Changing blinking duration of LED by using 2 pushbuttons and arduino - arduino

Question

I'm trying to make an arduino UNO circuit that allows me to set the blinking duration of an LED with two pushbuttons, but I'm having trouble with the program. First of all, the default blinking duration is 0,5 s. And I want to program the first pushbutton to be able to extend the blinking duration by 0,1 seconds, whereas the second one is for speeding up the duration by 0,1 seconds.
So in my current code, I use if statements to check whether the two buttons are pressed or not. If the inc button is pressed, the program should increase the duration by 100 ms, whereas when dec button is pressed, the program should decrease the duration by 100 ms.
However when I run it on the arduino circuit, the duration is stuck in 600 and 500. So in every loop, the program adds 100 ms to the duration time and then decreases it again by 100, even when I do nothing to the buttons.
Here's my code so far:
const int led = 7;
const int buttonUp = 6;
const int buttonDown = 5;
int duration = 500;
void setup(){
pinMode(led, OUTPUT);
pinMode(buttonUp, INPUT);
pinMode(buttonDown, INPUT);
Serial.begin(9600);
}
void loop(){
int inc = digitalRead(buttonUp);
int dec = digitalRead(buttonDown);
if(inc == HIGH){
duration += 100;
Serial.println(duration);
}
if(dec == HIGH){
duration -= 100;
if(duration < 0){
duration = 100;
}
Serial.println(duration);
}
digitalWrite(led, HIGH);
delay(duration);
digitalWrite(led, LOW);
delay(duration);
}
the code and circuit
serial monitor
Will be extremely grateful if anyone can point out any mistakes!! Thank you!

Answer 1

duration is 500ms. So you basically poll your button states once every second. The time window where you can detect a button click is very short compared to the time you cannot detect it. So chances that you register a click are very little. You need to push the button for at least a second to capture the signal every time.
If you push both buttons you add and subtract 100. That's a total change of 0. What do you expect?
This can be avoided by checking your button state more frequently or by using interrupts.
Find out how to use non-blocking delays and interrupts. The internet is full of tutorials.

Answer 2

bool blink(unsigned int duration) {
// demo code only
// (usable only once per sketch, due to static variables)
static unsigned long last;
static bool state;
if (millis() - last >= duration) {
last = millis();
state = ! state;
}
return state;
}
This is the BlinkWithoutDelay pattern. Usage:
digitalWrite(led,blink(duration));
Button handling is trickier than a beginner thinks: often you want to detect a state change between pressed and released, and you want to ignore the bouncing of a mechanical switch happening during a state change. Or you want to repeat some action, when the button is pressed for a long time.
Easiest you do a little delay(10); after detecting a state change to pass the bouncing time. Or look for libraries doing all that button handling.
Or do such a lazy delay anyway, to slow down your fast microcontroller below button bouncing speed.
const int led = 7;
const int buttonUp = 6;
const int buttonDown = 5;
void setup(){
pinMode(led, OUTPUT);
pinMode(buttonUp, INPUT);
pinMode(buttonDown, INPUT);
Serial.begin(9600);
}
unsigned int duration = 500;
int lastbutton = 0; // 0 / -100 / +100 to detect button changes
void loop(){
bool inc = digitalRead(buttonUp);
bool dec = digitalRead(buttonDown);
delay(5); // debounce
if( (inc || dec) && lastbutton == 0){
lastbutton = (inc - dec) * 100;
duration += lastbutton;
if (duration == 0) duration = 100; // Minimum
Serial.println(duration);
}
if (lastbutton != 0 && !inc && !dec) lastbutton = 0;
digitalWrite(led, blink(duration) );
}