Timer interval units in unix port

[glennra]

I'm trying to get a roughly 1 second timer and noticed that in the unix port I need to use an interval about twice the value that I want; as demonstrated in the code below. The LVGL docs say that interval_ms is in milliseconds.

Am I doing it wrong?

# Standalone LVGL timer test
import time
import lvgl as lv
import lcd_bus
import task_handler

th = task_handler.TaskHandler(duration=5)

def test_timer_interval(interval_ms):
    #lv.init()
    tick_intervals = []
    last_tick = [None]
    ticks = [0]
    def timer_cb(timer):
        now = time.time()
        if last_tick[0] is not None:
            tick_intervals.append(now - last_tick[0])
        last_tick[0] = now
        ticks[0] += 1
        if ticks[0] >= 5:
            return -1  # Stop timer
        return 0
    timer = lv.timer_create(timer_cb, interval_ms, None)
    while ticks[0] < 5:
        lcd_bus._pump_main_thread()
        #time.sleep(0.01)
    print("Interval {}ms: {}".format(interval_ms, tick_intervals))
    avg = sum(tick_intervals) / len(tick_intervals)
    print("Average: {:.3f} seconds".format(avg))
    expected = interval_ms / 1000.0
    if 0.8 * expected < avg < 1.2 * expected:
        print("PASS: Timer interval {:.3f}s close to expected {:.3f}s".format(avg, expected))
        return True
    else:
        print("FAIL: Timer interval {:.3f}s not close to expected {:.3f}s".format(avg, expected))
        return False
    
if __name__ == "__main__":
    all_passed = True
    for interval_ms in (1000, 2000):
        if not test_timer_interval(interval_ms):
            all_passed = False
    import sys
    sys.exit(0 if all_passed else 1)

Interval 1000ms: [0.5172691345214844, 0.518096923828125, 0.5177628993988037, 0.5158021450042725]
Average: 0.517 seconds
FAIL: Timer interval 0.517s not close to expected 1.000s
Interval 2000ms: [1.028236865997314, 1.028933048248291, 1.031255006790161, 1.032834053039551]
Average: 1.030 seconds
FAIL: Timer interval 1.030s not close to expected 2.000s

[kdschlosser]

try this code and see if it's more precise.....

# Standalone LVGL timer test
import time
import lvgl as lv

lv.init()

start_time = None


def test_timer_interval(interval_ms):
    global start_time

    ticks = []

    def timer_cb(_):
        global start_time
        stop_time = time.time()
        # duration in millisecond resolution
        duration = (stop_time - start_time) * 1000
        start_time = stop_time
        ticks.append(duration)

    start_time = time.time()

    timer = lv.timer_create(timer_cb, interval_ms, None)
    while len(ticks) < 5:
        time.sleep_ms(5)
        lv.tick_inc(5)
        lv.task_handler()
    
    timer.pause()
    timer.delete()

    print(ticks)
    avg = sum(ticks) / float(len(ticks))
    print(f"Average: {round(avg, 2)}")
    

if __name__ == "__main__":
    all_passed = True
    for interval_ms in (1000, 2000):
        test_timer_interval(interval_ms)

paste the output to me so I can see what it's doing.

[kdschlosser]

Then try this code and paste the output to me.

# Standalone LVGL timer test
import time
import lvgl as lv

lv.init()

start_time = None


def test_timer_interval(interval_ms):
    global start_time

    ticks = []

    def timer_cb(_):
        global start_time
        stop_time = time.ticks_ms()

        duration = time.ticks_diff(stop_time, start_time)
        start_time = stop_time
        ticks.append(duration)

    start_time = time.ticks_ms()

    timer = lv.timer_create(timer_cb, interval_ms, None)
    while len(ticks) < 5:
        time.sleep_ms(5)
        lv.tick_inc(5)
        lv.task_handler()

    timer.pause()
    timer.delete()

    print(ticks)
    avg = sum(ticks) / float(len(ticks))
    print(f"Average: {round(avg, 2)}")


if __name__ == "__main__":
    all_passed = True
    for interval_ms in (1000, 2000):
        test_timer_interval(interval_ms)

[glennra]

Here's the the output.

$ ../lvgl_micropy_unix ../tests/test_timer1.py 
[999.8891353607178, 999.9518394470215, 1001.14107131958, 999.7029304504395, 1000.477075576782]
Average: 1000.23
[1999.908208847046, 2000.614881515503, 2000.399112701416, 2002.732992172241, 2000.152826309204]
Average: 2000.76

$ ../lvgl_micropy_unix ../tests/test_timer2.py 
[1004, 1000, 1000, 1001, 1000]
Average: 1001.0
[2000, 2005, 2000, 2004, 2002]
Average: 2002.2

Thanks for this. I should be able to figure it out now.

[glennra]

In my app I've made these changes and now the timer works as expected.

# took out this
#th = task_handler.TaskHandler(duration=5)

...

import time
def event_loop():
    while lv.screen_active(): # exit when the screen is closed
        lcd_bus._pump_main_thread()
        time.sleep_ms(5)

        # added this
        lv.tick_inc(5)
        lv.task_handler()

A remaining issue is that I can't figure out how to stop the timer, pause() and delete() don't do it.

[kdschlosser]

the task_handler module is to make things easier. It is by no means the best way to go about handling when to refresh the display. It is always going to be best if you call lv.task_handler and lv.tick_inc yourself when there is ample time in your program loop to do so.

[kdschlosser]

another function is lv.refr_now that you can use to simply update the display without running anything else that is built into LVGL. That function will simply update the display with new data.