Hi all,
I am developing a driver for our TV receiver chip that connects a Windows CE
5.0 based product.
All related information as below:
Our TV receiver chip: USB client(USB 2.0 interface);
Windows CE 5.0 based product: USB host(EHCI host driver for USB 2.0);
Hardware platform: AMD DB1250 evaluation board with integrated USB 2.0 host
controller;
Software platform: Windows CE 5.0 with all QFEs up to date;
Data transfer mode: Isochronous read, 8 frames per transfer, 3 packets per
frame and packet size is 1KByte;

My problems is: after every transfer(24KBytes) there are about 10ms delay
(from Ellisys USB analyser), which caused a poor throughput. In theory, the
isochronous mode should archieve 24MByte/s(that is, 24KBytes/ms).

I read the EHCI driver code released with DB1250's BSP, but I cannot find
where the delay is. So I will be appreciated if someone gives me some hint.
Or if you have developed USB client driver with USB 2.0 interface, how about
your driver throughtput in the isochronous read mode on the Windows CE based
product.
I suspect maybe that delay is caused by Windows CE interrupt latency beause
it occurs after every transfer completes. But I don't how to measure the
latency.

Any advice is welcome. Thanks!

Code as below:
       for(dwFrameIndex = 0; dwFrameIndex < 8; dwFrameIndex ++)
       {
           dwFrameLength[dwFrameIndex] = 3*1024;
       }   

           dwErr = IssueIsochTransfer (pUsbTLG->UsbFuncs, pUsbTLG->IsochIn.
hPipe,
                                    DefaultTransferComplete, pUsbTLG->hEvent
[dwTotal],
                                    USB_NO_WAIT | USB_IN_TRANSFER |
USB_START_ISOCH_ASAP | USB_SHORT_TRANSFER_OK,
                                    0,                      // Using
USB_START_ISOCH_ASAP precludes the need for a start frame
                                    8,  // Number of frames to read
                                    dwFrameLength,             // Array that
receives the length of each frame
                                    pCurBufOut,              // Pointer to
transfer buffer
                                    0,                      // Specifies the
physical address, which may be NULL, of the data buffer
                                    &(pUsbTLG->dwBytesTransferred[dwTotal]),
// Number of bytes transferred by USB
                                    0,                   // Timeout in msec
                                    (LPDWORD)&(pUsbTLG->hTransfer[dwTotal]))
;              // Returns USB_ERROR or USB_TRANSFER