I have problems in USB application...i develope digital boards with microcontollers (ATMEL- AT91..ARM family)...i need USB comunication between board an Personal Computer ..ATMEL gave me a CDC driver ...so i see the USB port as a virtual COM.
I try to explain my problem:
I have done a C code application in PC ( C code written by the support of National Instruments CVI system..do you know? ) comunication routine are the same that i use for serial comunication (built in subroutine for port com) .
I have performed an handshake comunication in which PC is the master: sends 1 message and waits reply from micro before to send new messages
C code application first finds the adapter com number and after sends data to the micro ....
I have checked the application for USB 1.0 USB 2.0 Win200, Win XP...ok but the problem is that the application doesn't work correctly if i use a laptop Computer.
I have put the same application in many PCs..if i try to connect the board, enumeration goes well , comunication no if i use a laptop (in debug i see that micro remains stuck in "Wait for the end of transfer" ..statements 293..296 subroutine cdc_enumerate.c).

I say that enumeratio is OK because the OS in PC recognizes the device as ATMEL AT 91 USB SERIAL EMULATION (in control panel...hardware resources).

Is possible that the virtual com doesn't work in laptop Computer ?

Hi,

in several cases i have experienced similar problems, it seems that the USB drivers for the virtual COM don't work if there are other virtual COM ports in the system. On laptops there are usually IRDA or Bluetooth based virtual COM's.

You could try and disable IRDA (usually virtual COM2) and Bluetooth if you have that (may be nescessary to do in BIOS) - then try again ...


hope this helps !


Regards
Paul