First meeting

Discussions about USB Audio on XMOS devices
sparkJulio
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Joined: Mon Oct 21, 2024 3:14 am

First meeting

Post by sparkJulio »

Hello,
I know that the XS1 has been discontinued, but I was given a board by a colleague to get to know the platform before purchasing more recent models.

Just a few general basic questions about XMOS:
  • Is it possible to use all 1-bit ports for SPDIF I/O? Or is it mandatory to use I2S channels, and is SPDIF just a copy of I2S channels?
  • Is the latest XS1-compatible reference design 6.15.2? And the latest version of Xtools?
best regards
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Ross
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Post by Ross »

The design supports 1 S/PDIF output by default. You could add more transmit fairly easily. Having more than 1 receive would be problematic due to clocking implications.

The channels are customisable - they can be a copy or separate channels

Yes, 6.15.2 was the last official full release that supported XS1

(mod edit: moved to USB Audio)
Technical Director @ XMOS. Opinions expressed are my own
sparkJulio
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Post by sparkJulio »

Ross wrote: Mon Oct 21, 2024 4:30 pm The design supports 1 S/PDIF output by default. You could add more transmit fairly easily. Having more than 1 receive would be problematic due to clocking implications.

The channels are customisable - they can be a copy or separate channels

Yes, 6.15.2 was the last official full release that supported XS1

(mod edit: moved to USB Audio)
Thanks for your reply.
I'm having a lot of fun :)

Just a few more questions:
If it's problematic to have more than 1 SPDIF receiver, could I use I2S followed by SPDIF RX like the DIR9001?
Is it better to have SPDIF output directly through the XMOS or is all I2S followed by SPDIF RX/TX IC's the best topology to implement?

regards.
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Ross
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Post by Ross »

sparkJulio wrote: Tue Oct 22, 2024 10:37 pm
Thanks for your reply.
I'm having a lot of fun :)

Just a few more questions:
If it's problematic to have more than 1 SPDIF receiver, could I use I2S followed by SPDIF RX like the DIR9001?
Is it better to have SPDIF output directly through the XMOS or is all I2S followed by SPDIF RX/TX IC's the best topology to implement?

regards.
You can run multiple S/PDIF receivers on an xcore, that's no issue. The problem is each input will have its own independent, recovered clock (assuming they are not all coming from the same source..).
This is why most products don't support more than 1 digital input.

You'll have the same issue with multiple DIR9001 devices each outputting their own clock signals. You'd require sample rate conversion to deal with this, which you could add, but thats quite a bit of work.

An external IC that has S/PDIF -> ASRC -> I2S would make things easy (you can use an xcore do to this.. see https://www.xmos.com/file/an02003-spdif ... with-asrc/).

One issue with this is your S/PDIF streams will no longer be bit-perfect, so encoded streams are a no-go.

Multiple transmit is much easier as you don't have this clocking issue to worry about, the code changes would be trivial.
Technical Director @ XMOS. Opinions expressed are my own