Hi Stone:
Here is an application note (AN4370) describes USB DFU Bootloader for MCUs. Please refer to below link. But it is based on old usb stack.
https://www.nxp.com/docs/en/application-note/AN4370.pdf?fsrch=1&sr=3&pageNum=1
Regards
Daniel
Daniel,
thank you, does it means there really no the DFU reference code based on the latest SDK 4.1.1, so I have to do the DFU based on old stack?
Best Regards
Stone