Re: [Openocd-development] ftd2xx -> libftdi

[Xiaofan C. <xia...@gm...>]

On Fri, Jun 26, 2009 at 11:49 PM, Freddie Chopin<fre...@op...> wrote:
> Ronald Vanschoren pisze:
>> I have only taken a quick look at WinUSB, but if I understand the
>> concept correctly there might be an issue. I'm not sure of what I'm
>> saying here so shout if it's complete nonsense. To work with WinUSB,
>> your USB device has to indicate that WinUsb.sys is its driver. In the
>> case of e.g. a Luminary eval board this can probably be done by making
>> the correct .inf file or whatever (again, I'm not an expert in this).
>> The problem I see is that all other tools using FTD2xx (like the
>> Luminary Flash tool (I suppose)) will no longer be able to connect to
>> the board as it is not "linked" to the FTD2xx driver. Does this make
>> sense? And does this apply to libusb+libftdi as well?
>
> That's perfectly true - you have to use 2 different drivers for software
> based on ftd2xx.dll and WinUSB. That's why that's not so perfect... /;
>


If you use WinUSB or libusb-win32 device driver to replace the original driver
(FTDI driver), the original driver will no longer work. That is a
disadvantage of using
an alternative driver in place of the official driver (especially a
WHQL driver).
Sometimes Windows will refuse to let a driver to load to replace a WHQL driver.

That is why I think to use the FTDI driver and FTD2xx DLL is still the best
for Windows users in terms of ease of use. Still now that the GPL issue
makes this best solution not possible (for binary distribution).

Therefore the 2nd best solution for Windows user may be to get a
GPL-compatible re-implementation of D2XX (or get FTDI to change the license
to GPL-compatible which is more difficult IMHO). You can not based this
DLL on libftdi or libusb because of the underling driver issue.

After that, the solution will be to use WinUSB (or libusb-win32 1.0 if it can
be released within a reasonable time frame).

In this world, there is always difficult to get the best optimum solution.
So we need to get working solutions first and live with the limitations.


-- 
Xiaofan http://mcuee.blogspot.com