Re: [libopenstm32-devel] stm32f103 and USB

[Gareth M. <ga...@bl...>]

On Wed, Feb 16, 2011 at 8:38 AM, Gareth McMullin
<ga...@bl...> wrote:
> Ok, there seems to be a lurking bug in the USB code.  You aren't the
> first person to have this problem.  I unfortunately can't reproduce the
> problem with either of the two hosts I have available.

I've found the problem:  just tried building with summon-arm-toolchain,
and I observe the same problem.  The build_config_descriptor() function
uses memcpy() to contruct the configuration descriptor, on entry to memcpy
an invalid instruction is encountered and the target is found in
blocking_handler().
No further USB requests are handled.

It seems that summon-arm-toolchain is linking in an ARM mode memcpy
instead of thumb.  This can be solved by adding -mthumb to the linker
options.

I've attached a patch to the generic makefile, which just added the full CFLAGS
to the linker command line.  It solved the problem and should be safe.
I've also removed the "-Wl,--gc-sections", and changed options to "-O0 -g3".
The options in git make the examples very hard to debug, and I think this
may create a barrier to newbies trying out the library.  Especially
for an example,
we can give up some size to make things easier.

Regards,
Gareth

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