How can the frequency of a square wave be determined using GPIO edge detection?

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To determine the frequency of a square wave using GPIO edge detection, follow these steps:

1. Attach the square wave signal to a GPIO input pin on the Raspberry Pi.
2. Enable edge detection on the GPIO pin using the GPIO library in Python.
3. Write a callback function that will be triggered whenever the GPIO pin detects a rising edge or a falling edge.
4. Within the callback function, increment a counter variable that keeps track of the number of edges that have been detected.
5. Set a timer for a specific duration, such as 1 second.
6. After the timer has expired, calculate the frequency of the square wave by dividing the number of edges counted by the duration of the timer.
7. Print or output the result of the frequency calculation.

Here is some sample code in Python:

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.IN)

counter = 0

def callback(channel):
    global counter
    counter += 1

GPIO.add_event_detect(18, GPIO.BOTH, callback)

time.sleep(1)

GPIO.remove_event_detect(18)

frequency = counter / 1

print(frequency)

This code sets up GPIO pin 18 as an input and enables edge detection on both rising and falling edges. Whenever an edge is detected, the callback function increments the counter variable. After 1 second, the number of edges is divided by the duration of the timer (1 second) to calculate the frequency, which is then printed to the console.