如何编辑代码，编出一段函数（变量x和y）使pwm的占空比随变量变化？下图为自己编写的程序，报错了

[x31y]

# PWM 控制例子
#
# 这个例子展示了如何使用OpenMV的PWM

import time
from pyb import Pin, Timer
int x
int y
x=0
while(x<39):
def ads(x)
    result=x/2+1
    return result
y=ads(x)

tim = Timer(4, freq=1000)
ch1 = tim.channel(1, Timer.PWM, pin=Pin("P7"), pulse_width_percent=x)
ch2 = tim.channel(2, Timer.PWM, pin=Pin("P8"), pulse_width_percent=y)
x=x+1
while (True):
    time.sleep_ms(1000)

[kidswong999]

import time
from pyb import Pin, Timer

tim = Timer(4, freq=1000) # Frequency in Hz
ch1 = tim.channel(1, Timer.PWM, pin=Pin("P7"), pulse_width_percent=0)

while (True):
    x = 50
    ch1.pulse_width_percent(x)