- removed obsolte txamp functions (re DAC enable sequence)
- reorderd TX enable sequence
- consolidated time keeping (ticks/time vs sample count)
  - added RX_ and TX_ prefixes for samples counts
  - added new data type rx_sample_cnt_t
  - renamed function to calc rx lag for more clarity
  - deactivated downsampling (locked feature, almost all steps made)

- dropped support for OLD TXB with MCP4551 (see ERRATA)
- added support for NEW TXB with AD5245
- added timeout for busy-waiting peripheral (UART, I2C, SPI) interaction; on timeout, the MB indicates an error state through LEDs
- updated AD5245 interface/driver to support two devices (distinguished through A0 bit)
- tweaked TX/RX switch sequencing

changed interface of txgain (appended Level, added function to obtain number of tx gain levels, added number of gain levels to ACI response