Detailed explanation of Wi-Fi module (ESP8266)

0. Wi-Fi module overview

The Wi-Fi module is a device for wireless communication, which can realize wireless data transmission and Internet connection between devices through Wi-Fi technology. The following is a detailed explanation of the Wi-Fi module:

1. Function: The Wi-Fi module is mainly used for wireless communication and connection between devices. It enables devices to transmit data, access the Internet, and communicate with other Wi-Fi devices over a Wi-Fi network. Wi-Fi modules are usually equipped with wireless receivers and transmitters, which can receive wireless signals from other devices or wireless routers, and send data to the target device or router.

2. Technical standard: Wi-Fi module complies with IEEE 802.11 wireless communication standard. Different Wi-Fi modules may support different Wi-Fi standards, such as 802.11a/b/g/n/ac/ax, etc. These standards define the frequency, transmission rate, security and other communication parameters of wireless signals to ensure interoperability between Wi-Fi devices.

3. Hardware composition: Wi-Fi modules are usually composed of wireless chips, antennas, RF front-ends, processors and memories. The wireless chip is the core component of the Wi-Fi module, responsible for processing the receiving and sending of wireless signals. Antennas are used to receive and transmit wireless signals. The RF front-end is responsible for signal amplification and conditioning. The processor and memory are used to execute wireless communication protocols, manage data transfers and store related configuration information.

4. Software support: Wi-Fi modules are usually equipped with embedded software to implement the Wi-Fi communication protocol stack, handle data transmission and manage network connections. These software are usually provided by vendors and can be configured and customized according to needs.

5. Power supply and interface: Wi-Fi modules are usually connected to an external power supply through power supply pins, and communicate with the main controller or other devices through interfaces such as UART, SPI, and I2C. These interfaces enable the Wi-Fi module to be integrated with various different types of devices.

6. Application fields: Wi-Fi modules are widely used in various Internet of Things (IoT) devices, smart homes, industrial automation, medical equipment, consumer electronics and other fields. They enable wireless connectivity, remote control, and Internet access to these devices.

1. Common Wi-Fi modules

1. ESP8266: ESP8266 is a low-cost, high-performance Wi-Fi module developed by Espressif Systems. It integrates Wi-Fi function and TCP/IP protocol stack, and can communicate with the main controller through the serial port. ESP8266 is widely used in IoT devices and DIY projects.
   

2. ESP32: ESP32 is a dual-core processor Wi-Fi module launched by Espressif Systems. In addition to the Wi-Fi function, ESP32 also integrates features such as Bluetooth, low power consumption, and various sensor interfaces, which are suitable for the Internet of Things, smart home, and industrial applications.
   

3. CC3x00 series: CC3x00 series is a Wi-Fi module launched by Texas Instruments, including CC3100 and CC3200 and other models. They feature low power consumption and high integration, making them suitable for applications such as IoT, home automation, and industrial control.
   

4. RN171/RN2483: RN171 and RN2483 are Wi-Fi modules launched by Microchip Technology. Their small size, low power consumption, and ease of integration make them widely used in IoT devices and sensor networks.
   

5. nRF24L01: The nRF24L01 is a low-power 2.4GHz wireless transceiver developed by Nordic Semiconductor that can be used as a part of a Wi-Fi module. It is suitable for applications such as remote control, sensor networks and wireless data transmission.
   

2. ESP8266 module

2.1 Concept

The ESP8266 is a very popular low-cost, high-performance Wi-Fi module. It integrates Wi-Fi function and TCP/IP protocol stack, and can communicate with the main controller through the serial port.
The following is a detailed explanation of the ESP8266 module:

1. Architecture and function: ESP8266 module adopts 32-bit Tensilica processor architecture, usually ESP8266EX chip. It integrates Wi-Fi wireless network connection function and TCP/IP protocol stack, and has reliable data transmission capability. ESP8266 also contains firmware for controlling, scheduling and managing network connections.

2. Wi-Fi function: ESP8266 supports 802.11 b/g/n wireless standard, and can operate as a Wi-Fi client or a Wi-Fi access point (AP). As a client, ESP8266 can connect to an existing Wi-Fi network to communicate with the Internet. As an AP, it can create its own Wi-Fi network, allowing other devices to connect to it and exchange data.

3. Communication interface: The ESP8266 module usually communicates with the main controller through a serial port (UART), using the AT command set as the communication protocol. The main controller can control Wi-Fi connection, data transmission and network configuration by sending AT commands to ESP8266. In addition to the serial port, ESP8266 can also communicate with other external devices through interfaces such as SPI and I2C.

4. Development environment and SDK: In order to facilitate developers to use ESP8266, Espressif Systems provides a complete set of development tool chain and software development kit (SDK). The SDK contains various APIs and function libraries for building applications, as well as tools for compiling, debugging and burning firmware. Developers can use C language or Lua scripting language for application development.

5. Firmware upgrade: The firmware of the ESP8266 module can be upgraded through the serial port to obtain new functions, fix bugs or improve performance. Espressif Systems releases new firmware versions frequently, developers can download and upgrade to the latest version from the official website.

2.2 Features

There are many models and variants of ESP8266 modules, such as ESP-01, ESP-12E, NodeMCU, etc., and the functions and characteristics of each model may be slightly different.

The following are some common features and usage precautions of the ESP8266 module:

1. GPIO pins: ESP8266 modules usually have several general purpose input output (GPIO) pins for connecting external devices and sensors. These pins can be configured as inputs or outputs and can be used to control external circuits, read sensor data, etc.

2. Network protocol support: ESP8266 supports TCP/IP protocol stack, which can implement common network protocols such as HTTP and MQTT. This enables it to communicate and exchange data with cloud service platforms, servers and other devices.

3. Low power consumption mode: ESP8266 module has a variety of low power consumption modes, which can save energy in different application scenarios. For example, it can go into sleep mode to reduce power consumption and wake up quickly when needed.

4. External memory support: ESP8266 modules usually support external flash memory (Flash) for storing application programs, firmware, and configuration data. This allows the modules to have large storage capacities to support complex applications and data processing.

5. Software Ecosystem: Due to its wide application and developer community support, ESP8266 has a rich software ecosystem. Developers can leverage various open source libraries, frameworks, and sample codes to quickly develop applications and get support and solutions from the community.

6. Power supply and size: The ESP8266 module is usually powered by 3.3V and has a small size and surface mount technology (SMT) package, which is suitable for integration into various types of electronic devices.

It should be noted that the ESP8266 module may generate a certain amount of heat during high-load network communication, so heat dissipation and temperature management need to be considered in the design. In addition, since the ESP8266 module uses a serial port for communication, the data transmission rate with the main controller may be limited, and performance evaluation needs to be performed according to application requirements.

3. The sample code of STM32F103C8T6 using ESP8266 for wireless communication

#include "stm32f10x.h"

// 定义串口1的GPIO引脚
#define USART_GPIO GPIOA
#define USART_TX_PIN GPIO_Pin_9
#define USART_RX_PIN GPIO_Pin_10

// 定义ESP8266的连接状态引脚
#define ESP8266_STATUS_GPIO GPIOA
#define ESP8266_STATUS_PIN GPIO_Pin_8

// 定义发送和接收缓冲区大小
#define BUFFER_SIZE 128

// 接收缓冲区
char rx_buffer[BUFFER_SIZE];
// 发送缓冲区
char tx_buffer[BUFFER_SIZE];
// 接收完成标志
volatile uint8_t rx_complete = 0;

// 串口1接收中断处理函数
void USART1_IRQHandler(void)
{
    
    
    if (USART_GetITStatus(USART1, USART_IT_RXNE) != RESET)
    {
    
    
        static uint8_t rx_index = 0;
        char data = USART_ReceiveData(USART1);
        rx_buffer[rx_index++] = data;
        
        if (data == '\n' || rx_index >= BUFFER_SIZE - 1)
        {
    
    
            rx_buffer[rx_index] = '\0';
            rx_index = 0;
            rx_complete = 1;
        }
    }
}

// 发送字符串到ESP8266模块
void sendToESP8266(const char* str)
{
    
    
    while (*str)
    {
    
    
        USART_SendData(USART1, *str++);
        while (USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
    }
}

int main(void)
{
    
    
    // 初始化USART1
    USART_InitTypeDef USART_InitStruct;
    GPIO_InitTypeDef GPIO_InitStruct;
    
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA, ENABLE);
    
    // 配置USART1的引脚
    GPIO_InitStruct.GPIO_Pin = USART_TX_PIN;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(USART_GPIO, &GPIO_InitStruct);
    
    GPIO_InitStruct.GPIO_Pin = USART_RX_PIN;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(USART_GPIO, &GPIO_InitStruct);
    
    // 配置USART1的参数
    USART_InitStruct.USART_BaudRate = 115200;
    USART_InitStruct.USART_WordLength = USART_WordLength_8b;
    USART_InitStruct.USART_StopBits = USART_StopBits_1;
    USART_InitStruct.USART_Parity = USART_Parity_No;
    USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
    USART_InitStruct.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
    USART_Init(USART1, &USART_InitStruct);
    
    // 使能USART1接收中断
    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
    NVIC_EnableIRQ(USART1_IRQn);
    
    // 初始化ESP8266状态引脚
    GPIO_InitStruct.GPIO_Pin = ESP8266_STATUS_PIN;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(ESP8266_STATUS_GPIO, &GPIO_InitStruct);
    
    // 启动USART1
    USART_Cmd(USART1, ENABLE);
    
    while (1)
    {
    
    
        // 检查ESP8266连接
            if (GPIO_ReadInputDataBit(ESP8266_STATUS_GPIO, ESP8266_STATUS_PIN) == Bit_SET)
    {
    
    
        // ESP8266已连接
        
        // 发送数据到ESP8266模块
      		if (rx_complete)
      		{
    
    
          		// 处理接收到的数据
          		// ...
            
           		// 发送数据到ESP8266
            	sendToESP8266(tx_buffer);
            
            	// 清空发送缓冲区
           		memset(tx_buffer, 0, sizeof(tx_buffer));
            
           		// 重置接收完成标志
          		rx_complete = 0;
      		}
  		}
  		  else
 		{
    
    
       		 // ESP8266未连接
       		 // 可以执行重新连接或其他处理
   	 	}
	}
}