xConnect, XUD, and the forbidden pins

[armands117]

Hi guys ! I'm starting an xmos project, and got a question...

Seems the use of XUD usb library deactivates quite a lot of pins on the chip, some of which are used for the xConnect debug link (2 bits link on XLA : X0D03-4-5-6).

In the USB audio XS1-L1 reference design, those pins are not connected.

However, in the Multichannel USB Audio (XS1-L2) reference design, those pins are connected.

So, I'm wondering if xConnect and xScope can be used, even if the datasheets says the pins are unavailable when using USB ?...

Or is JTAG the only way to debug when using usb ?

2 bit XLA works well for xscope on XS1-L1 device while using USB.

[armands117]

Good news ! What package are you using ?

I'm hesitating between TQ128 XS1L1 and QFN124 XS1L2. I won't really need the extra power, but could use the extra IO.

I am using both: TQ128 XS1L1 and QFN124 XS1L2 each for a different version of product.
With TQ128 XS1L1 IO (in my case inputs) is a scarce resource.

[armands117]

OK. Thanks for confirming that it works.

Nice to know I won't be debugging over a slow serial port.

Maybe the whole fast XLA link works then, who knows ? The docs say that using USB disables the ports, but since you say the link works, it must disable something, but not everything. Maybe it disables the ports, but not the mux that connects the pins to the XMOS link. Documentation bug ?

if not using X0D1 and X0D10 for SPI Flash 5 bit XLA might be available (I have not tested), i assume in USB mode it only uses internal machinery associated with ports (not with XMOS links) - not a documentation bug just an incompleteness.
All this USB stuff is well hidden and even bit 1 of Processor status register 0x02 that turns USB support on is not mentioned in "XS1-L System Specification" ;)

[segher]

Maybe the whole fast XLA link works then, who knows ? The docs say that using USB disables the ports, but since you say the link works, it must disable something, but not everything. Maybe it disables the ports, but not the mux that connects the pins to the XMOS link. Documentation bug ?

It should work. Neither the pins nor the ports are disabled, just the connection
between them is. The ports are routed to the UIFM instead, and the pins can be
used by the external xlinks as usual.

I distinctly remember this being documented _somewhere_, I don't remember
where though. Maybe the xlinks document?

[Folknology]

I think the IO on xrun is non standard and may have somewhat limited bandwidth. However given you are engineering usb in you could use vcom and /dev/ttyACM0 that would be fairly easy..

regards
Al