> 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.
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