USB interface firmware failed to restore/upgrade



I have a RBL_Nrf51822 develop board, I accidentally erase the USB IF of MK20 and try to restore it, after hours of search I found there’s a bin file called “DAPLink_MK20_RBL_nRF51822.bin” and I follow the instructions in this page([](http://RBL githug)) drag and drop the bin file to the “BOOTLOADER” drive of my PC, and see the LED is
slow flashing, then I unplug/re-plug the USB cable, but the driver name never shows up.

Did I pick the correct bin file for my dev. board? Or anything I did wrong in the upgrade process?



The interface firmware file: