Added a README

README.md

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+# SushiBits One
+
+ARM Cortex-M in Arduino form fator, and consumes very little power.
+
+## Introduction & Goal
+
+This is one of my "design challenges" to myself:
+
+*   Arduino-compatible form factor,
+*   Take an 48-pin STM32 microcontroller (since STM32F103CBT6 are that cheap,)
+*   Bring all I/O pins out somewhere, be it the connectors, JTAG or USB,
+*   No two pins can be shorted together,
+*   Use only switch-mode power supply,
+*   Two layer PCB only,
+*   Single side load.
+
+## Main components
+
+*   STM32 microcontroller in LQFP-48 package. I have tested the following:
+    *   STM32F072C8T6 (Cortex-M0 @48MHz)
+    *   STM32F103CBT6 (Cortex-M3 @72MHz)
+    *   STM32L151CCT6 (Cortex-M3 @32MHz, ULP)
+    *   STM32F303CCT6 (Cortex-M4F @72MHz)
+    *   STM32F373CCT6 (Cortex-M4F @72MHz)
+*   WCH CH340B: USB to UART adapter.
+*   TI TPS562200: VIN to 5V buck converter.
+*   TI LM3671-3.3: 5V to 3.3V buck converter.
+
+## License
+
+This is [open source hardware](http://www.oshwa.org/), licensed under the
+[3-clause BSD license](LICENSE.md).