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Increasing size of EP0 Buffer | Cypress Semiconductor

Increasing size of EP0 Buffer

Summary: 2 Replies, Latest post by sodafarl on 20 Apr 2012 09:18 AM PDT
Verified Answers: 0
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wglados's picture
23 posts


Is it possible to increase the size of the EP0 buffer for FS and HS devices?


I see where it is set to 64 bytes in the USB descriptor C code.  Can we up it to something much larger, like 512 bytes?  We would like to be able to transfer larger chunks of data per vendor request.

RobK's picture
81 posts


I think, the USB-specification only allows EP0-sizes of:

LowSpeed = 8 Bytes

FullSpeed = 8, 16, 32, or 64 Bytes

HighSpeed = 64 Bytes

SuperSpeed = 512 Bytes



sodafarl's picture
133 posts


You should be able to send 65536 bytes per vendor request in HS and SS don't know what this is in FS. The host controller and driver in the computer will then divide this into the required USB packet sizes, 64 or 512. At the device end you will need a buffer big enough to hold the maximum transfer or if the buffer is smaller than the maximum transfer you will need some way to signal the host to hold off tranfers until the buffer is free again.


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