ESP8266

1 概述

ESP8266 是一个带完整 WiFi 功能、 同时带一个 32bit MCU 的 SoC，可以取代原 Arduino 核心板 + WiFi 扩展板完成的大部分应用

最重要的，他的价格，只有 RMB 10 块左右

带 1MB Flash 的模块价格，也只在 RMB 13 块左右，批量的价格更便宜

ESP8266 的芯片详细特性，参考此页：ESP8266 特性

1.1 总体结构

ESP8266EX 集成：天线开关，RF balun，功率放大器，低噪放大器，过滤器，电源管理模块，32 位 MCU

仅需 7 个外围器件，就是一个完整的带 32bit MCU、完整 WiFi 功能的 SoC

ESP8266 结构框图：

内部 CPU (MCU) 使用 Tensilica’s L106 钻石系列32位内核处理器，带片上 SRAM

1.2 MCU 结构

Tensilica Xtensa LX3 32-bit RISC SOC clocked at 80 MHz，It can also reach a maximum value of 160MHz

Only 20% of MIPS has been occupied by the WiFi stack, the rest can all be used for user application programming and development

MCU Core 的框图：

• 32-bit ALU
• 16, 32 or 64 GPR
• six special purpose registers
• 80 base instructions

The Xtensa ISA employs 24-bit instructions with 16-bit narrow encodings for the most common instructions

1.3 SoC 内部存储

ESP8266EX WiFi SoC is embedded with memory controller, including SRAM and ROM. MCU can visit the memory units through iBus, dBus, and AHB interfaces.

According to our current version of SDK provided, SRAM space that is available to users is assigned as below:

• RAM size is around 50 KB, that is to say, when ESP8266EX is working under the station mode (WiFi) and is connected to the router, programmable space accessible to user in heap and data section is around 50 KB)

• There is no programmable ROM in the SoC, therefore, user program must be stored in an external SPI flash.