I've been experimenting with the USB MSC code as we are working on a project where we want to store audio data on either a SATA SSD or USB flash drives. We are planning on using a C6748 as it has peripherals for both. I'm working on the LCDK6748 dev board and have the software from the starterware directory running and storing data to a USB flash drive now after enabling DMA mode. The throughput is quite low <100 kB/sec and it seems that there is a very long time between each byte/word transfer see the image below.
As you can see there is just over 480 nsec from the start of one transfer to the start of the next. I thought that a bulk transfer could be up to 1024 bytes long, but the system seems to be determined to transfer a byte at a time with the full USB packet overhead on each transfer. When I do this on another platform using Linux there is no dead time inbetween transfers. I'm rather new to the TI product suite and a little confused. Any suggestions on where to start looking? I've already read through the many posts on slow USB transfers, but there doesn't seem to be any conclusion. Is there some hardware limitation that causes this dead time? If so we will have to start looking for alternate parts.
Thanks,
Blair