FX2LP empty IN control transfer

Question: When using the FX2LP, problem occurs when the host sends an IN control transfer with an empty size. On the FX2, such a transfer was legal, and was acknowledged properly by the FX2. With the FX2LP, empty IN control transfers are stalled by the FX2LP. Why is this happening?

 

Answer:

Please note that the FX2LP cannot have a Zero data for IN Vendor Requests and this is different from the FX2. You will have to modify the code to send an OUT Vendor Request with no data. This change has been done to make the EZ-USB FX2LP more robust in accordance with the protocol defined in chapter 8 and chapter 9 of the USB 2.0 Specification.