> On 5/20/05, BryanW  wrote:
> > Hi,
> >
> > I have a laptop, and also have seen problems. I find that the USB ports
on
> > the laptop do not generate enough power for some of the USB -> Serial
> > adapters to work correctly. You get a device is not recognised, and the
> > adapter added as a "Unknown USB". I ended up getting a USB self powered
hub
> > and this got my laptop to detect the adapter correctly. On my Desktop
PC,
> > there was no problem.
> >
> > I have a Toshiba P10 by the way.
> >
> > It is not just USB to serial adapters, I have a Nokia datacable that has
the
> > same problem, which is annoying as I wanted to be able to use this for
> > connecting to the net to get my email while out, and an external powered
hub
> > is not practical for that :(
>
> I was going to say that the USB-Serial adaptor is probably breaching the
USB specs for drawing power, but
> seeing your last paragraph I suspect your laptop is either below spec (USB
ports should supply 100mA all the
> time, 500mA when it's asked for by the device) or it's been damaged and
isn't able to supply the current
> needed.  Any USB port should supply the power as I said, and the fact that
a hub sorts it out is the clincher
> that your laptop isn't.  I have seen devices that draw more than they
should, but since you have two
> non-functioning devices I think the finger points firmly at the laptop!
Sorry to be the bearer of bad news,
> but it looks like replacing that is the only way you can do what you want.
>
> Cheers,
>
>
> Howard Winter
> St.Albans, England

Hi,

I would have come to that conclusion too if, it wasn't for the fact that I
run a Wireless USB mouse, I use a WinTV USB card, all powered from laptop
USB and they all work fine. I also have a 5.1 speaker system that is powered
by the port and that works on the laptop too. :) I have also tried a USB
mouse with a cypress chip in it and that worked too.

We make our own programmer using an FTDI chip, which is basically a
usb->serial device and that works perfect.

Looking closely at the nokia datacable and the USB->Serial adapter they both
use a Prolific chipset. The plot thickens :) Its a pl2303 according to the
driver file. I will be checking their datasheets to see if I can see
anything. My wife has said that I'm becoming a bit over the top trying to
find the problem, but hey I'm an engineer and I need to know why :)

Bryan



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