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Re: How to handle USB Isochronous data Transfer?

Title: Re: How to handle USB Isochronous data Transfer?
I don’t quite understand what you mean with all of your math, but let’s assume it’s right...

The errors you get in the log are because you are trying to start the read on the current USB frame, which you can’t really do.  You need to do current frame + 1, or even better, current frame + 2.  In your second example, you are trying to start on current frame – 3934, which definitely isn’t going to work — that’s in the past.

Are you stepping through this code in the debugger?  What’s taking so long between when you get the current frame number and when you call Read()?  Do you control multiple devices with your driver, on different root hubs?  Every root hub gets its own current frame number, so if you get the current frame number from one hub, you can’t use it on another hub.

The Isoch frame too big error is because you’re asking for way too much data.  The max isoch packet in full speed USB is 1023, in high speed it’s 1024, so 3288 is way off.

Mark

On 2/25/05 6:04 AM, "Nakkala Sivaram Prasad" <email@hidden> wrote:

Dear all,
   Thank you very much Mr. Mark Cookson for your responce.
   As i mentioned already, in Alternate setting 3 Max Packet size of isochronous pipe is 300.
In different cases I've set the bytes per frame as 8/16, and No_Of_Frames as 32/64 randomly
Total requested data as 256 (8 * 32) / 1024 (16 * 64). In the above two cases i've seen the error
(-6907  Less Data than Buffer even though i alloted same size of buffer as requested data).
As per it is been suggested i've set bytes per frame as max packet size of the isoch pipe
(in the selected alternate setting 3). But that leads to system hang. So i've chosen
to set the bytes/frame as above.
   Then the USB Prober messages during USBIsocRead are

UIM    - Isoch transfer- WARNING! curframe later requested, expect some notSent errors! 0
UIM    - Isoch transfer- frameNumberStart: 129015
UIM    - Isoch transfer- curFrameNumber: 129015
UIM    - USBIsocFrame Ptr: 216152360
UIM    - Isoch transfer- First ITD: 2429120
UIM    - Isoch frame too big: 3288
USL      - calling isoc handler because of error -50
USL    - errorCallBack 21
USL    - errorCallBack head of queue so callback 21
 
        I would like to know what is the reason for the above error ? why isochronous transaction
is not successful? I tried by setting first frame number two above the current frame number,
but at that time following messages were there.
UIM    - Isoch transfer- WARNING! curframe later than requested, expect some notSent errors! 0
UIM    - Isoch transfer- frameNumberStart: 108136
UIM    - Isoch transfer- curFrameNumber: 112070
UIM    - USBIsocFrame Ptr: 21081744
UIM    - Isoch transfer- First ITD: 2428928
UIM    - Isoch frame not accessed. Frame in request(1 based): 1
UIM    - USBIsocFrame Ptr: 21081744
UIM    - ITD: 2428928
UIM    - Frames in this TD: 8
UIM    - Relative frame in TD (1 based): 1
UIM    - Current Frame: 112072
UIM    - Isoch frame not accessed. Frame in request(1 based): 2
   Does the number of frames in an Isochronus Read Call depends on usb device? If so, Is there
any way to find out the number of frames other than the trail and error method?
Thank u very much for your suggestions and replies.
With regards and thanks,
Sivaram Prasad Nakkala
Samsung Electronics India Ltd.,
Sec 81, Phase II
Noida - 201 305
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