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K-Type.md

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K-Type Bootloader

Since the K-Type was in development for so long, it has gone through a variety of changes. Due to the dual Type C connectors, additional logic is required inside the bootloader in order to determine which USB port is plugged in before starting the dfu code path. Much of Secure DFU was designed with the K-Type in mind. It is a mk20dx256vlh7 bootloader.

History

  • 2015 - Started work, much of the serial number, upload support and descriptor cleanup was driven by the K-Type
  • 2016 - Continued work
  • 2017 - Initial version, includes Secure DFU

Notes

  • The flash sector size of the mk20dx256vlh7 is half the size of the flexRAM store size (dfu.h:USB_DFU_TRANSFER_SIZE)
  • The K-Type has two USB ports, this requires the bootloader to scan which connector is plugged in.
    • This may result in the connection flapping if the OS is too slow
    • To aid in this, the flapping slows down on each try until a port is found
    • If both ports are plugged in, the first one to try the connection will get the USB connection.
      • If the USB port that received the connection is unplugged, the DFU will fail and the keyboard must be powered off before working again.

Specific Features

  • Debug LED turns on when in bootloader mode
  • Reset to firmware with Esc key (top left corner) switch S1
  • Dual Type C support for flashing firmware
  • Secure DFU

TODO

  • Nothing, unless there are requests