USB VCP WIn7 driver has problems with 1024 byte payload

taraben · ‎2015-05-27

Posted on May 27, 2015 at 13:31

Hello,

I am using the latest Windows driver from 1.4 package. I am Working on Windows7-64bit. However it tells version 1.3.1.

My Project is based on CubeMx USB CDC.

My Problem is when I sent a payload with size power_of_2 then the driver does not forward data to PC application.

e.g.

I sent from uC CDC device 1024 byte - nothing happens in terminal program

then I sent 3 bytes from device - then the PC driver delivers the 1024 Byte as well as the 3 Byte to the application.

Can anybody confirm this behaviour?

Is there any workaound? - probably to split the payload when detected critical size combination.

#windows7 #usb #cdc #vcp

qwer.asdf · ‎2015-05-27

Posted on May 27, 2015 at 15:57

Maybe for some reason the microcontroller doesn't send the NAK packet to inform that there is no more data coming? What USB library are you using?

Also, according to

, maximum packet size for USB FS is 1023 bytes, are you using USB FS or USB HS?