About no cortex-m Device found in JTAG chain ... Problems that arise

These two days really survived, yesterday debugger broken, today can not download, appeared

No cortex-m Device found in JTAG chain.
Please check the JTAG cable and the connected devices, first of all, but also suspected that the debugger is a problem, but the morning the debugger bin file again downloaded again, specific download can refer to the previous article I wrote J-link Debugger does not light

Then, with the other minimum system board, found to be able to download, the problem can only be the smallest system board problem. To Google for the next reason, it is generally believed that: the JTAG pin as an I/O pin to use, the original JTAG function will certainly fail.

No matter what happens first, the solution is the first.

1. Find the BOOT1 and BOOT0, pull the BOOT1 low, BOOT0 pull up to 3.3V.

2. Re-download the program and swipe out of flash.

3. Pull the BOOT0 down again and the original state will be OK.

ST's Reference Manual is written in this way:

Looked for a long time, still do not understand why let it boot from the system once, and then from the user flash memory boot. The only idea is to let the program start from the system memory or to try to brush off the original program, so that the original disabled debugging interface failed to re-enable debugging. See the article's friends may wish to talk about their own ideas, hehe.

Http://bbs.ednchina.com/BLOG_ARTICLE_2115963.HTM