Hi all,
I created the system that 4k byte data is transferred through EZ-USB bulk transfer. FPGA (target side) create 4k byte data created and host side received data.
But we sometimes found that EZ-USB FX2 packet data is lost 512*N byte data. And packet reading time is sometimes takes 100msec or more. (usual case average is 16-17msec)
EZ-USB FX2 has two 512 byte buffer that is used as FIFO. I guess to have it overwritten unexpectedly.
This same experience that someone for?
And how you resolved?
The following are the details.
□ Environmental
FPGA: Actel APA-450-BG456
Driver: Windows almost as a sample using the Bulk Transfer
PC OS: WinXP
USB Target: 512byte * 2 FIFO memory used in
□ System Specifications
• USB Bulk Transfer
• Baud rate is about 2Mbps
• FPGA allows every 16msec burn data to create a 4K SRAM save nearly
• FPGA look at the USB Overflow flag Overflow if not designed to write data
• Host-side applications, a simple data earnestly Read
□ worrisome phenomenon
• The data of received at the host is 512*N bytes lost
• Read by the host, but sometimes time-consuming than the 100msec
□ Read the host side code
ResetEvent(h->overlappedIn.hEvent);
h->overlappedIn.Internal = 0;
success = ReadFile(h->handleIn,
pData,
maxLength,
pReadLength,
&h->overlappedIn);
if (!success) {
if ( GetLastError() != ERROR_IO_PENDING ) {
DebugVal("ReadFile Error = %d", GetLastError(), DEBUG_LEVEL_ERR);
return DEV_DEVICE_IO_ERROR;
}
}
waitResult = WaitForSingleObject(h->overlappedIn.hEvent,timeOut);
if (waitResult == WAIT_TIMEOUT) {
CancelIo(h->handleIn);
DebugMsg("ReadFile Error = WAIT_TIMEOUT", DEBUG_LEVEL_ERR);
return DEV_TIMEOUT;
}
GetOverlappedResult(h->handleIn,&h->overlappedIn,pReadLength,FALSE);
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