Migrating from XHRA to XU208

Sub forums for various specialist XMOS applications. e.g. USB audio, motor control and robotics.
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Re: Migrating from XHRA to XU208

Postby just280 » Thu Jul 19, 2018 5:02 pm

No luck programming the spi flash out of circuit. The XU208 still does not enumerate?
I just want to reiterate that my custom board closely resembles the circuit of the XK-USB-AUDIO-HPA board and has worked perfectly until I fitted the XU208, so I don't think PCB layout, USN traces or power will be an issue. I think I'm doing something stupid with the software compile. Does anyone have a compiled binary that will work on the XK-USB-AUDIO-HPA?
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Postby just280 » Wed Jul 25, 2018 1:20 pm

** Update **

Turns out that I had the 384K_EN tied high on my original circuit which is X0D06 pin on the XU208 used for boot configuration - need to be tied low for QSPI boot.
Circuit now enumerates on PC as 'xCORE-AUDIO Hi-Res 2' but my new problem is it won't stream audio!!!! If I go into sound properties on my PC the xCORE device has no properties to change like bit rate?

Any clues?
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Postby just280 » Wed Jul 25, 2018 3:26 pm

** Update 2 **

Installed the XMOS evaluation drivers and I get streaming... yey!
But why does it not work on the Microsoft native audio class 2 drivers of which the XHRA worked?
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Postby sleepfox » Wed Aug 08, 2018 5:35 pm

Hi, I have almost finished the PCB and have a few hardware questions before print.

1) What is the output impedance of XMOS and what is the correct resistance to source terminate the I2S signal ouput (target characteristic impedance of 50ohm)? 33ohm?

2) I plan to use XUF208 and thus do not need to use external spi flash. Therefore the 1-bit pin X0D00 is available. Can I use this for SPDIF output? I checked XUF208 document and it is not reserved. However, better check here with experts.

3) My pcb will be self-powered and will not use USB power. In this case, can I simply pull down the USB_VBUS pin to ground with a 47K resistor paralled with 0.1uf cap, WITHOUT connecting to the power pin of USB connector (through 10K cap and further paralled with 2uf cap)?

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Postby mon2 » Thu Aug 09, 2018 11:04 am

@sleepfox, please post your schematic and if possible the pcb layout in pdf format for a review before building the bare pcb.

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