Hi all I am new to USB and keil after studying keil Hid example and lots of forum posts,I modified the code to make it as I need. Now I am able to send 64 byte of code to\from PC from\to my device. The problem is that I can do it with USB_EVT_IN event but when I want to use USB_EVT_OUT the device sends nothing to host.the description is ok(tested with USBlyzer). another thing: I am a little bit confused about what are EPx IN\OUT really are, any lightening idea will be appreciated. finally,wanted to thank Tsuneo for all his great work in this area,his posts helped me and surely so many others,alot. Regards, Hessam