如何定时500毫秒串口发送数据

[e1hr]

如何定时500毫秒串口发送数据，Timer类给的示例运行不成功

[kidswong999]

import sensor, image
import pyb

sensor.reset()
sensor.set_pixformat(sensor.RGB565)
sensor.set_framesize(sensor.QVGA)
sensor.skip_frames(time = 2000)

last_time = pyb.millis()

while(True):
    img = sensor.snapshot()
    if pyb.millis() - last_time > 500:
        last_time = pyb.millis()
        print('send')
        

[e1hr]

你好，试了一下这个定时500ms会因程序周期变化而变化，中断定时给其它单片机通讯改怎么写呢？谢谢！！！

[kidswong999]

import time
from pyb import UART
from pyb import Timer

uart = UART(3, 19200)
data_bytes = b'123456'
# we will receive the timer object when being called
# Note: functions that allocate memory are Not allowed in callbacks
def tick(timer):
    global data_bytes
    global uart
    print(data_bytes)
    uart.write(data_bytes)


tim = Timer(2, freq=2)  # create a timer object using timer 2 - trigger at 1Hz
tim.callback(tick)  # set the callback to our tick function

while True:
    data_bytes = b'123456'
    time.sleep_ms(1000)
    data_bytes = b'654321'
    time.sleep_ms(1000)