It has been reported that OpenSDA v2/2.1 bootloader could be corrupted when the board is plugged into a Windows 10 machine. An updated OpenSDA bootloader that fixes this issue is available at www.NXP.com/openSDA. There is also a blog article by Arm addressing this issue.
To reprogram the bootloader on affected boards, you will require an external debugger, such as Segger JLink or Keil ULink programmer attached to the JTAG port connected to the K20 OpenSDA MCU. For your convenience, the binaries of the OpenSDA v2.2 bootloader is attached at the bottom of this post.
If using a Segger JLink, download the latest JLink Software and Documentation pack and use the following JLink.exe commands to connect to the K20 OpenSDA MCU:
- Connect
- MK20DX128xxx5
- S
- 4000

And then use the following commands to reflash the bootloader:
- erase
- loadbin <your Bootloader Binary> 0x00000000

Here is another post on how to recover bricked OpenSDA boards and to prevent it getting re-bricked.
To check more information regarding OpenSDA on your boards, please go to www.nxp.com/opensda.