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some question about USB
by Unknown on Mar 6, 2004 |
Not available! | ||
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According to the point :* The host can terminate a setup request before you have sent all that it
asked for. It will do this by sending status or a new Setup. Can i ask how should i treat the request in the setup stage if the host terminate it without entering status stage. For example , the host send me a setup commanding "Set_Address" or "Set_Configuration" , but then the host send me another setup token requesting another command instead of sending me a IN token for a Status stage. Should i still set myself a new address or new configured value in this case ? or should i treat the request terminated and doing nothing ? Also , if the host send me a reset after i have got a new address , should my device start from the beginning and listen to address 0 again ? Thank you very much for your listening . Regards, TOM
From: "Marc Reinig" mreinig@pacbell.net>
Reply-To: "Discussion list about free,open source USB IP core" usb@opencores.org>
To: "Discussion list about free,open source USB IP core" usb@opencores.org>
Subject: RE: [usb] some question abotu USB
Date: Fri, 5 Mar 2004 06:10:09 -0800
There is no defined sequence for a host to enumerate a device. It varies
from OS to OS and release to release. The key to success is to do whatever
the host asks and make sure your response complies with the spec. Do not
rely on any particular sequence.
Things to watch for:
* The host will often ask for more than you have got. Reply only with what
you have, never more.
* The host can terminate a setup request before you have sent all that it
asked for. It will do this by sending status or a new Setup.
* The host will often ask for less than you have. Make sure you only send
what it asks for.
* After the host sends a Set Address, make sure you are listening on the new
address. But, don't do this until after the end of the status phase. This
is the only Setup where you don't complete the request until after status.
All other you complete the request and then enter the status phase.
Marc Reinig
System Solutions
Windows Driver and Embedded Product Consulting
> -----Original Message-----
> From: KO TOM [mailto:tomko81@hotmail.com]
> Sent: Thursday, March 04, 2004 6:26 PM
> To: mreinig@pacbell.net; tomko81@hotmail.com
> Subject: RE: [usb] some question abotu USB
>
>
> Dear Marc,
>
> Thx for your reply, however , i do confused about the process of
> enumeration of USB device.
>
> I have read some books and documentation talking about the
> enumeration process, the steps are:
>
> 1. host - > reset
> 2. host -> request for device descriptors by default address 0
> 3. device -> responding with first 8 bytes of device descriptor
> 4. host -> reset
> 5. host -> set new address for device
> 6. host -> request for device descriptors with new address
> 7. device -> responding with all 18 bytes of device descriptor
> 8.host -> get configuration from device
> 9.host -> set configuration to device
>
> Is the above steps correct for USB enumeration? Is that OS will
> appear a "find new hardware" window after the above steps ? Any
> more reset step i have missed above?
>
> What I am confused is step 2 the first time host ask for descriptor:
> Will the host actually ask for 8 bytes of descriptor( the host
> should send out 80 06 00 01 00 00 08 00) or the host is actually
> asking for 18 bytes ( the host should send out 80 06 00 01 00 00
> 12 00) but we just return it with first 8 bytes?
> If we are returning 8 bytes descriptor, what should be the value
> of first byte of descriptor we return? 12H or 08H?
>
> In my mind, i guess the default max packet size should be 8
> before the host get our descriptor, so device can only send data
> packet with 8 bytes in step 2 but can return the whole descriptor
> ( 18 bytes) in a single packet in step 7.
> Am my guess right ?
>
>
> Also , USB1.1 and USB 2.0 are using the same hardware interface ,
> when the device is plugged into the usb bus, how can the host
> know it is running at 1.1 speed or 2.0 speed? (i mean slow, full
> and high speed in usb).
>
>
> Sorry for asking so much question, I am looking forward to
> hearing from you.
>
>
> Regards,
> TOM
>
>
_________________________________________________________________
¦b±zªº¦æ°Ê¸Ë¸m¤W¶Ç°e±µ¦¬ Hotmail ¶l¥ó¡A½Ã²¾¦Ü: http://zh-asiasms.mobile.msn.com
>From: "Marc Reinig" mreinig@pacbell.net>
>Reply-To: "Discussion list about free,open source USB IP core"
> usb@opencores.org>
>To: "Discussion list about free,open source USB IP core"
> usb@opencores.org>
>Subject: RE: [usb] some question abotu USB
>Date: Thu, 4 Mar 2004 07:32:19 -0800 > > >
> > -----Original Message-----
> > [mailto:usb-bounces@opencores.org]On Behalf Of KO TOM
> > Subject: [usb] some question abotu USB
>
> > 1. Is that only endpoint 0 can be a inout endpoint ?
> >An endpoint is the concatenation of the endpoint number and it's > direction.
>So, there can be two endpoints associated with a given endpoint
> number (an
>In endpoint and an out endpoint). When an endpoint is defined
> as an IN/OUT
>endpoint, it is really a pair of endpoints that share a common endpoint
>number. So, it is kind of a misnomer. However, since in common > practice,
>there is only one IN/OUT endpoint and that is the control
> endpoint, we just
>call it endpoint 0, when technically we should call it the
> IN/OUT endpoint
>pair of control endpoint number 0.
_______________________________________________
http://www.opencores.org/mailman/listinfo/usb
> >So, no, any endpoint number can be an IN/OUT endpoint. However, I have >never seen any device with more than one control endpoint. >
> > 2. If some of the endpoint , like endpoint 2, is using control
> > transfer . Can it be an inout endpoint ? > >It could, but why would you do this? >
> > 3. Due to the tree architecture of USB, is that my device can
> > recieve any packet on the usb bus ? I mean can my device (address > > 3)receive the packets sending to other device (address 2) ? Is > > that all packets are boardcasting? > >You will see all packets from the host, and none from other devices. |
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some question about USB
by Unknown on Mar 6, 2004 |
Not available! | ||
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-----Original Message-----
[mailto:usb-bounces@opencores.org]On Behalf Of KO TOM
Sent: Friday, March 05, 2004 5:57 PM
Subject: RE: [usb] some question about USB
According to the point :* The host can terminate a setup request
before you have sent all that it
asked for. It will do this by sending status or a new Setup.
Can i ask how should i treat the request in the setup stage if
the host terminate it without entering status stage. For example
, the host send me a setup commanding "Set_Address" or
"Set_Configuration" , but then the host send me another setup
token requesting another command instead of sending me a IN token
for a Status stage.
You abort the processing of the uncompleted Setup.
Should i still set myself a new address
No, because for a SetAddress, the action is done after the status stage. Since there would be no status stage, you would not change the address.
or new configured value in this case ? or should i treat the request
terminated and doing nothing ? The second Setup command aborts the first.
Also , if the host send me a reset after i have got a new address
, should my device start from the beginning and listen to address 0 again ? Of course, that's part of the definition of a RESET. Marc Reinig System Solutions |
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some question about USB
by Unknown on Mar 7, 2004 |
Not available! | ||
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Comments inline, all comments refer to the USB 2.0 spec.
-----Original Message-----
Subject: some question about USB
1. When the host send a "Get_Descriptor" command for the
configuration descriptor(80 06 00 02 00 00 FF 00), should I return the configuration descriptor itself only( 9 bytes) or followed by all the descriptor ( interface descriptor and endpoint descriptor) at the same data stage of the control transfer ? Per the spec (9.4.3), you return the configuration descriptor, the interface descriptors and endpoint descriptors.
2. It seems that the host will do a "Set_Configuration " in the
process of enumeration. Why is this "Set_Configuration" design for ? So you can have multiple configurations.
If i have two configuration 01 and 02 , then the host set
me up to 01 configuration , it seems that my 02 configuration can never be used. How are the host choosing my configuration based on? The responsible driver for your device selects and sets the configuration. In general, few OS's have supported multiple configurations.
3. The USB 1.1 specification point out that the interface
descriptor cannot be directly access by GetDescriptor() or SetDescriptor() , what if the host send out a GetDescriptor() with (80 06 00 04 00 00 FF 00), note that "04" at the fourth byte meaning for a interface descritor, should i handle this case ? This is not a valid command (9.4.3), so your host is sick and will die soon. If you get an invalid command, stall it.
4. When the host send out a GetConfiguration , should i just
return with a single byte in the packet ? Yes, the WLength word will be one, indicating you should return one byte.
5. At the electrial layer of USB , what it actual mean of Idle
state of the D+ D- lines? If just looking at their logic, for the full speed , is that mean D+ is 1 and D- is 0 ? If so , do idle state equal to J state? For full speed, yes. Also, no transitions on the bus. See Table 7.2.
6. Due to the tree topology of USB, all the device will recieve
any packet send out by the host , if the host want to send out a reset to device A and pull down the D+D- pin to low (SE0) for 2.5 us , then all the other USB device will misunderstand that the host want to reset them. How 's the host actually doing if it want to reset a particular device only? Do the HUB has the ability of filtering packet and signal ? It sends a command to the hub responsible for that port to reset that port. The traffic to the hub would be visible to all, but the reset would only be visible to anything connected to that port. Marc Reinig System Solutions |
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