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Message
From: M. AbuKhater<perocletos@y...>
Date: Thu Jan 27 09:36:27 CET 2005
Subject: [usb] Difference between full&low speed transceiver
Hardware problem is reasonable but u should check ur hardware before anything. try on several PCs.
also it is not that simple for HID devices to communicate with the host, probably someone else can help u more about that, but what I know that there is several protocol issues there , it is not possible that the logical level is inverted or not, because of the pull up resistor I told u about causes the USB to indicates the host that there is a LOWSPEED device connected to it.
regards
Abukhater
xianshic <xianshic@y...> wrote:
Thanks Abukhater.
>From USB Spec R1.1, in Table 7-1, the J and K states
for full-speed signaling are inverted from those for
low-speed signaling. in Figure 7-14. Downstream Port
Transceiver, additional logic is required to invert
signal polarity on data in/out when low-speed devices
are attached.
My device doing as a host controller and integrate a
full speed tranceriver but not include the invert
signal polarity logic. Some mouse connected and work
well, some failed. Because both them are standard HID,
maybe not OS issue, maybe a hardware issue.
I guess that the working well mouse have a transceiver
invert signal polarity by itself. Am i right?
Thanks!
--- "M. AbuKhater"
wrote:
> hello Xianshic
> well first off all there is no lowspeed transceiver,
> when u connect a low speed device, the host (root
> Hub) or the hub u are connecting the device to
> detects a lowspeed device and deals with it as a low
> speed.
> I guess what happened with u concerning the mouse, I
> think this is a different issue, check the OS may
> be!
> >From the hardware side, the difference is that low
> speed has the pull-up resistor on the D- line while
> the Full/Highspeed has the pull-up on the D+.
> many more details are distributed in the specs. u
> should go through it
> hope that helps
>
> Abukhater
>
>
>
> xianshic wrote:
> Dear All,
>
> Any one can tell me a detail difference between
> full&low speed transceiver, or give a reference
> documnet about this, or point out which chapter in
> USB
> spec talk about this?
>
> If i have a full speed transceiver in host end, can
> i
> connect a mouse to host and work properly? Actually,
> I
> did it and found some work, but some failed.
>
> Thanks for your help!
>
> xianshic
>
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