Using the WBX with UHD.
RX gain is controlled with a gain_group of wbx_rx_gain and usrp.adc.gain. wbx_rx_gain is controlled by GPIO connected to the RX attenuator (U302).
TX gain is controlled with a gain_group of usrp.dac.gain and wbx_tx_gain. wbx_tx_gain is controlled by AUX_DAC_A_TX connected to VCTL of the TX mixer (U501).
(draft) A gain group tries to accurately set the gain, by using multiple gain controls. First the raw distribution is attempted and later the remainder of the requested gain is resolved by adjusting the individual gain controls. This in order of priority. Highest priority is adjusted first.