linux下ymodem协议下载工具源码，主要功能是配合stm32串口更新固件程序-Ymodem download the source code under the Linux protocol, the main function is to coordinate with the STM32 serial port to update the firmware

stm32通过iap实现远程升级固件，无需现场烧录。-stm32 by spi remotely upgrade firmware, without on-site programming.