counter
      lastLedState = reading;
    }
  }

  digitalWrite(ledPin, lastLedState);
  lastButtonState = reading;
}

// Count bounces

// Open the serial monitor in the Arudino IDE, it will be used for count feedback

const int buttonPin = 2; // Teensy pin to connect the switch to

const int ledPin = 11; // Built in LED for visual feedback

int buttonState;

int lastButtonState = LOW;

long lastDebounceTime = 0;

long debounceDelay = 100; // Bounce period set to 0.1s

int bounces = 0;

int lastLedState = LOW;

void setup() {

pinMode(buttonPin, INPUT);

pinMode(ledPin, OUTPUT);

Serial.begin(9600); // Open the serial port to write the bounce counts to

}

void loop() {

int reading = digitalRead(buttonPin);

if (reading != lastButtonState) {

lastDebounceTime = millis();

bounces++; // Count bounces

}

if ((millis() - lastDebounceTime) > debounceDelay) {

if (reading != lastLedState) {

Serial.println(bounces); // Write # bounces to serial console

bounces = 0; // Zero the counter

lastLedState = reading;

}

digitalWrite(ledPin, lastLedState);

lastButtonState = reading;

}

The Teensys have arrived

Electronics, Teensy No Responses »

Aug 282012

The new Teensys arrived from PJRC yesterday. That was a really nice surprise since the expected delivery time said to be one to three weeks. So I got my delivery well in the lower region of that span, a really nice surprise.

And guess what, it was my lucky day yesterday. I got another shipment as well yesterday, from Sparkfun Electronics. Mostly breakout boards for various cards like SD, microSD, SIM and smart cards. Nice to have at home when I start to get curious about fuzzing around with those. also got some new lab cables that I am quite short of. I also got a transparent RFID tag, for demos and presentations and a little IRDA-receiver that will be used in my XBMC setup.

I hope the Chinese stuff start to arrive soon as well. There are some displays and other fun things that I am waiting for, before the real fun can start.

New Teensys on the way

Electronics, Teensy No Responses »

Aug 182012

My old Teensy 2.0 always seem to end up in more than one project. Constantly having to be reprogrammed for different stuff I wanna try. The most common are to use it for injecting malicious code with SET or to have it act as a USB disk with various bad formatted vendor tag etc. Now I have another thing I want to use it for that involves a lot of prototyping so I can’t carry it with me as I usually always do.

The simple solution was of course to order some more So now I have two more Teensy 2.0, one Teens++ 2.0 and one of each with pre-mounted protoboard pins. I hope I won’t run out of Teensys now for a while.

I did of course make sure to by some fun breakout boards for sim-, sd-, micro sd-, and smartcards as well. The fun will begin in a few weeks, stay tuned for more fun coming projects.