使用USART实现对STM32F3xx系列微控制器的在线编程IAP

　　An important requirement for most Flash-memory-based systems is the ability to update

　　firmware when installed in the end product. This ability is referred to as in-application

　　programming （IAP）。 The purpose of this application note is to provide general guidelines for

　　creating an IAP application.

　　The STM32F3 microcontroller product family can run user-specific firmware to perform IAP

　　of the microcontroller-embedded Flash memory. This feature allows the use of any type of

　　communication protocol for the reprogramming process. The USART is the example used in

　　this application note. Additionally， it allows two methods to calculate CRC （software and

　　hardware）。 This possibility is new in the STM32F3 microcontroller product family.