Hi,
You can download the KSDK standalone version for the TWR-K21F120M from HERE under the tab Software Development Kits.
The KSDK includes examples for different USB classes, following the path: C:\Freescale\KSDK1.1.0_K21FA_1.0.0\usb\example\device
Please refer to the Integration of the USB Stack and Kinetis SDK document (C:\Freescale\KSDK1.1.0_K21FA_1.0.0\usb\doc) to know how to build an run the examples.
Hope this information can help you
Best Regards,
Adrian Sanchez Cano
Technical Support Engineer
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