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Serial Audio Interface to EVAL-ADAU1777

Question asked by HonestEffort on Mar 15, 2018

I am attempting to bring up a serial audio interface to the EVAL-ADAU1777, and would like to post my approach and glean any advice or expertise from others who have blazed this trail.


Products from MiniDSP (such as the Ministreamer and USB streamer) have been mentioned in threads on this site as a good place to start. The Ministreamer is less expensive (~$35) while the USBStreamer is more configurable for higher-rate I2S data. The miniStreamer supports sample rates up to 96 kHz and has one stereo input and one stereo output, on either SPDIF or I2S. The configuration is unfortunately locked up by the manufacturer of the USB chipset. (Tenor). The USBStreamer supports sample rate up to 192 kHz and has ten input channels and ten output channels – two on TOSLINK and eight on I2S. Alternatively, 8 input and 8 output channels are supported via ADAT on the optical connectors.


I have selected the USBStreamer because I would like to be able to get the 24bit-192kHz sample rate. The USBStreamer always operates as a clock master, so I will need to follow the procedure outlined in the EVAL-ADAU1777 user guide to convert the board for external master clock MCLK input. This consists of installing a resistor (size and value not specified in the manual) across the unpopulated pads of R2, and removing the resistor R3 (which disconnects the onboard XTAL).


Question 0) Do I need to modify the board (remove R3, add R2) or is it sufficient to just operate MCLK normally but operate LRCLK and BCLK as slaves (as described here: ADAU1777(1772) stand alone codec. )


Question 1) What resistor value is recommended for R2?


Next, I have made a table of the proposed connections between the USBStreamer and the EVAL-ADAU1777. I am not using ADC_SDATA1 because it shares function with CLKOUT which I am using for my digital microphones.


Question 2) Are these connections (outlined in the attached table) correct?


Question 3) What settings need to be made on the "PLL & Clock Control" tab of the ADAU1777 hardware configuration to use an external MCLK?


Any advice from someone who has used a ministreamer or USBstreamer in the past is appreciated.