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README.md

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+openthread_nrf52_arduino(ot-arduino)
+======================================
+
+original [README.md rename to BlueFruit_nRF52.md](BlueFruit_nRF52.md)
+
+ot-arduino is a arduino package for nRF52840 that integrated with openthread subsystem.
+This package provides API that is able to communicate by OpenThread protocol.
+
+Installation
+--------------
+
+Add https://soburi.github.io/openthread_nrf52_arduino/package_soburi_otnrf52_index.json as an 'Additional Board Manager URL' in Arduino property.
+And install from Borad Manager.
+
+Requirements
+--------------
+
+MSYS2 (make, cmake) C:\msys2
+nrfjprog
+J-link adapter
+
+Limitation
+-------------
+
+Currently, Need J-Link adapter to upload binary.
+(Not implement DFU yet.)
+libtool seem to can't handle long path name.
+Set build.path to short path name property in preferences.txt.
+(It checked work correctly with "C:\ArduinoBuild".)
+
+Libraries
+---------------
+
+### OpenThread library
+
+OpenThread library provides two type of api.
+
+#### High Level API
+
+The High Level API provides a function with the same name as the CLI command.
+
+Each CLI command implements as function that name is same as command.
+Thus, it can use like a script on arduino code.
+
+#### LowLevel API
+
+Low Level API is a wrapper function of openthread api that enclosed otrLock() and otrUnlock().
+That ensure API can execute without explicit exclusion.
+
+
+### Sockets Library
+
+arduino-esp32 has [Arduino style commnuication (WiFi) API](https://github.com/espressif/arduino-esp32/tree/master/libraries/WiFi/src) that suitable for porting to this package because built on same lwip stack as ot-rtos.
+This package provides Socket API that is ported from arduino-esp32's API.
+
+
+
+Design
+------------------
+
+This package forks from [Adafruit's Arduino Core for Adafruit Bluefruit nRF52 Boards](https://github.com/adafruit/Adafruit_nRF52_Arduino).
+And this package includes [ot-rtos](https://github.com/openthread/ot-rtos) that is executable openthread system integrated with FreeRTOS.
+Adafruit's implementation also uses FreeRTOS.
+So they can be integrated without much change.
+
+Internally, openthread process runs as FreeRTOS's task in ot-rtos, also arduino main loop is run as FreeRTOS's task in Adafruit's implementation.
+
+We only need to run concurrently these two tasks.
+The one is openthread task and the other is arduino main loop tasks.
+
+Happily, ot-rtos is well splitting application code, thus we can put arduino process into as application code.
+
+Most part of arduino process is left as Adafruit's implementation.
+It is contains creating arduino main loop task.
+
+Calling vTaskStartScheduler() was replaced by otrStart() because otrStart() is internally calls vTaskStartScheduler().
+openthread task is created just before task scheduler started in otrStart().
+So two tasks runs concurrently by vTaskStartScheduler() calls.
+
+Build process
+--------
+
+Arduino has unique build system that far from cmake which is used from ot-rtos.
+This package is built by bit tricky way.
+Glue tool (it executable named [intiki](https://github.com/espressif/arduino-esp32/tree/master/libraries/WiFi/src), all "trick" is in it) gather command line arguments that is invoked from arduino-builder.
+Tool generate CMakeList.txt after all build command is run through and run build process.
+
+