Mailing Lists: Apple Mailing Lists
Image of Mac OS face in stamp
 
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: USB Isochronous Pipe

Thank you - Will

give it a go ....


Jonathan Selby
Director - Software Development
Xaxero Marine Software Engineering Ltd
at skype.com - xaxjon
Satellite Phone (00) 88163 142 9922
Cell Argentina  (54) 929 0160 2064
(00) 64 (0)9 412 7580 fax (00) 64 (0)9 412 7579
http://www.xaxero.com
Software for extending your horizon....



魏立群 wrote: 
Hi Jonathan, Maruyama,

if you are programming for a usb 2.0 device then your trouble is that you are mixing up usb frames and usb microframes. In usb 2.0 frames are transfered to the device in microframes. Every usb frame contains 8 microframes.


err = (*intf)->ReadIsochPipeAsync(intf,ISO_PIPEREF,isoRequests [i].buffer,nextFrame,ISO_REQFRAMES,isoRequests[i].frames, isoCallback, &isoRequests[i]);

ReadIsocPipe takes usb micro frames as the numFrames argument; so what you are telling the system in this code is to transfer 1 ( !! ) usb frame!! That is too little and will fail. In my driver i usually transfer 128 usb frames ( that would be 128 * 8 microframes ). To

This means that every isoch read request include 1024 microframes, It is the same to:
#define ISO_REQFRAMES 1024
But I have tested that the frame list length should be little then 1000
I have read some code in IOUSBFamily, in file AppleUSBOHCI_UIM.cpp,
function AppleUSBOHCI::UIMCreateIsochTransfer,
This function will check numFrames that requested by one isoch read request, as the following:
if( (frameCount == 0) || (frameCount > 1000) )
{
//USBLog(3,
return kIOReturnBadArgument;
}
To the code list upper side, the max frame list reqeust length is 1000



make it even more confusing the currentFrame argument is in usb frames ( not microframes ). So your line


nextFrame+=ISO_REQFRAMES;

is also wrong for usb 2.0 because nextFrame should be in usb frames. nextFrame+=ISO_REQFRAMES/8 would be correct.

ReadIsochPipeAsync also has problems when you set the frStatus field wrong, ( especially in USB 1.1 ), even though i've seen bug fixes out there that claim that this problem was fixed. Try setting it to kUSBLowLatencyIsochTransferKey before sending the frames on the bus.

And one more idea: ReadIsochPipeAsync also returns an error if all frames have failed. On my device the first hundred frames just tend to fail so i just ignore the errors until i see that the stream is running. For instance, the usb controller will set the frStatus field to a non zero value if it noticed that not all bytes that were requested were really transferred ( and this happens quite often ). To make it more complicated: sometimes the error code of frStatus is a mac os x error code and sometimes it's the usb error code ( even though, again, apple claims to have fixed this problem, they apparently didn't ( not sure if this still occurs in the newest mac os x version ) ).

Please tell exactly which error code you are receiving.

Hope that helped

Greetings from Germany

Fabian

P.S: Oh yeah. As a general advice: update to the newest mac os x version. Some older versions really had problems with iso transactions.
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Usb mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/usb/email@hidden

This email sent to email@hidden


------------------------------------------------------------------------

_______________________________________________
Do not post admin requests to the list. They will be ignored.
Usb mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/usb/email@hidden

This email sent to email@hidden 
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Usb mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/usb/email@hidden

This email sent to email@hidden
References: 
 >Re: Re: USB Isochronous Pipe (From: Fabian Renn <email@hidden>)
 >Re: Re: USB Isochronous Pipe (From: 魏立群 <email@hidden>)



Visit the Apple Store online or at retail locations.
1-800-MY-APPLE

Contact Apple | Terms of Use | Privacy Policy

Copyright © 2007 Apple Inc. All rights reserved.