ESP8266 Community Forum

- Sun Jun 12, 2016 11:18 am #49069 Hi all,

I have a button problem with plugged on ESP8266.

I followed the instructions of the arduino site
https://www.arduino.cc/en/Tutorial/Button

The resistor I use is 10k.

Problem is that when I press the button led is off and when button released led is on.

I measured Voltage on the digital pin when button is pressed and is 3.3v as expected.

What am I doing wrong???


Thx all

My Code is

Code: Select allconst int buttonPin = 5;     // the number of the pushbutton pin
const int ledPin =  16;      // the number of the LED pin

int buttonState = 0;         // variable for reading the pushbutton status

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT);
}

void loop() {
  buttonState = digitalRead(buttonPin);

  if (buttonState == HIGH) {
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(ledPin, LOW);
  }
}



Attachments

- Sun Jun 12, 2016 11:35 am #49070 That is the correct function based on your program and the way the led is usually connected to the uC's.
The leds anode is connected to vdd via resistor. The cathode is connected to the uC pin.
So when you make the pin go low, the current can flow from vdd through the resistor, the led an finally the gpio to gnd --> led lights up.
So leds on uC pins usually have inverted logic. To compensate, you can invert yout buttons logic too: swap button and resistor...

- Sun Jun 12, 2016 11:58 am #49071

That is the correct function based on your program and the way the led is usually connected to the uC's.
The leds anode is connected to vdd via resistor. The cathode is connected to the uC pin.
So when you make the pin go low, the current can flow from vdd through the resistor, the led an finally the gpio to gnd --> led lights up.
So leds on uC pins usually have inverted logic. To compensate, you can invert yout buttons logic too: swap button and resistor...

thx schufti

I am a newbee on electronics. Based on the arduino guide:
https://www.arduino.cc/en/Tutorial/Button

>>> ......This example turns on the built-in LED on pin 13 when you press the button.



It is the internal onboard led that has this behaviour.
If I connect an external led on a digital pin then I get what is expected.

thx again

- Sun Jun 12, 2016 12:10 pm #49072 It is simply that NodeMCU on-board LED is connected in Sink mode.