add tinyusb stack to core folder

Author: hathach

README.md

@@ -131,7 +131,7 @@ Possible causes:
 
 To resolve this and enable 512 byte packets over USB serial, you must disable the
 Mass Storage Device interface on the JLink-OB, which will free up two of the 512 byte
-USB end points. (For details see [this article](https://wiki.segger.com/index.php?title=J-Link-OB_SAM3U).) 
+USB end points. (For details see [this article](https://wiki.segger.com/index.php?title=J-Link-OB_SAM3U).)
 
 You can do so by running `JLinkExe` from the command line, and then entering the
 `MSDDisable` command, and power cycling your nRF52DK. To re-enable MSD support, do the same
@@ -142,7 +142,8 @@ but enter the `MSDEnable` command.
 This core is based on [Arduino-nRF5](https://github.com/sandeepmistry/arduino-nRF5) by Sandeep Mistry,
 which in turn is based on the [Arduino SAMD Core](https://github.com/arduino/ArduinoCore-samd).
 
-The following tools are used:
+The following repos are used:
 
- * [GCC ARM Embedded](https://launchpad.net/gcc-arm-embedded) as the compiler
- * adafruit-nrfutil is based on Nordic Semiconductor ASA's [pc-nrfutil](https://github.com/NordicSemiconductor/pc-nrfutil)
+- adafruit-nrfutil is based on Nordic Semiconductor ASA's [pc-nrfutil](https://github.com/NordicSemiconductor/pc-nrfutil)
+- [tinyusb](https://github.com/hathach/tinyusb) as usb stack
+- [nrfx](https://github.com/NordicSemiconductor/nrfx) for driver

cores/nRF5/usb/tinyusb/LICENSE

@@ -0,0 +1,26 @@
+BSD License
+
+Copyright (c) 2018, hathach (tinyusb.org)
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+1. Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in the
+documentation and/or other materials provided with the distribution.
+3. Neither the name of the copyright holders nor the
+names of its contributors may be used to endorse or promote products
+derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
+EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.