One 、 We are using DAP perhaps JLINK When downloading code , Sometimes there will be SWD/JTAG Communication Failure Mistakes and No Target Connected error

This problem is due to stm32 Upper SWCLK and SWDIO It's not turned on . Unconsciously used PA13 and PA4, These two feet are the decision swclk and swdio Reusable

------ As a result, the simulator cannot read stm32 Chip , This is the reason for the error report , although mdk Can recognize the emulator but cannot download the program .

There must be in your code AFIO Reuse this sentence .
At this time, your board can only be downloaded once , You can't download it when downloading , It can be called seal , So how to unseal it

Two 、 terms of settlement

At the beginning of learning 32 When there was no downloader , We will use this tool to download

Use this software to burn a random hex Program , Then back KEIL5 see

This time is good , You can download

summary

use FLYMCU Burning can be avoided JTAG/SWD burning , Restart the program and restart the MCU .