首先我们的前提是实践过我曾经写的关于micropython ESP32＋PCA9685 舵机转速控制【https://blog.csdn.net/mrjiale/article/details/81813439】

在这个基础上利用物联网的技术进行舵机控制，注重的是如何用MQTT进行通讯

当然我们要做的前提准备是：

硬件：esp32板子，pca9685板子，一个舵机

【其实无论是树莓派板子，还是esp8266，还是其他的能够运用mqtt通讯的板子原理是相通的】

首先确保你的esp32接上电源后自动连上wifi

教程参考【https://www.jianshu.com/p/0613f3f3f4ba】

在esp32上安装MQTT库：

import upip

upip.install('micropython-umqtt.simple')

这样umqtt.simple这个包就安装好了

教程参考【https://github.com/1zlab/1ZLAB_MicroPython_ESP32_Tutorial/blob/master/19_MQTT%E5%85%A5%E9%97%A8%E4%B9%8B%E9%A1%B9%E7%9B%AE%E5%AE%9E%E6%88%98/MQTT%E5%85%A5%E9%97%A8%E4%B9%8B%E9%A1%B9%E7%9B%AE%E5%AE%9E%E6%88%98.md】

硬件连接：

软件：win10系统，电脑已安装python3.5

使用Python 进行基于MQTT的物联网开发， 这就需要用使用pip3安装另外一个库 paho-mqtt：pip3 install paho-mqtt

电脑安装软件：mosquitto

【下载地址http://www.mosquitto.org/download/】

画重点：每次使用MQTT进行通讯的时候都要打开mosquitto服务

找到安装目录，然后在当前目录下 shift加右键用命令窗口打开cmd，输入mosquitto -v

这里还是得整理下我要做啥：我将会用电脑通过mqtt通讯方式与esp进行通讯，即打算用wifi控制舵机【这就可以扩大了，如果我用手机app控制那就是和智能家居的做法类似了】

贴代码：

esp32板子要上传的代码：

main.py

servo.py

pca9685.py

subscriber.py

[1 ] main.py

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

[ 2] servo.py

# -*- coding:utf-8 -*-

'''

基于PCA9685 I2C舵机控制模块对舵机进行控制的库

'''

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)

[ 3] pca9685.py

# -*- coding:utf-8 -*-

'''

PCA9685 I2C舵机控制模块的库

'''

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(', data)

data = ustruct.pack(', 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)

[ 4] subscriber.py

#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'

CLIENT_ID = 'ZIMO'

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)

把上面代码丢进esp32，通电esp就会自动运行代码【main.py】

电脑端：

打开一个cmd窗口运行mosquitto服务，

打开另外一个cmd窗口运行下面代码 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 默认打开端口

TOPIC_ID = 'mrjiale' # TOPIC的ID

# 创建一个客户端

client = mqtt.Client()

# 连接到服务器(本机)

client.connect(HOST_IP, HOST_PORT, 60)

message = 'start'

client.publish(TOPIC_ID, message)

print('SEND: {}'.format(message))

舵机0-180°之间循环转动，完毕。

【最后反正你也不会同样操作，理解原理即可，毕竟每个人用的硬件不一样。】