AI on the Edge LESSON 12: Introduction to Python Threading on the Raspberry Pi

The challenge we face as we move forward in this class is that certain important functions which we need are ‘Blocking’ in nature. That is, they block the remainder of the program as they wait for input. For example, imagine blinking an LED and having the user input the delay time. When the program is waiting for user input, it can not continue to perform the blinking operation. This is also true for speech input. While the program waits for you to say something, execution of the remainder of the program stalls. To overcome this, we use threads. Threads are functions, or small snippets of code, which we can have execute in the background. In today’s lesson, I will show you how to incorporate threading into your AI projects.

In today’s lesson, this is the code we developed.

from fusion_hat.pin import Pin, Mode
import threading
from queue import Queue
from time import sleep

redPin = 17
redLED = Pin(redPin, Mode.OUT)
redLED.low()

blinkDelay = 1.0
running = True
blinkQ = Queue()
def blinkTime():
    print("Input Thread is Running")
    global running
    while running:
        cmd = input("Input Blink Time in Seconds, or Q for Quit: ")
        if cmd.upper()== "Q":
            running = False
            break
        blinkQ.put(float(cmd))
    print("Thread is Terminated")
blinkThread = threading.Thread(target=blinkTime,daemon=True)
blinkThread.start()
print("Main Program Has Commenced!")
try:
    while running:
        if blinkQ.empty()==False:
            blinkDelay = blinkQ.get()
        redLED.high()
        sleep(blinkDelay)
        redLED.low()
        sleep(blinkDelay)
    redLED.low()
    print("Program Terminated")
        
except KeyboardInterrupt:
    running = False
    redLED.low()
    print("LED Released")
    print("Program Terminated")

from fusion_hat.pin import Pin, Mode

import threading

from queue import Queue

from time import sleep

redPin = 17

redLED = Pin(redPin, Mode.OUT)

redLED.low()

blinkDelay = 1.0

running = True

blinkQ = Queue()

def blinkTime():

print("Input Thread is Running")

global running

while running:

cmd = input("Input Blink Time in Seconds, or Q for Quit: ")

if cmd.upper()== "Q":

running = False

break

blinkQ.put(float(cmd))

print("Thread is Terminated")

blinkThread = threading.Thread(target=blinkTime,daemon=True)

blinkThread.start()

print("Main Program Has Commenced!")

try:

while running:

if blinkQ.empty()==False:

blinkDelay = blinkQ.get()

redLED.high()

sleep(blinkDelay)

redLED.low()

sleep(blinkDelay)

redLED.low()

print("Program Terminated")

except KeyboardInterrupt:

running = False

redLED.low()

print("LED Released")

print("Program Terminated")

Making The World a Better Place One High Tech Project at a Time. Enjoy!