Yes, you are right Wouter, always forget that with RS232 we do not usually
use a protocol, just the plain wire :-) So yes, USB uses a huge overhead but
Olin, you said you use bulk transfer, which is supposed to be the fastest as
long as there is no other devices interrupting the channel. You use full
speed, so it's 12Mbps (even low speed with 1.2MBps is 10 times faster than
115Kbps) so full speed is 100x faster than that which means even with the
large overhead with bulk transfer you can download largish blocks from the
PC so that the overhead become relatively smaller I suppose -- I just could
not understand why is that slower and would like to know to learn how to
make faster USB devices?

Thanks,
Tamas


On 12/7/06, Wouter van Ooijen <wouter@voti.nl> wrote:
>
> > Yes, that is not that much. But I thought a USB communication
> > is faster than serial?
>
> (olin will probably answer specific to his proggers, but I can't resist)
>
> - communication speed matters only when it is an important aspect.
> speeding up the fastest step in a process will not have much overall
> effect.
> - speed is not the only metric for a communication channel. latency is
> another one, especially for a protocol that was originally designed for
> a channel (RS232) that has a very low latency (especially compared to
> its speed).
>
> Wouter van Ooijen
>
> -- -------------------------------------------
> Van Ooijen Technische Informatica: www.voti.nl
> consultancy, development, PICmicro products
> docent Hogeschool van Utrecht: www.voti.nl/hvu
>
>
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