USB CDC Problem 4096 bytes

Discussion created by lpcware Employee on Jun 15, 2016
Content originally posted in LPCWare by mb1391 on Tue Feb 11 01:46:25 MST 2014

I am using nxpUSBlib v0.98b and LPCExpresso v6.1.0 for USB Virtual com port implementation on LPC17xx-40xx.

I have a problem sending data from target hardware to a Windows PC, while PC to target hardware is working fine.

When I send bytes from target hardware to PC, I am supposed to see the data at PC end immediately. But the data gets stuck somewhere and when I keep sending the data, all of a sudden I get 4096 bytes of the stuck data on PC. So I have to wait for data until 4096 bytes are sent.

As far as I know, the usbser.sys requests 4096 bytes at a time by default, but data of lesser size is allowed to be sent over the virtual com port.

What could be the possible issue here?