> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu] On Behalf Of Tomas Larsson
> Sent: Friday, February 10, 2006 9:38 AM
> To: 'Microcontroller discussion list - Public.'
> Subject: RE: [PIC]: Getting started with USB
> 
> 
> > -----Original Message-----
> > From: piclist-bounces@mit.edu
> > [mailto:piclist-bounces@mit.edu] On Behalf Of Robert Young
> > Sent: Friday, February 10, 2006 4:03 PM
> > To: 'Microcontroller discussion list - Public.'
> > Subject: RE: [PIC]: Getting started with USB
> > 
> > 
> > 
> > > -----Original Message-----
> > > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On 
> > > Behalf Of Alan B. Pearce
> > > Sent: Friday, February 10, 2006 8:39 AM
> > > To: Microcontroller discussion list - Public.
> > > Subject: Re: [PIC]: Getting started with USB
> > > 
> > > 
> > > >The FDTI chip normaly emulates a comport,
> > > 
> > > While I agree this is true for the FT232 serial chips, I 
> am not sure 
> > > about the FT245. I was assuming it looked like a parallel printer 
> > > port to the OS.
> > 
> > No.  There are two drivers available from FTDI, the VCP 
> (Virtual Comm
> > Port) and D2XX native mode drivers.
> > 
> > All FTDI chips when used with the VCP drivers look like a
> > serial port to the PC.  It is also possible to make the 
> > device look like a serial port using the D2XX drivers too but 
> > not nearly as simple.
> 
> Yeah, but the most common application seems to be USB-RS232, 
> and to emulate a com-port. For those that don't have a comport.
> 
> 
> One thing though, this type of emulation drives me nuts, I 
> have a number of commercial stuff based on the fdti-chip, 
> emulating com-ports, and it seems to change com-port each 
> time it's used, its very frustrating.
> 

There are a couple of things that could be happening.  First, if you own
more than one FTDI USB-RS232 dongle and they have been programmed with
unique serial numbers, they will appear as different COM ports if you
swap dongles.

I have also seen the COM port shuffle problem with a single device if it
is repeatedly installed and uninstalled.  Somehow not everything is
removed from the registry and eventually Windows thinks it is a unique
device everytime it is plugged in.

Not a complete fix but you should get the latest drivers from
www.ftdichip.com.  Before you do this, they have a utility somewhere on
their site that can work it way through the registry and remove all
references to FTDI devices with VID=0x0403.  

Rob
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist