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Auxiliary Analog Input/Output Channels

There are 8 Auxiliary analog input channels connected to low speed 10 bit ADC inputs (labeled AUX_ADC_A1_A, AUX_ADC_B1_A, AUX_ADC_A2_A, AUX_ADC_B2_A, AUX_ADC_A1_B, AUX_ADC_B1_B, AUX_ADC_A2_B, and AUX_ADC_B2_B) which can be read from software. These ADCs can convert up to 1.25MSPS and have a bandwidth of around 200 KHz. These analog channels are useful for sensing the RSSI signal levels, temperatures, bias levels, etc.

Additionally, there are 8 analog output channels connected low-speed 8bit DAC outputs. These are AUX_DAC_A_A, AUX_DAC_B_A, AUX_DAC_C_A, AUX_DAC_A_B, AUX_DAC_B_B and AUX_DAC_C_B. These DACs can be used for supplying various control voltages such as external variable gain amplifiers control. In addition, there are two additional DACs (labeled AUX_DAC_D_A and AUX_DAC_D_B) which are constructed using 12 bit sigma-delta modulator with external simple low pass filter.

The USRP motherboard connectors (RXA and TXA) share one set of the 4 analog output channels (AUX_DAC_A_A to AUX_DAC_D_A for RXA and TXA) and each have 2 independent analog input channels (AUX_ADC_A1_A and AUX_ADC_B1_A for RXA and AUX_ADC_A2_A and AUX_ADC_B2_A for TXA). The RXB and TXB share their other own independent set. There is also AUX_ADC_REF which can provide a reference level for gain setting if it is necessary.

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