Improving Windows support for AVRDUDE

[Marius Greuel]

I would like to make a few proposals for improving the Windows version of
avrdude.

 

IMHO, the biggest issue with avrdude on Windows is the lack of native driver
support, which is due the dependency on libusb and libftdi. Both
implementations are based on the Windows port libusb-win32, which includes
its own kernel driver libusb0.sys. While libusb-win32 does provide the
functionality, it has its own set of problems. Most importantly, libusb it
is not the way to go on Windows: The proper way to access USB devices is to
either use the vendor stock drivers or system supplies drivers, for instance
the Atmel or FTDI supplies drivers. Windows users of avrdude are well aware
of the required workarounds to get libusb installed, such as using Zadig. It
really becomes a nightmare when you use other applications in parallel,
where one application, such Atmel Studio, requires the vendor drivers and
avrdude requires libusb.

 

Now, for Windows users, it would be nice if avrdude just "works out of the
box", as it does on Linux. One of the key points is to move away from the
libusb0.sys driver to the WinUSB driver. WinUSB is the Windows equivalent of
libusb, which is what people use (including Atmel) when you do not want to
cook up your own USB driver. Some choose to use the HID stack, which works
equally well.

 

As a first step, I hacked up a libusb compatible library for avrdude, that
adds support for both libusb(K) and WinUSB. Having WinUSB support enables
Windows users to move away from libusb, while providing backwards
compatibility. All in all, my patches seem to work for the devices I own,
such as AVRISP MKII, but there are probably issues that need to be fixed.

 

My avrdude repo with the patched libraries in the 'external' folder can be
viewed here:

https://github.com/mariusgreuel/avrdude

 

The second step, which is not really related to avrdude, is to increase
awareness of the problems, and get people to actually support WinUSB for
their devices. The easiest way to get Windows to load the WinUSB driver
automatically, is to add a WinUSB compatibility descriptor to the device
firmware. Alternatively, a signed INF file referencing WinUSB will do. Here
is a demo for USBasp:

https://github.com/mariusgreuel/USBasp

 

The question for me is how we proceed with regards to avrdude. I am curious
on a) whether there is any interest at all, b) what your thoughts on this
are, c) what the requirements would be to get changes accepted. Note that my
repo contains a bunch of other patches, which should not be the scope of
this discussion - the patched libusb library is well isolated from these
patches.

 

If there is sufficient interest, I'd be willing to spend some time cleaning
up the code, make changes, and perhaps move the libusb patches into a
library. I think this can be done in a minimal intrusive way that won't
offend Linux users.

 

Marius