Hot answers tagged

18

Hold the RESET button as you plug the Arduino in and keep it pressed all the time it's plugged into your computer. Load Blink.ino into the IDE and compile it. Press the UPLOAD button in the IDE and move the mouse to somewhere "safe". Release the RESET button. Do those last three steps in rapid succession and you should be fine.


17

When a button is connected in that configuration, the input is what's called floating, meaning it's not a 0 or a 1. When the button is pressed, it is connected to ground, so that's definitely a 0, but when it's not pressed down, we don't know the value of the pin. Pull Up Resistor We need to include what's called a "pull-up" resistor to pull the signal up ...


14

The short answer is that you have 100 miliseconds to respond to the user if you want them to feel the action occurred instantaneously. According to Jacob Nielsen in his book Usability Engineering, from 1993, which is considered an important reference in Systems Usability and User Experience: 0.1 second is about the limit for having the user feel that ...


10

Contact Bounce This is known as contact bounce and happens when the metal contacts in the button or switch bounce against each other when you push it. The microcontroller is fast enough to pick up these bounces and, as far as it's concerned, you're toggling the switch many times in as much as 10 milliseconds of time. Different switches and buttons will ...


9

That resistor is called a pull-down resistor. It's there to make sure pin 2 read low when the button isn't pressed. If you don't put it there pin 2 is left 'floating', and it could erroneously read a high value. Google it for more info. If you want to simplify you circuit you could instead use a pull-up resistor, and connect the button to ground instead of ...


7

Just use the return value of digitalRead (which is 1 or 0) as the input to digitalWrite: int btnVal = digitalRead(3); digitalWrite(4, btnVal); // On when button is HIGH digitalWrite(5, 1 - btnVal); // Off when button is HIGH Or using boolean instead: bool btnVal = digitalRead(3); digitalWrite(4, btnVal); // On when button is HIGH digitalWrite(5,...


6

The answer depends on exactly how the sketch is meant to respond to the user interaction. External interrupts If the interaction depends on responding very accurately to the rising or falling edge of an input event (as in your example), then an external interrupt may be the way to go, if possible. This is particularly important if the input event might be ...


6

At the moment, you've got two main problems. Firstly, both your if statements are being triggered one after the other. This is because the first if statement sets x to 0, which is part of the condition the second if statement looks for. The second problem is that you're not monitoring the previous state of the button. buttonState will appear HIGH every time ...


6

Use the analog comparator in the ATmega328P to trigger an interrupt once the input voltage rises enough to indicate a button press. Connect the analog network to both the analog input and D6. If your lowest analog voltage is not greater than 1.2V then apply a voltage greater than 0V but more than 40mV less than your lowest analog voltage to D7. If you have ...


6

The analog pins function as digital pins number 14 - 19, with 14 being A0 and 19 being A5. I had hooked it up backwards. This time we're gonna get funky Everybody check your pins Check check check check your pins Check check check check your pins


6

The Button library in the Arduino playground works perfectly.


6

I've used NRF24L01+ chipset 2.4GHz wireless modules with Arduino before, and found them to be great, and super cheap (~$10 for 10 of them on ebay!). They have 3 modes of transmission: 250kbps, 1Mbps, and 2Mbps. The range decreases accordingly with higher bitrate, but the time spent sending a message does too. There are multiple Arduino libraries (e.g. RF24, ...


6

There must be a difference between a LOW reading and no connection, correct? No, the input circuitry measures a voltage. The exact details are in the datasheet, but how could it know there is nothing connected? There is not some sort of sensor that detects the insertion of a wire into the input. Therefore it is trying to read a voltage all the time. With ...


5

If you are using the pin as an input in close proximity to the Arduino there is little reason to use an external pullup. There are a number of factors to consider. If the switch is some distance from the chip and/or in a noisy environment it will be more susceptible to interference as the internal pullups are high impedance (20kΩ to 150kΩ depending on ...


5

Put the strings to display in an array, and output them instead. char const * const stateDisplay[] = {"Off", "On"}; ... lcd.print(stateDisplay[state]);


5

If you just want the reset button to change the program mode, the simplest thing would be to let the button reset the Arduino and switch modes each time your program restarts. Then you do not need to change the fuses or get a high voltage programmer. The code would look like this: void setup() { // At startup, switch to the next mode. if (++mode >...


4

The behavior you describe is symptomatic of a floating input. I guess you have directly wired your buttons between input pins and +5V (or GND, that won't change the observed behavior). The problem is when you don't push the button, the input pin is left floating and can be read as HIGH or LOW based on strange factors. The solution to this is to use pullup ...


4

This behavior is expected: INPUT_PULLUP means the pin is pulled up via the internal pull up, i.e. it will read as high if not connected externally. With your push button you connect it to ground (0 volts), thus bringing it to low level and it will read as low. Therefore, in your code, you need to check for low level (LOW) to check if the button is pressed (...


4

pinMode(one, INPUT); You have configured the input with no pullup. Since it is a CMOS input and hence very high impedance, it effectively acts as an antenna picking up random signals including that of your finger becoming capacitively coupled to it. You must enable the pullup on the pins (and connect the common to ground) if you want correct operation. ...


4

You can use the internal pullup e.g. pinMode(inPin, INPUT_PULLUP); Then wire your switch between pin and Gnd.


4

This probably won't answer your question completely, but here are some notes from me: buttonState = current ; //read value again now that bouncing is over This won't read the value again, it just copies current into buttonValue. What you wanted is: buttonState = digitalRead(BUTTON); // read value again now that bouncing is over You have multiple issues ...


4

The pins on each side of the button are shorted, the "button" is between the sides of the button. Else your code looks alright. Edit: Here's an image which shows how a push button is connected internally, make sure you're using the correct pins.


4

They Keyboard.press() command accept modifiers per the documentation . You may need to do multiple press() commands before releasing. For example, if you want to launch Explorer you could use: Keyboard.press(KEY_LEFT_GUI); Keyboard.press('e'); Keyboard.releaseAll(); This is equivalent to shortcut keys windows + e The modifier GUI is what stands in for ...


4

You can likely user an I/O pin as an output to "power" fairly high-impedance devices such as pullup resistors for buttons, or even potentiometers of moderate to high total resistance. A reason you might wish to do so would to be able to stop the device from draining power while the entire system is in a low-power sleep mode, or to otherwise disable it ...


4

I concur with Majenko, although your code would work, the code is blocking, meaning that your code stops at that point until the button is released again. The remaining code in your loop does not execute until the button is resolved. A much better method is to check the state of the button in each passing of the loop. If the state changes (ie goes low) you ...


4

"I usually put a capacitor next to my push button" A 1uF capacitor across the button is easy, cheap and means no need to fiddle with debouncing codes. See Nick Gammon's excellent switch tutorial that covers almost any conceivable situation when using switches with Arduinos and clones (high or low, GND or +5V, internal pull-up or pull-down, capacitor ...


4

I think, that the problem is in ideb_read, which expects "a pointer to (non-volatile) structure" and so it does not care about re-reading ideb->output if it can it optimize out somehow (say putting it in free register). IMHO the ideb_read should have parameter declared as (volatile IntegratingDebounce *ideb) (to know, that structure pointed by ideb is ...


4

Getting pointer declarations right can be anything but obvious, especially where const and volatile are concerned (which are syntactically equivalent). Your problem stemmed from the confusion between "volatile pointer to struct" and "pointer to volatile struct". See the difference? In words it's fairly clear. In C, it has you - and me - running to your C ...


4

The circuit you have made is only using Arduino as a 5V power source. You aren't using any GPIO pins to read the state of the button or to control the LED by an output pin. You've just made a plain-old circuit with a button and LED in series with a power source. Often for a button-controlling-LED sketch, you will have a button connected between GND and an I/...


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