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ezusb.sys and cyusb.sys speed problem at windows xp | Cypress Semiconductor

ezusb.sys and cyusb.sys speed problem at windows xp

Summary: 2 Replies, Latest post by RSKV on 07 Oct 2012 11:28 AM PDT
Verified Answers: 0
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I--Will's picture
16 posts

 we are designing a camera, and the EZ-USB FX2LP is our data transfer method. But now there is a question for us, when we test the speed of the usb. The endpoint is always full, when we transfer the data at test.

we use asyn slave fifo mode to connect to fpga  and fpga put 8bit counter data to FX2; and speed is 12.5MHz*8bit=100Mbit/S

we use endpoint6 ISO-mode to transfer the data to PC.

And at PC we use ISO-Stream mode to read the data;

And we found that the data between to packet is not continuous, so we think that the endpoint6 is always full. if the USB speed is 480MHz,I think this thing  would not happen.

So I want know if this driver (ezusb.sys or cyusb.sys) can get the speed 480Mhz, if not , what is their the maximum-speed.

gaya's picture
Cypress Employee
578 posts



CyUSB.sys is high speed capable driver. But maximum bandwidth possible with Isochronous transfer is 24 MBps (3K Bytes in one microframe). What is the no: of packets/microframe that you have specified in the endpoint descripotr, and what is the endpoint size chosen?




rskv's picture
Cypress Employee
1134 posts

Please make sure that you are using the ISO transfers with multi packets per each microframe.

Also, I would recommend you to use Endpoint 2 so that you can configure it to use the entire 4K endpoint memory. (size=1K, quad buffer).


sai krishna.

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