Quick USB CRC5 question

[Michael Wakileh]

Hi! I'm trying to spend some time learning a bit about usb, and have been reading the cdc example...as well as some pages on the usb standard...

Now I have one question regarding the cdc example/virtual com ports:

Does the USB interface do CRC5 automatically?...
...and could one therefore omit using checksums on the virtual "serial" data trasmitted/received between pic and pc...

(unfortunately, I havent gotten around to reading Jan Alexson book)

[Darrel Taylor]

USB uses CRC5 for Token packets, and CRC16 for Data packets.
Upon error, a resend request tells the host/slave to send it again.

By the time it gets to one end or the other, you're pretty much guaranteed it's valid data.

[Michael Wakileh]

Thanks! That's nice to know...