Add initial readme

Author: weliveindetail

README.md

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+# ez-clang-arduino
+
+This repository provides an Arduino-based reference implementation of the [ez-clang RPC and runtime interface](https://github.com/echtzeit-dev/ez-clang#documentation).
+The build processes is based on [PlatformIO](https://platformio.org/) and allows for quick adaptation.
+This is a good starting point for developing a compatible firmware for your own development boards.
+
+## Supported host machines
+
+Right now, build instructions are tested only on Intel x86_64 hosts running Ubuntu 20.04.
+If you get it to work on other systems, please document your steps and create a pull request.
+
+## Supported target devices
+
+For the time being, the [Arduino Due](https://docs.arduino.cc/hardware/due) development board acts as the reference hardware for ez-clang.
+It features an Atmel SAM3X8E ARM Cortex-M3 CPU (armv7-m) and has more than enough flash and RAM for typical purposes.
+If you get it to work with other boards, please share your patches.
+
+## Build
+
+Install and run [PlatformIO](https://docs.platformio.org/en/latest/core/installation.html#super-quick-mac-linux):
+
+```
+➜ python3 -c "$(curl -fsSL https://raw.githubusercontent.com/platformio/platformio/master/scripts/get-platformio.py)"
+➜ export PATH=$PATH:$HOME/.platformio/penv/bin
+➜ git clone https://github.com/echtzeit-dev/ez-clang-arduino
+➜ cd ez-clang-arduino
+➜ platformio run -e due
+...
+Replacing .pio/build/due/firmware.elf
+Relink succeeded
+Building .pio/build/due/firmware.bin
+```
+
+## Run
+
+Connect your board, upload the `firmware.bin` with [PlatformIO](https://docs.platformio.org/en/stable/core/quickstart.html#process-project) and 
+verify the serial output:
+```
+> platformio run -t upload -t monitor -e due
+...
+Verify successful
+done in 12.890 seconds
+Set boot flash true
+CPU reset.
+...
+--- Quit: Ctrl+C | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
+␁#W��W#␁j␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␀␅␀␀␀␀␀␀␀0.0.5P5␇ ␀␀␀␀�F␁␀␀␀␀␀␁␀␀␀␀␀␀␀␕␀␀␀␀␀␀␀__ez_clang_rpc_lookup�␀␀␀␀␀
+```