I am new to deal with USB controller. When I followed application notes AN65974 to try loopback example using synchronous slave fifo interface, I found a problem. When I using Control Center to transfer 1024 bytes from PC to FPGA by Transfer File Out, the whole loop worked well. However, if I trying to transfer a few bytes of data (such as 8 bytes) from PC to FPGA, then data cannot be transferred back. The error code is 997.
I want to know where is the problem? And may I do some modifications on the loopback firmware to allow me to send few bytes to FPGA?
The loopback should work for small chunk of bytes as well. If it doesn't can you make sure that the PKTEND signal is being properly connection. (This is the signal which marks end of transfer for short transfers from FPGA to FX3).