MicroPython servo sweep on a Pico, signal on GP16

# Servo sweep: the servo on GP16 turns from 0 to 180 degrees and back, a
# degree every 15 ms. servo.py, in the next tab, turns an angle into the
# pulse width the servo reads.
import time
from servo import Servo

servo = Servo(16)

while True:
    for angle in range(0, 181):
        servo.angle(angle)
        time.sleep_ms(15)
    print("at 180")
    for angle in range(180, -1, -1):
        servo.angle(angle)
        time.sleep_ms(15)
    print("at 0")

# servo.py: a hobby servo on a PWM pin.
# The servo wants a pulse every 20 ms (50 Hz); the pulse's width picks the
# angle: 0.5 ms is 0 degrees and 2.5 ms is 180 degrees.
from machine import Pin, PWM

class Servo:
    def __init__(self, pin):
        self.pwm = PWM(Pin(pin))
        self.pwm.freq(50)

    def angle(self, degrees):
        degrees = max(0, min(180, degrees))
        self.pwm.duty_ns(500_000 + int(degrees * 2_000_000 / 180))