[TriEmbed] [OBSOLETE trianglearduino:1095] Problem with AtTiny85 and buttons

[Glen Smith]

I should have refreshed my inbox prior to writing my note. Sooner or later
I will learn this lesson.

Truth be told, for this application debouncing the switch is probably not
necessary, UNLESS you plan on eventually limiting the number of shots a
player gets in a game or before reloading. Which would prevent somebody
from holding the trigger & simply panning around during the play area.
On Jul 15, 2014 10:32 AM, "Adam Haile" <email at adamhaile.net> wrote:

> Joe,
>
> Easiest way to do the mentioned bias resistors is to use the one's built
> into the AT chip :)
> Every IO pin on the AT series chips have an internal pull-up resistor
> ranging from 10k-50k ohm (depending on the chip model).
>
> To enable it, you set the pin mode to input and then write a high bit to
> it. Sounds weird, but that's just the way the resisters work:
>
> pinMode(buttonPin, INPUT);
> digitalWrite(buttonPin, HIGH); //sets internal pull-up
>
> Then, simply wire your button to "pull" that pin to ground. i.e. hook one
> side of the button to buttonPin and the other to ground. When the button
> closes the bias is now ground because it has the least resistance and your
> micro will see LOW. See the following for more:
> http://arduino.cc/en/Tutorial/DigitalPins
>
> For debouncing, if you aren't too worried about not doing it the most
> efficient way try this: http://playground.arduino.cc/code/bounce
>
> At its simplest, you can do something like this:
>
> uint8_t _oldState = HIGH;
> uint8_t _curState = _oldState;
> long bounceThreshold = 100;//wait 100ms, increase or decrease depending on
> how sesitive you want the debouncing
>
> _curState = digitalRead(buttonPin);
> if(_curState != _oldState)
> {
> delay(bounceThreshold);
> if(_curState == digitalRead(buttonPin))
>  {
> if(_curState)
> {
> // turn LED on:
>  }
> else
> {
> // turn LED off:
>  }
> _oldState = _curState;
> }
> }
>
> It's pretty basic, but it gets the job done in most cases. Note, this
> should make it so the LED is on only while the button is actually down.
> It's not a toggle (press on/press off). To to that, in the if(_curSate)
> section just flip a boolean (ledState != ledState) and then at the end of
> that whole if statement do digitalWrite(ledPin, ledState);
>
> There's many ways to skin this one... personally I use external interrupts
> with buttons... but that's a whole other lesson. Though, side note. The
> reason the internal bias resistors are pull-up is that the chips are set to
> only be able to be woken from sleep when the external interrupt goes LOW.
> You can configure the interrupts to react to LOW or HIGH, but being woken
> from sleep is a special case and it looks like they simplified the chip
> circuit by requiring that a wake be a LOW pulse.
>
>
>
>
>
> On Tue, Jul 15, 2014 at 10:15 AM, Glen Smith <mrglenasmith at gmail.com>
> wrote:
>
>> I'm guessing that you have 2 problems. One is due to your input switch
>> bouncing. When a mechanical switch closes it does not simply change from
>> false to true. For a few milliseconds (immediately for us slow humans but
>> forever for a u-processor running this little bit of code) it bounces back
>> & forth between the two states. Regardless of how fast or hard you push
>> that switch, the Tiny85 will see many of these changes.
>>
>> The other thing you are running into is called a floating input. When you
>> set the button as an input, you need to use a resistor to bias the input to
>> return to a known level. Think of it like a lever, unless a spring pushes
>> or pulls the lever to a known state, when you let go of it, the lever will
>> simply stay where you left it. In the case of your input, you left it high,
>> so the charge on the input slowly dissipates, and a second or so later the
>> Tiny85 sees it as a low. These biasing resistors are called pull-up &
>> pull-down resistors.
>> On Jul 15, 2014 6:58 AM, "Bothari" <bothari at gmail.com> wrote:
>>
>>> Group,
>>>
>>> I've been learning about hardware for the last couple of months, but
>>> I've come up against a problem with inputs.  I put together a little IR gun
>>> with the AtTiny85, but I can't get the trigger to fire the gun.  I've
>>> reduced the problem to one AtTiny85 with a resistor and LED, but I still
>>> don't understand what's going on.
>>>
>>> With the below code (Blink from the examples) I can touch the #2 pin
>>> high and the light on pin 3 comes on, but it stays on for like a second or
>>> so before going off.  I think it should go off immediately.
>>>
>>> I added 3 blinks on the LED on startup to make sure I know when it
>>> resets, and the fuse bits for the oscillator are set to 8mHz.  That works
>>> as expected.
>>>
>>> Any ideas?
>>> Joe
>>>
>>> const int buttonPin = 2;     // the number of the pushbutton pin
>>> const int ledPin =  3;      // the number of the LED pin
>>>
>>> // variables will change:
>>> int buttonState = 0;         // variable for reading the pushbutton
>>> status
>>>
>>> void setup() {
>>>   // initialize the LED pin as an output:
>>>   pinMode(ledPin, OUTPUT);
>>>    digitalWrite(ledPin, LOW);
>>>   // initialize the pushbutton pin as an input:
>>>   pinMode(buttonPin, INPUT);
>>>
>>>   //Show that we rebooted
>>>   digitalWrite(ledPin, HIGH);
>>>   delay(300);
>>>   digitalWrite(ledPin, LOW);
>>>   delay(300);
>>>
>>>   digitalWrite(ledPin, HIGH);
>>>   delay(300);
>>>   digitalWrite(ledPin, LOW);
>>>   delay(300);
>>>
>>>   digitalWrite(ledPin, HIGH);
>>>   delay(300);
>>>   digitalWrite(ledPin, LOW);
>>>   delay(300);
>>> }
>>>
>>> void loop(){
>>>   // read the state of the pushbutton value:
>>>   buttonState = digitalRead(buttonPin);
>>>
>>>   // check if the pushbutton is pressed.
>>>   // if it is, the buttonState is HIGH:
>>>   if (buttonState == HIGH) {
>>>     // turn LED on:
>>>     digitalWrite(ledPin, HIGH);
>>>   }
>>>   else {
>>>     // turn LED off:
>>>     digitalWrite(ledPin, LOW);
>>>   }
>>> }
>>>
>>> --
>>> "There are only two industries that refer to their customers as
>>> ‘users’." - Edward Tufte
>>>
>>>  --
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>>
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