3. Timer Experiment

Routine Code

from machine import Timer 
import time

def on_timer(timer):
    print("Timer callback invoked")

timer = Timer(Timer.TIMER0, Timer.CHANNEL0,mode=Timer.MODE_PERIODIC, period=100,unit=Timer.UNIT_MS, callback=on_timer, arg=None)
last_time = time.ticks_ms()

try:
    while True:
        if time.ticks_ms() - last_time >= 200: 
            last_time = time.ticks_ms()
            print("Main loop")
except:
    timer.deinit() 
    del timer

Experiment Preparation

1. Connect the K210 to your computer via USB.
1. Open CanMV IDE and run the routine code above.

Experiment Results

1. After running, open the Serial Terminal at the bottom to view debug output. The timer prints every 100 ms and the while loop prints every 200 ms, so for each main loop message you see two timer messages.

Routine Code Explanation

1. Import the modules required to run the routine.

from machine import Timer 
import time

1. Define the on_timer callback function. When the timer triggers, this function runs and prints "Timer callback invoked".

def on_timer(timer):
    print("Timer callback invoked")

1. Create a timer instance.
  Timer.TIMER0 and Timer.CHANNEL0: specify timer 0, channel 0.
  mode=Timer.MODE_PERIODIC: periodic mode—the timer triggers repeatedly at the set interval.
  period=100 and unit=Timer.UNIT_MS: period is 100 milliseconds.
  callback=on_timer: set the callback function when the timer triggers.
  arg=None: no extra arguments passed to the callback.

timer = Timer(Timer.TIMER0, Timer.CHANNEL0,mode=Timer.MODE_PERIODIC, period=100,unit=Timer.UNIT_MS, callback=on_timer, arg=None)

1. Get the current millisecond timestamp with time.ticks_ms() and assign it to last_time for subsequent time comparisons.

last_time = time.ticks_ms()

1. Enter an infinite loop while True. On each iteration, compare the current timestamp with last_time. If the difference is at least 200 milliseconds, update last_time and print "Main loop". If an exception occurs during the loop, the except block runs: call timer.deinit() to stop the timer and release resources, then del timer to clean up.

try:
    while True:
        if time.ticks_ms() - last_time >= 200: 
            last_time = time.ticks_ms()
            print("Main loop")
except:
    timer.deinit() 
    del timer