/*
State change detection (edge detection)
2024-05-05: modified to do a Bresenham PLL ratio of pulses between the input and output
for https://forum.arduino.cc/t/working-with-pwm/1256186/13
https://wokwi.com/projects/397099785583173633
Often, you don't need to know the state of a digital input all the time, but
you just need to know when the input changes from one state to another.
For example, you want to know when a button goes from OFF to ON. This is called
state change detection, or edge detection.
This example shows how to detect when a button or button changes from off to on
and on to off.
The circuit:
- pushbutton attached to pin 2 from +5V
- 10 kilohm resistor attached to pin 2 from ground
- LED attached from pin 13 to ground through 220 ohm resistor (or use the
built-in LED on most Arduino boards)
created 27 Sep 2005
modified 30 Aug 2011
by Tom Igoe
This example code is in the public domain.
https://docs.arduino.cc/built-in-examples/digital/StateChangeDetection/
*/
// this constant won't change:
const int buttonPin = 2; // the pin that the pushbutton is attached to
const int ledPin = 13; // the pin that the LED is attached to
// Variables will change:
int buttonPushCounter = 0; // counter for the number of button presses
int buttonState = 0; // current state of the button
int lastButtonState = 0; // previous state of the button
int outState = LOW; // current state of the output pulser
int lastOutState = LOW;
int outPulseCounter = 0;
// pulse ratio constants / Bresenham Algorithm variables:
// https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm
const unsigned int inputPPR = 600;
unsigned int outputPPR = inputPPR * 53UL /100;
int bresenhamSum = inputPPR/2;
void setup() {
// initialize the button pin as a input:
pinMode(buttonPin, INPUT_PULLUP);
// initialize the LED as an output:
pinMode(ledPin, OUTPUT);
// initialize serial communication:
Serial.begin(115200);
Serial.print("");
}
void loop() {
// read the pushbutton input pin:
buttonState = digitalRead(buttonPin);
// compare the buttonState to its previous state
if (buttonState != lastButtonState) {
// if the state has changed, increment the counter
if (buttonState == LOW) {
// if the current state is HIGH then the button went from off to on:
buttonPushCounter++;
Serial.println("on");
Serial.print("number of button pushes: ");
Serial.println(buttonPushCounter);
bresenhamSum += outputPPR;
if(bresenhamSum >=inputPPR)
{
bresenhamSum -= inputPPR;
outState = HIGH;
++outPulseCounter;
}
Serial.print("number of outputPulses:");
Serial.println(outPulseCounter);
Serial.print("Bresenham Decision Sum:");
Serial.println(bresenhamSum);
} else {
// if the current state is LOW then the button went from on to off:
Serial.println("off");
outState = LOW;
}
// Delay a little bit to avoid bouncing
delay(50);
}
// save the current state as the last state, for next time through the loop
lastButtonState = buttonState;
// toggles the output to match the outState when it changes:
if (outState != lastOutState) {
digitalWrite(ledPin, outState);
lastOutState = outState;
}
}