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Author: johnnohj

examples/asyncio_event_example.py

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+# SIMPLE ASYNCIO EVENT EXAMPLE
+
+# Brief program that illustrates using Events to coordinate tasks
+# within Asyncio programs. The present example involves only one led
+# and one event, but Asyncio allows a high degree of scaling. Adding
+# several copies of the functions 'blink', 'input_poll', or 'state'
+# should be straightforward with changes to names and objects.
+
+import board
+import time
+import adafruit_ticks
+import digitalio
+from adafruit_debouncer import Debouncer
+import neopixel
+import asyncio
+
+# Import library modules, as is tradition
+
+pin = digitalio.DigitalInOut(board.BUTTON)
+pin.direction = digitalio.Direction.INPUT
+pin.pull = digitalio.Pull.UP
+button = Debouncer(pin)
+
+# Instantiate the input, in this case, the 'BOOT' button on a
+# QT Py 2040. The debouncer ensures a clean hit.
+
+BLANK = (0, 0, 0, 0)
+RED = (255, 0, 0)
+GREEN = (0, 255, 0)
+BLUE = (0, 0, 255)
+
+COLORS = {0: BLANK, 1: RED, 2: GREEN, 3: BLUE}
+
+# Define the various colors according to preference and set them into
+# a dictionary for later retrieval. (Blue is not used in this code.)
+
+class color:
+    def __init__(self, initial_value):
+        self.value = initial_value
+
+# Create a class to hold and track the color while code executes.
+
+async def blink(color):
+    with neopixel.NeoPixel(board.NEOPIXEL, 1, brightness=0.1) as led:
+        while True:
+            led[0] = COLORS.get(0)
+            await asyncio.sleep(1)
+            led[0] = COLORS.get(color.value)
+            await asyncio.sleep(0)
+
+# Instantiate the led using 'with ... as' construction to keep this
+# function from blocking. 'COLORS.get(0)' indicates the led should show
+# no color (i.e., turn off), while 'COLORS.get(color.value)' instructs
+# the led to show the color pulled from the dictionary via the color
+# class' color.value. The line 'asyncio.sleep(1)' sets the blink rate;
+# in this case, once per second.
+
+async def input_poll(swapper):
+    count = 0
+    while True:
+        button.update()
+        if button.fell:
+            print('Press!')
+            if count == 0:
+                count += 1
+                print('Event is set!')
+                swapper.set()
+            elif count == 1:
+                count -= 1
+                print('Event is clear!')
+                swapper.clear()
+        await asyncio.sleep(0)
+
+# This function checks the button for activity and sets or clears the
+# Event depending on the button activity reflected in the 'count' variable.
+# The count begins set at 0 and is alternatingly incremented (count += 1)
+# and decremented (count -= 1) with each press of the button.
+
+async def state(swapper, color):
+    while True:
+        if swapper.is_set():
+            color.value = 2
+        else:
+            color.value = 1
+        await asyncio.sleep(0)
+
+async def main():
+
+    color.value = 1
+    COLORS.get(color)
+
+# Sets the color the led will first show on start
+
+    swapper = asyncio.Event()
+
+# Creates and names the Event that signals the led to change color
+
+    blinky = asyncio.create_task(blink(color))
+    poll = asyncio.create_task(input_poll(swapper))
+    monitor = asyncio.create_task(state(swapper, color))
+
+# Creates and names Tasks from the functions defined above
+
+    await asyncio.gather(monitor, blinky, poll)
+
+# Don't forget the 'await'! The 'asyncio.gather()' command passes the
+# listed tasks to the asynchronous scheduler, where processing resources
+# are directed from one task to another depending upon whether said task
+# has signalled its ability to 'give up' control by reaching the 'await
+# asyncio.sleep()' line.
+
+asyncio.run(main())