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handling shortpacket with GPIFII | Cypress Semiconductor

handling shortpacket with GPIFII

Summary: 1 Reply, Latest post by Rover on 09 Apr 2013 12:10 AM PDT
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rskv's picture
Cypress Employee
1134 posts

Following are the ways to commit a short packet from GPIF II to USB:

Actually we have a action called COMMIT to submit a short packet. But we need to do IN_DATA action along with the COMMIT action. If we don't do IN_DATA then it will generate a Zero length packet after committing the short packet. But if you do IN_DATA then there is a chance that you may see extra data for one clock cycle. 

If you are seeing any extra data, then try changing the implemention as mentioned below:

Instead of doing COMMIT and IN_DATA actions in that state, do INT_CPU action. This will generate an interrupt to the firmware and there you can commit the short packet by calling CyU3PDmaChannelSetWrapUp API.


sai krishna.

Rover's picture
48 posts

If I use COMMIT in state machine, any short packet can be sent to USB. However, if I use INTR_CPU and call CyU3PDmaChannelSetWrapUp to commit the short packet, the size is trimmed  to multiple of 4. Why?

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