008 - ESP32 MicroPython: Hardware Timer Interrupts

Sep 26, 2020 · 3 min read · esp32 micropython esp32 timer interrupt Micropython esp32 micropython hardware timer interrupt micropython timer interrupt ·

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Introduction

In this tutorial, we will learn how to use the hardware Timer Interrupts of ESP32 in MicroPython. Timer in essence is basically a counter that either counts up or counts down. Timers can be use to trigger an interrupt event when an overflow happened or a certain count value is reached.

Circuit Diagram

Video Demonstration

Call To Action

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Source Code

Example # 1 Simple Timer:

 1import machine
 2
 3led = machine.Pin(2, machine.Pin.OUT)
 4
 5tim0 = machine.Timer(0)
 6
 7def handle_callback(timer):
 8    led.value( not led.value() )
 9
10# tim0.init(period=2000, mode=machine.Timer.ONE_SHOT, callback=lambda t: led.value(not led.value()))
11tim0.init(period=50, mode=machine.Timer.PERIODIC, callback=handle_callback)

Example # 2 Hardware Timer Interrupts use for multithreading:

 1# Load the machine module
 2import machine
 3
 4# 1. Create the GPIO object as
 5#    normal GPIO pin assignment 
 6p23 = machine.Pin(23, machine.Pin.OUT)
 7p22 = machine.Pin(22, machine.Pin.OUT)
 8
 9# 2. Create the servo object and
10#    attach the pwm driver to the GPIO pin
11b_servo = machine.PWM(p23)
12s_servo = machine.PWM(p22)
13#    Initialize the servo object with
14#    20ms pulse interval and set the
15#    angle to 0 degree
16b_servo.init(freq=50, duty=20)
17s_servo.init(freq=50, duty=20)
18
19# 3. Create a timer object for both servo
20timB = machine.Timer(0)
21timS = machine.Timer(1)
22#    Functions to handle the Timer callbacks
23def handle_timB(timer):
24    global is_timB
25    is_timB = True
26def handle_timS(timer):
27    global is_timS
28    is_timS = True
29#    and initialize the timer objects
30timB.init(period=200, mode=machine.Timer.PERIODIC, callback=handle_timB)
31timS.init(period=100, mode=machine.Timer.PERIODIC, callback=handle_timS)
32
33# Create a global variables
34is_timB = False
35is_timS = False
36b_angle = 0
37s_angle = 0
38
39# Functions:
40# Converts a value using map function of Arduino
41# this basically functions like by ratio and proportion
42def map(x, in_min, in_max, out_min, out_max):
43    return int((x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min)
44# Function to convert an angle to a duty value
45def servo(pin, angle):
46    pin.duty(map(angle, 0, 180, 20, 120))
47    
48# Main loop
49while True:
50    # Checks if the Timer interrupt sets the global variable
51    if is_timB==True:
52        is_timB = False         # disable the flag
53        servo(b_servo, b_angle) # rotate the servo
54        if b_angle < 180:       # if the angle is less than 180 
55            b_angle += 10        # increment the angle
56    if is_timS==True:
57        is_timS = False
58        servo(s_servo, s_angle)
59        if s_angle < 180:
60            s_angle += 5