| Author |
Message |
Guest
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 Posted:
Mon Dec 27, 2004 7:56 am Post subject:
USB NAK events continuously received |
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Hi,
Recently I have a project which needs to interface usbn9603 with MCU.
At PC side the XP can recognize the device as a HID device without
problem. However, I have traced the MCU program that it continuously
receive NAK events at end point 3. The endpoint 3 is enabled to
transfer data in initialization stage. However, I have not run any
program at the PC side.
Is it normal? Thanks! |
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Guest
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| Posted:
Fri Dec 31, 2004 4:59 am Post subject:
Re: USB NAK events continuously received |
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dereklai2k@yahoo.com.hk wrote:
| Quote: | Hi,
Recently I have a project which needs to interface usbn9603 with
MCU.
At PC side the XP can recognize the device as a HID device without
problem. However, I have traced the MCU program that it continuously
receive NAK events at end point 3. The endpoint 3 is enabled to
transfer data in initialization stage. However, I have not run any
program at the PC side.
Is it normal? Thanks!
|
Yes, it sounds like the host is polling according to the rate set in
the HID's endpoint descriptor. If the device isn't ready to return any
data to the host, it NAKs.
-a |
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Guest
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| Posted:
Fri Dec 31, 2004 7:56 am Post subject:
Re: USB NAK events continuously received |
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| If the device has no data, does it return NAK? |
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avrbasic
Guest
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| Posted:
Fri Dec 31, 2004 10:32 pm Post subject:
Re: USB NAK events continuously received |
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<dereklai2k@yahoo.com.hk> wrote in message
news:1104465893.815779.12610@z14g2000cwz.googlegroups.com...
| Quote: | If the device has no data, does it return NAK?
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sure!
if the device isnt ready to receive data or has 0 bytes to return, but is
otherwise functioning OK then NAK is proper response.
NAK is not an error response. it means - not yet, try again later.
endpoints that are disabled or not existant or not initialized should return
nothing
endpoints that have faults or beind set to STALL should return STALL
all other initialized, enabled and not in error endpoints should return NAK
well this dependant of the implementation and software etc..
Antti |
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