[Info-vax] USB based serial ports, was: Re: Useless Serial Bus

[Simon Clubley]

On 2011-10-29, JF Mezei <jfmezei.spamnot at vaxination.ca> wrote:
>
> I am not privy to all the info on serial interfaces for USB, but some of
> the more popular ones that work come with FTDI drivers for various
> platforms because the standard USB drivers for serial interfaces are
> brain dead.

That should be "brain dead under Windows". All the reports I've seen say
that the Linux USB CDC driver works just fine.

However, since the majority of people wanting to use a USB based serial
port seem to want to do it under Windows, it does mean that the various
vendors have chosen to use the vendor specific USB class and hence a vendor
specific API and drivers.

There are two main vendors in the marketplace at the moment: Prolific with
it's PL-2303 device range which addresses the commodity end of the market
and FTDI with it's range of devices which address the more higher-end part
of the market.

Both vendors have the _very_ annoying requirement that the programming
specs needed to write your own driver are only available if you sign a NDA.

However, I've recently been pleasantly surprised to find that Microchip
are offering the MCP2200 IC for people who wish to build their own serial
adapter hardware and which implements the same basic capabilities as FTDI
but uses the standard USB classes to do it.

(Unfortunately, it's only available in SOIC (and smaller) packaging and I
live in a PDIP sized world. That's especially annoying because the MCP2200
is just a PIC18F with custom firmware and the base PIC device is available
in PDIP packaging. Given the price of the SOIC->DIP adapters which don't
require you to solder the device onto the board, I am seriously considering
just writing my own CDC implementation for the base PIC18F device. It would
make a nice little programming project sometime.)

As you can see, this is a area I have spent some time looking at...

BTW, what's the situation with the USB CDC driver under OS/X ?

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world