在這個基礎上利用物聯網的技術進行舵機控制，注重的是如何用MQTT進行通訊

當然我們要做的前提準備是： 硬體：esp32板子，pca9685板子，一個舵機 【其實無論是樹莓派板子，還是esp8266，還是其他的能夠運用mqtt通訊的板子原理是相通的】

硬體連線：

軟體：win10系統，電腦已安裝python3.5

1. 使用Python 進行基於MQTT的物聯網開發， 這就需要用使用pip3安裝另外一個庫 paho-mqtt：pip3 install paho-mqtt
2. 電腦安裝軟體：mosquitto 【下載地址http://www.mosquitto.org/download/】 畫重點：每次使用MQTT進行通訊的時候都要開啟mosquitto服務
   找到安裝目錄，然後在當前目錄下 shift加右鍵用命令視窗開啟cmd，輸入mosquitto -v

這裡還是得整理下我要做啥：我將會用電腦通過mqtt通訊方式與esp進行通訊，即打算用wifi控制舵機【這就可以擴大了，如果我用手機app控制那就是和智慧家居的做法類似了】

貼程式碼： esp32板子要上傳的程式碼：

exec(open('subscriber.py').read(), globals())

# -*- coding:utf-8 -*-
'''
基於PCA9685 I2C舵機控制模組對舵機進行控制的庫
'''
import pca9685
import math

class
 
 Servos:
    def __init__(self, i2c, address=0x40, freq=50, min_us=600, max_us=2400,
                 degrees=180):
        self.period = 1000000 / freq
        self.min_duty = self._us2duty(min_us)
        self.max_duty = self._us2duty(max_us)
        self.degrees = degrees
        self.freq = freq
        self.pca9685 =
 
 pca9685.PCA9685(i2c, address)
        self.pca9685.freq(freq)

    def _us2duty(self, value):
        return int(4095 * value / self.period)

    def position(self, index, degrees=None, radians=None, us=None, duty=None):
        span = self.max_duty - self.min_duty
        if degrees is not None:
            duty = self.min_duty + span * degrees / self.degrees
        elif radians is not None:
            duty = self.min_duty + span * radians / math.radians(self.degrees)
        elif us is not None:
            duty = self._us2duty(us)
        elif duty is not None:
            pass
        else:
            return self.pca9685.duty(index)
        duty = min(self.max_duty, max(self.min_duty, int(duty)))
        self.pca9685.duty(index, duty)

    def release(self, index):
        self.pca9685.duty(index, 0)

# -*- coding:utf-8 -*-
'''
PCA9685 I2C舵機控制模組的庫
'''
import ustruct
import time


class PCA9685:
    def __init__(self, i2c, address=0x40):
        self.i2c = i2c
        self.address = address
        self.reset()

    def _write(self, address, value):
        self.i2c.writeto_mem(self.address, address, bytearray([value]))

    def _read(self, address):
        return self.i2c.readfrom_mem(self.address, address, 1)[0]

    def reset(self):
        self._write(0x00, 0x00) # Mode1

    def freq(self, freq=None):
        if freq is None:
            return int(25000000.0 / 4096 / (self._read(0xfe) - 0.5))
        prescale = int(25000000.0 / 4096.0 / freq + 0.5)
        old_mode = self._read(0x00) # Mode 1
        self._write(0x00, (old_mode & 0x7F) | 0x10) # Mode 1, sleep
        self._write(0xfe, prescale) # Prescale
        self._write(0x00, old_mode) # Mode 1
        time.sleep_us(5)
        self._write(0x00, old_mode | 0xa1) # Mode 1, autoincrement on

    def pwm(self, index, on=None, off=None):
        if on is None or off is None:
            data = self.i2c.readfrom_mem(self.address, 0x06 + 4 * index, 4)
            return ustruct.unpack('<HH', data)
        data = ustruct.pack('<HH', on, off)
        self.i2c.writeto_mem(self.address, 0x06 + 4 * index,  data)

    def duty(self, index, value=None, invert=False):
        if value is None:
            pwm = self.pwm(index)
            if pwm == (0, 4096):
                value = 0
            elif pwm == (4096, 0):
                value = 4095
            value = pwm[1]
            if invert:
                value = 4095 - value
            return value
        if not 0 <= value <= 4095:
            raise ValueError("Out of range")
        if invert:
            value = 4095 - value
        if value == 0:
            self.pwm(index, 0, 4096)
        elif value == 4095:
            self.pwm(index, 4096, 0)
        else:
            self.pwm(index, 0, value)

#created by lijiale

from umqtt.simple import MQTTClient
import time
from machine import I2C,Pin
from servo import Servos
i2c=I2C(sda=Pin(21),scl=Pin(22),freq=10000)
servos=Servos(i2c,address=0x40)

SERVER = '183.53.18.170'
TOPIC = b'mrjiale'


def servo_start():
	while True:
		for i in range(2, 170): 			 
			servos.position(0,i)  
			time.sleep_ms(10)     
		for i in range(170, 2, -1):
			servos.position(0,i)
			time.sleep_ms(10)

def mqtt_callback(topic, msg):
	global TOPIC
	print('topic: {}'.format(topic))
	print('msg: {}'.format(msg))
	if msg == b"start":
		servo_start()

client = MQTTClient(CLIENT_ID, SERVER)
client.set_callback(mqtt_callback)
client.connect()
client.subscribe(TOPIC)

while True:
	client.check_msg()
	time.sleep(1)

把上面程式碼丟進esp32，通電esp就會自動執行程式碼【main.py】

電腦端： 開啟一個cmd視窗執行mosquitto服務， 開啟另外一個cmd視窗執行下面程式碼 mqtt_servo.py

import paho.mqtt.client as mqtt
import time

HOST_IP = '183.53.18.170' # Server的IP地址
HOST_PORT = 1883 # mosquitto 預設開啟埠
TOPIC_ID = 'mrjiale' # TOPIC的ID

# 建立一個客戶端
client = mqtt.Client()
# 連線到伺服器（本機）
client.connect(HOST_IP, HOST_PORT, 60)

message = 'start'
client.publish(TOPIC_ID, message)
print('SEND: {}'.format(message))

舵機0-180°之間迴圈轉動，完畢。

【最後反正你也不會同樣操作，理解原理即可，畢竟每個人用的硬體不一樣。】