UART with mainboard works

- the sideboard can now send and receive Serial data from the mainboard
- fixed Processing sketch

README.md

@@ -74,14 +74,14 @@ make flash
 
 This firmware offers currently these variants (selectable in [platformio.ini](/platformio.ini) or [config.h](/Inc/config.h)):
 - **VARIANT_DEBUG**: In this variant the user can interact with sideboard by sending commands via a Serial Monitor to observe and check the capabilities of the sideboard.
-- **VARIANT_HOVERBOARD**: In this variant the sideboard is communicating with the mainboard of a hoverboard using the [FOC firmware repository](https://github.com/EmanuelFeru/hoverboard-firmware-hack-FOC). This Variant is not yet fully tested!
+- **VARIANT_HOVERBOARD**: In this variant the sideboard is communicating with the mainboard of a hoverboard using the [FOC firmware repository](https://github.com/EmanuelFeru/hoverboard-firmware-hack-FOC).
 
 Of course the firmware can be further customized for other needs or projects.
 
 ---
 ## 3D Visualization Demo
 
-By [converting Quaternions to Euler angles](https://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles), we can make a [3D visualization example](/docs/sketch_processing/sketch_processing.pde) in [Processing](https://processing.org/) as shown below. For this Demo VARIANT_HOVERBOARD was used.
+By [converting Quaternions to Euler angles](https://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles), we can make a [3D visualization example](/docs/sketch_processing/sketch_processing.pde) in [Processing](https://processing.org/) as shown below. For this Demo VARIANT_DEBUG was used.
 
 ![sketch_pic](/docs/pictures/sketch_processing_pic.png)