在软件编译无错误时点击下载按钮时第一次烧录成功，然后再次烧录就不行了，弹出如下错误
could not initialize target device please power cycle the board and try again和
error:flash download failed -target DLL has been cancelled，检测硬件晶振，复位，电源都正常，不知什么原因
在软件编译无错误时点击下载按钮时第一次烧录成功，然后再次烧录就不行了，弹出如下错误
could not initialize target device please power cycle the board and try again和
error:flash download failed -target DLL has been cancelled，检测硬件晶振，复位，电源都正常，不知什么原因
