Devbugfix UART buffer cleaning:
In the previous version a buffer cleaning function was used which resets the ringbuffer read index. As result the processing of data was stopped until the DMA write comes to the index 0. When reaching it the complete buffer was proceeded including possibly invalid data.
The usage of the cleanbuffer function was replaced by the flush buffer function (meaning the data is discarded but the data index is maintained). There was already a function for this. Because the function was 99% the same as the read function, it was integrated into the ReadData function. Calling the function with parameter flush = 1 will result in a buffer flush.
The workaround of the previous revision was updated to only be applied in case a DiveO2 sensor is operated in stand alone mode.
7 * an [STM32F427IIT6](http://www.st.com/content/st_com/en/products/microcontrollers/stm32-32-bit-arm-cortex-mcus/stm32-high-performance-mcus/stm32f4-series/stm32f427-437/stm32f427ii.html) as main processor. It is a Cortex-M4 processor with FPU, running at 180 MHz.
37 - **HAL_NVIC** _Nested Vector Interrupt Controller_: CORTEX IRQs used in `base.c` to handle buttons interrupts, in `gfx_engine.c` to manage VSYNC (screen's vertical sync) and in `stm32f4xx_hal_msp_hw2.c` to manage all other interrupts (ticks, DMA, DMA2D, TIM and USART).
40 - **HAL_SPI** _Serial Peripheral Interface_: implement the [standard SPI protocol](https://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus). Used to do full duplex communication between the two CPU in `data_exchange_main.c` to exchange dive settings and state, and in `externCPU2bootloader.c` to send firmware to _CPU2-RTE_.
42 - **HAL_UART** _Universal Asynchronous Receiver Transmitter_: serial communications used in `bonnexConnect.c`, `ostc.c`, `stm32f4xx_hal_msp_hw2.c`, `tCCR.c`, `tCpmm.c` and `tDebug.c`
47 - **HAL_DMA** _Direct Memory Accelerator_: automated memory transfers, used to manage SPI reception and transmission channels when communicating to main CPU.
50 - **HAL_I2C** _Inter-Integrated Circuit_ [bus controller](https://en.wikipedia.org/wiki/I2C) is another standard bus, used to connect the pressure sensor in `pressure.c`, the magnetic compass in `compass.c` and the battery state in `batteryGauge.c`. Initialisations are in `baseCPU2.c` and `stm32f4xx_hal_msp_v3.c`.
51 - **HAL_NVIC** _Nested Vector Interrupt Controller_: CORTEX IRQs used in `baseCPU2.c` to handle clock ticks, buttons and wireless state. In `spi.c` to know end of SPI transmissions. And in `stm32f4xx_hal_msp_v3.c` to setup various _I2C_ interupts.
55 - **HAL_SPI** _Serial Peripheral Interface_: implement the [standard protocol](https://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus). Used to do full duplex communication between the two CPUs. In `spi.c`, SPI1 is used to communicate to the maon CPU, and SPI3 to commicate to buttons.
