## PWM驱动舵机

舵机使用频率为50Hz，脉冲宽度cs 1.0 ~ 2.0ms的脉冲作为控制信号。下面是产生基本舵机位置中间时的输出控制脉冲。
<code python>
from machine                import Pin,PWM
import time

pwm = PWM(Pin(15))

pwm.freq(50)
pwm.duty_u16(4915)

</code>

舵机具有三个接线：

棕色：GND
红色：+4.5 ~ +6V
黄色：指令脉冲信号

计算Duty_16公式为：

duty_u16 = 1.5 * 0x1000/20
对应脉冲宽度与duty_u16之间的关系：

1	3277
1.5	4915
2	6554

<code python>
from machine                import Pin,PWM
import time

pwm = PWM(Pin(16))

pwm.freq(50)

for _ in range(100):
    pwm.duty_u16(3276)
    print("Out pulse width : 1ms")
    time.sleep(1)

    print("Out pulse with : 2ms.")
    pwm.duty_u16(6553)
    time.sleep(1)

</code>

### 来自Maker Pi 
<code python>
# This code controls one servos to move from 0 degree to 180 degree,
# then back to 0 degree, and repeats forever.
# ---
# Connection: 1x Servo ports at GP12. Take note on the polarity.
# ---
# Hardware:
# 1. Cytron Maker Pi RP2040 (www.cytron.io/p-MAKER-PI-RP2040)
#    - Any RP2040 boards should work too.
# 2. TS90A Micro Servo 3-6V (www.cytron.io/p-analog-micro-servo-9g-3v-6v)
#    - Any servo motors within the rated voltage of 3.6-6V. 
# ---
from machine import Pin, PWM
import time

# fine tune the duty cycle values to suit your servo motor
MIN_DUTY = 1600
MAX_DUTY = 8400

pwm = PWM(Pin(12))
pwm.freq(50)

while True:
    pwm.duty_u16(MIN_DUTY)
    time.sleep_ms(1000)
    pwm.duty_u16(MAX_DUTY)
    time.sleep_ms(1000)
</code>

Example2
<code python>
# This code controls all 4 servos to move from 0 degree to 180 degree,
# then back to 0 degree, and repeats forever.
# ---
# Connection: 4x Servo ports - from GP12 to GP15
# ---
# Hardware:
# 1. Cytron Maker Pi RP2040 (www.cytron.io/p-MAKER-PI-RP2040)
#    - Any RP2040 boards should work too.
# 2. TS90A Micro Servo 3-6V (www.cytron.io/p-analog-micro-servo-9g-3v-6v)
#    - Any servo motors within the rated voltage of 3.6-6V. 
# ---
from machine import Pin, PWM
import time

# fine tune the duty cycle values to suit your servo motors
MIN_DUTY = 1600
MAX_DUTY = 8400

servo1 = PWM(Pin(12))
servo1.freq(50)
servo2 = PWM(Pin(13))
servo2.freq(50)
servo3 = PWM(Pin(14))
servo3.freq(50)
servo4 = PWM(Pin(15))
servo4.freq(50)

while True:
    servo1.duty_u16(MIN_DUTY)
    servo2.duty_u16(MIN_DUTY)
    servo3.duty_u16(MIN_DUTY)
    servo4.duty_u16(MIN_DUTY)
    time.sleep_ms(1000)
    servo1.duty_u16(MAX_DUTY)
    servo2.duty_u16(MAX_DUTY)
    servo3.duty_u16(MAX_DUTY)
    servo4.duty_u16(MAX_DUTY)
    time.sleep_ms(1000)
</code>