NODEMCU introduction and use

NodeMcu esp8266-12E is based on open source IoT packaged boards.
Simple to use module debugging is very convenient and simple in the process of learning esp module.

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NodeMcu

ESP-12E is to use a few more modules on the package
(only NodeMCU V1 is using the ESP-12
as long as NodeMCU V2 or V3 ESP-12E is to use)
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The main parameters of

the pin diagram (Pin developers board without the GPIO GPIO not need to see the corresponding table)

ESP8266 chip 17 GPIO pins (GPIO0 ~ GPIO16). These pins are GPIO6 ~ GPIO 11 is connected to the flash development board (Flash Memory) is therefore not recommended GPIO6 ~ GPIO 11.

In this remaining 11 stitches in, there are two pins reserved for serial RX and TX.

Some GPIO pin while both the other functions, such as the RX, TX, SD2, SD3, as most of these GPIO pins are not used because they can be used in other processes.
Thus, only the last nine general-purpose I / O pins, i.e., D0 to D8.

Note that, D0 | GPIO16 as GPIO pins can only read / write and does not support any special features
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of voltage and current limit
NodeMCU development of input and output voltage limiting plate pin is 3.3 V. If more than 3.6V voltage is applied to the pin it may cause damage to the chip circuitry. Also note that these pins maximum output current is 12mA.

Since the pin NodeMCU Development Board allows the voltage and current are lower than the pin Arduino development board,

特殊引脚
GPIO2引脚在NodeMCU开发板启动时是不能连接低电平的。
GPIO15引脚在开发板运行中一直保持低电平状态。
GPIO0引脚在开发板运行中需要一直保持高电平状态。否则ESP8266将进入程序上传工作模式也就无法正常工作了

模拟输入
AD转换将模拟量转换为数字量只有一个引脚 A0，nodemcu上可以读取模拟输入0-3.3v的电压

通讯
串行端口（UART）TX（GPIO1）和RX（GPIO3）
以及 TX（GPIO2）和RX（GPIO8）

I2C
ESP8266只有软件模拟的I²C端口，没有硬件I²C端口。可以使用任意的两个GPIO引脚通过软件模拟来实现I²C通讯。ESP8266的数据表（datasheet）中，GPIO4（D2）标注为SDA，GPIO5（D1）标注为SCL。

SPI
ESP8266的SPI端口情况如下：
GPIO14 — CLK
GPIO12 — MISO
GPIO13 — MOSI
GPIO 15 — CS(SS)

安装驱动

需要安装驱动才能通过usb连接NodeMcu 电脑才能识别到端口
Windows ch341驱动下载
（v1使用ch341驱动 V2 与V3 大部分使用cp210x驱动）
cp210x驱动下载

arduino开发

环境搭建

在项目加载库库管理中搜索dht 下载DHT sensor by Adafruit （1.30）

2.打开工具开发板开发板管理器搜索esp8266 下载esp8266 by ESP8266 Community （2.4.2）

3.选择NodeMcu开发板

4.使用示例

上传会看到灯一亮一灭
联合mqtt使用
打开示例 pubsubclient中的mqtt_esp8266

(如果没有这个库可以到项目–> 加载库 —> 管理库里面进行下载)

else

基于NodeMcu的开发可以到这里进行学习 http://niehen.cn/category/esp8266/
参考 https://blog.everlearn.tw/nodemcu/%E7%AC%AC%E4%B8%80%E6%AC%A1%E8%B3%BC%E8%B2%B7-nodemcu-%E5%B0%B1%E4%B8%8A%E6%89%8B
参考
 esp8266ex技术规格书
 太极创客