STM32 cannot download the program again after downloading it once, and the program cannot run.

Preface

As a result of taking over a new project in the laboratory , It is necessary to rewrite the program based on the original hardware , So I started to use the original main control board , But in the process of use, it is found that Jlink After downloading the program once, the chip cannot be read , Can't download the program , The chip also stopped running the program , After a day's tossing , Finally, the problem was solved perfectly , So make a note of the problem , For your reference .

1. The phenomenon

Use J-link After downloading the program once, you cannot download the program again , Chip stop .

2. Various solutions

2.1 Solution one . modify BOOT0 Pin

After looking for a lot of information on the Internet, I found that some posts said it might be a chip SWCLK and SWDIO The state of the pin has been changed .
General chip SWCLK and SWDIO All pins are connected to one 10k Resistance grounding of , To achieve FLASH start-up .
The solution is ：
1. take BOOT0 pull up
2. Press the manual reset button
3. take BOOT0 At ground
After I did this, I found that I couldn't read the program , But in BOOT0 You can read the chip when you pull it up , But I can't download the program .

2.2 Solution two . use ST-link Utility

use ST-link Utility To erase the program in the chip , link ：

https://blog.csdn.net/weixin_49805374/article/details/116604048?utm_medium=distribute.pc_relevant.none-task-blog-baidujs_title-1&spm=1001.2101.3001.4242

But during the operation, it is found that , The chip simply cannot be connected to ST-link Utility, After many attempts, it is found that the chip can be connected by pressing the reset key during the process of connecting the chip , In the process of erasing the data of the chip, the key reset device is also required , And then I was surprised to find that Jlink Can read chip data , And you can download the program , I thought the problem was solved in this way , however Found behind The program can only be downloaded once , And the program can not run after downloading , And no access to hardware emulation , You can only enter the simulation after pressing the reset key , And the program is running to systikclock（） Then it got stuck , So I doubt the problem of Shi Jingzhen , After inspection, it was found that the original plate was welded with 25M Crystal oscillator .

3. The real solution

The reason for the problem is that the board is welded with 25M Crystal oscillator , and STM32 In the official firmware 8M The crystal of , So in stm32 Just modify it in the official firmware of .

3.1 modify STM32 Crystal oscillator parameters in official firmware

3.1.1 stay stm32f4xx.h in take HSE_VALUE The parameter of is changed to 25000000

3.1.2 stay system_stm32f4xx.c No 316 Yes PLL_M It is amended as follows 25

So this perfectly solves the problem .