Recent projects have two boards DEMO F405, and a 8M crystal, a 24M, so the tragedy occurred. . . .
MDK is recognized by JLINK device number, but does not recognize the port, the error message: No Contex-M SW Device Found.
After overclocking the chip level can be set by BOOT pin, modify the start address, then you can download the program a success.
Specific operation is as follows:
1. Locate the BOOT1 and BOOT0, the BOOT1 down, BOOT0 pulled up to 3.3V.
2. Re-download the program, brush FLASH.
3. BOOT0 again down the original state will OK it.