Arduino UNO code used in AGU Digital System Design Capsule Project to plot clock output and calculate frequency

plotter.ino

/*
You might need to change the plotter
history size to see everything cleaner.

Here is a good tutorial for this: 
https://youtu.be/qrfpPuw2W3A
*/

const int analogPin = A0; // Clock output pin
const int threshold = 512; // Midpoint (~2.5V for a 5V signal)
unsigned long lastTime = 0;
unsigned long period = 0;
bool lastState = LOW;

void setup() {
 	Serial.begin(9600);
}

void loop() {
	int signal = analogRead(analogPin);
	bool currentState = (signal > threshold); // Detect HIGH or LOW state

	// Detect a rising edge (LOW -> HIGH transition)
	if (currentState == HIGH && lastState == LOW) {
		unsigned long currentTime = millis();
		period = currentTime - lastTime;
		lastTime = currentTime;
	}
	lastState = currentState;

	// Calculate frequency (Hz)
	float frequency = (period > 0) ? (1000.0 / period) : 0;

	// Send data for plotting
	Serial.print("Signal:");
	Serial.print((signal / 1023.0) * 5.0, 3); // Signal for plotting
	Serial.print(",");
	Serial.print("Frequency:");
	Serial.println(frequency, 3); // Frequency measurement

	delayMicroseconds(2500); // Change this for smoother plot
}