USB Audio 2 Maximum Channel limitations

Discussions about USB Audio on XMOS devices
shaw
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USB Audio 2 Maximum Channel limitations

Post by shaw »

We are currently running the latest version of the Xmos USB audio 2.0 Reference design. The firmware is running on an XUF216-512. We currently use 6 ADC channels and 2 DAC channels. So we have made some modifications to the firmware. We would ultimately like to use 10 or more USB in/out and 10 or more ADC/DAC I2S channels. We would Support sample rates up to 192 kHz and S/PDIF.

1: Are there any special considerations or limitations in the firmware or timing (or hardware) that we must keep in mind to run this many channels?

2: What is the maximum number of channels that can be supported in this configuration.?

We are prepared to move to a larger device to support the pin count that might be required for all of these I2S pins.

Thanks for any help,


fabriceo
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Post by fabriceo »

Hi
the Usb 2.0 firmware is very easy to configure multiple USB channels (in and out) and multiple ADC (in) or DAC (out) or DSD
your main limitation is the USB bandwidth and number of 1bit port available on the Audio tile 0:
no problem to have 11 datalines +LR+BCLK+MCLK where dataline can be i2s or dsd or spdif input,
and the USB bandwidth limitation which is 1024bytes transmit or received 8000 time by second.
spdif output if any can be on tile 1
as an example on tile0 , I m using MCLK on 1G, and then 1ADEFHIJKLMNOP for 11 datelines + lr+bclk
shaw
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Post by shaw »

hi Fabriceo,

Thanks for the feedback. I've begun configuring USB in/out, I2S DAC/ADC and configuring pins to support I2S. Going good so far. I'll post back here any problems or successes that I run into, with bandwidth or any other issues.

Thanks,
shaw
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Post by shaw »

on the hardware side. We will be adding additional features and functionality that will require additional pins, channels and cores. Is their a recommended pathway to such a larger device that is supported for ease of porting the USB audio 2 reference design?
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Ross
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Post by Ross »

10 channels is the max at 192kHz for async mode. We would need to add the high-bandwidth EP functionality to lib_xud to support more channels at this sample-rate.