How to deal with USB pins on XL232 devices?

[CousinItt]

Hi all,

according to the data sheet for the XL232, it has some USB pins. Are these present because it's a knobbled XU232 without a USB controller?

Is there any guidance on what to do with these pins when USB isn't (and presumably can't be) used?

Thanks

[Redeye]

I've got a 3 x XL232 design where all of the USB pins are left floating. I can't honestly remember if this was what was recommended by XMOS when they reviewed the design.

[mon2]

Every article read so far (5+) on the net from assorted silicon suppliers and this topic states the same as Redeye has posted, just leave the USB D+/D- pins floating. The additional question is what to do with the voltage rails for the USB PHY, etc. I would leave room for just-in-case to power such pins. Better to ask XMOS through a support ticket to clarify and post your feedback here for future readers.

[Redeye]

On my design I've got power to the USB supply pins. Again, I can't remember if this was what was recommended by XMOS, but the schematic was checked by them before I got the board made.

[CousinItt]

Thanks mon2 and Redeye. I'll raise a ticket and post results here.

[CousinItt]

I posted a ticket. They said "post your question on the xcore support forum".

Still waiting...

[mon2]

Hi. We are reviewing a design with USB 2.0 hub controller and came across this topic of how to disable the USB port via straps.

While this may be an overkill for the XMOS CPU, it is an option to consider. Apply 0 ohm resistors to +3v3 to park the D+ and D- lines.

usb_hub_disable_port.png

[CousinItt]

Hi mon2 - sorry I missed your message. Thanks for the tip.

Still hoping someone from xmos might actually get around to answering this.