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Controlling the USB Transfer size
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Controlling the USB Transfer size

TimC posted on 06 Feb 2012 12:37 AM PST

1 Forum Post

 Hello,

how is the USB transfer size controlled through the FX3 API?

Do I understand correctly, that when using bulk transfers, packet size 1024 and 16x burst, the transfer size is always 16K? How can I increase it?

Can I increase it without having all the data available up front in a single buffer (but knowing it will stream in later)?

I searched the documentation and was not able to find anything pointing me at the USB transfer size.

Thank you

Tim




Re: Controlling the USB Transfer size

Chris R. posted on 06 Feb 2012 10:43 AM PST
Top Contributor
135 Forum Posts

Yes, in SuperSpeed mode the USB host can handle up to 16 packets with each 1024 byte in one chunk. But this is on driver level. On user level in Windows you can use larger transfer sizes. You can request for example 1MB data from the driver and the USB driver collect all the data if available. On FX3 side you can increase performance using multiple DMA buffers, default is 2 buffers. The FX3 can switch between the buffers very fast.






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