ButtonPressLEDs_example

# ButtonPressLEDs example programme
# This program waits for a button press (value becomes zero) ising an interrupt. When the button
# is pressed, the external (red/green multi color) LED will togglev to the other color.
# Note that as the button is directly connected to the board, it will have mechanical bouncing,
# hence in the code it will include debouncing code to overcome that. 
#  
# We first import the Pin class and initialize a global variable called interrupt_flag to 0.
# We will use this variable to keep track of the occurrence of interrupts.
# Global variables in MicroPython can be accessed by all functions.
# Then we create a pin object of the Pin class. GPIO 22 is set as an input with PULL_UP enabled.
from machine import Pin
import time

DEBOUNCE = 300    # 300 ms is what usually is used for button debouncing.
GPIO_BUTTON1 = 22 # Button1 is connected to GP22 port
GPIO_LEDRED = 1   # The Red led is connected to GP1 port
GPIO_LEDGREEN = 2 # The Green led is connected to GP2 port

interrupt_flag=0
debounce_time=0
Button1 = Pin(GPIO_BUTTON1,Pin.IN,Pin.PULL_UP)
ledred = Pin(GPIO_LEDRED, Pin.OUT)     #configure GPIO-1 Pin as an output pin and create and led object for Pin class
ledgreen = Pin(GPIO_LEDGREEN, Pin.OUT) #configure GPIO-2 Pin as an output pin and create and led object for Pin class

# Next, we define a function called callback() to handle interrupts. The code inside
# this function should not perform any complex task, as it needs to hand over CPU usage
# to the main program quickly. We set the interrupt_flag variable as 1. Note that we need
# to use the global keyword when we change a global variable inside a function.
def Button1_IsPressed(Button1):
    global interrupt_flag, debounce_time, DEBOUNCE
    if (time.ticks_ms()-debounce_time) > DEBOUNCE:
        interrupt_flag= 1
        debounce_time=time.ticks_ms()
    
# To attach the interrupt to the pin, we use irq() function. This function takes two arguments :
# trigger : trigger can be of the following types-
# (1) Pin.IRQ_FALLING– interrupt on falling edge.
# (2) Pin.IRQ_RISING– interrupt on rising edge.
# (3) Pin.IRQ_LOW_LEVEL – interrupt on LOW level.(Not supported in MicroPython for Pico at the time of publishing this article.)
# (4) Pin.IRQ_HIGH_LEVEL - interrupt on HIGH level.(Not supported in MicroPython for Pico at the time of publishing this article.)
# (5) Pin.IRQ_FALLING | Pin.IRQ_RISING – interrupt on both the rising edge and the falling edge.
#
# handler : handler specifies the function which will be called when an interrupt occurs.
#
Button1.irq(trigger=Pin.IRQ_FALLING, handler=Button1_IsPressed)

#
# In the while loop, we continuously check the value of the interrupt_flag variable.
# If this value is detected as ‘1’, that means an interrupt has occurred.
# We reset the variable to ‘0’ so that the variable can be set again when an interrupt occurs.
#
ledred.value(True)
ledgreen.value(False)
while True:
    if interrupt_flag is 1:
        interrupt_flag=0
        print("Interrupt Detected, the value of the button is: ", Button1.value())
        ledred.toggle()
        ledgreen.toggle()