[avrdude-dev] modifications to Bus Pirate module

[Tim Vaughan]

Dear AVRDude dudes,

First off, thanks for writing such an awesome tool - if it weren't for
you, I wouldn't be able to tinker with AVRs.  (What a sad and
miserable life that would be! :-) )

In case you're interested, I've made a couple of changes/improvements
I've made to the support for dangerousprototypes.com's Bus Pirate.

The first change is structural.  During initialization, the previous
buspirate.c (specifically, buspirate_enable() ) sent a reset command
to the BP and parsed the resulting serial output to determine the
versions of the BP hardware and firmware.  This was then used to
determine whether the binary SPI mode could be used for communication
with the MCU.  Unfortunately, this approach has been a source of
ongoing compatibility issues due to small changes made to the BP user
interface over the last few firmware revisions.  Furthermore, the
initial reset command will cause havoc with the next version of the BP
hardware (v4), as it will cause the USB connection to the BP to
disappear and reattach.

Following the suggestion of Ian Lesnet, the lead BP developer, I've
therefore removed the initial reset, as well as any attempt to detect
the BP hardware or firmware versions via the BP user interface.
Instead, I've implemented a try-then-fallback approach that attempts
to enter the binary SPI mode, then falls back to the original ascii
mode in the event that this fails.  Entering binary mode implicitly
causes the BP to reset its internal mode settings, which is why the
explicit reset is unnecessary, but a reset is still performed in the
event that ascii mode is used. This change fixes all of the recent
compatibility issues as all but the earliest firmware versions support
the binary mode.   (The extended option "ascii" can still be used to
force the use of the legacy ascii SPI mode, if desired.  However,
ascii mode is likely to fail on BPs using recent firmware versions due
again to small changes in the ascii user interface.)

The second change is a feature addition.  Ian has added a new bulk SPI
write command to the latest BP firmware version.  The presence of this
new command is determined during initialization (again by trial and
error, this time in buspirate_start_spi_mode_bin() ) and, if found, a
new buspirate_pagedwrite() function is enabled which makes use of this
command which speeds up writes to AVR flash memory by about a factor
of 4.  I've created an additional extended option "nopagedwrite" which
disables detection and use of this function in case it's not wanted,
and added an appropriate entry to the manpage documenting this new
option.

The attached patch includes these changes and is against the current
svn trunk.  If you're happy with the modifications, please let me know
if there's anything I can do to make them appropriate for inclusion in
the avrdude code base.  I've done my best to keep the
changes/additions in line with the existing style, but no-doubt
there's plenty that could be done better.

Thanks again for all the hard work you guys have put in to opening up
AVR programming to *nix users!

Tim

avrdude_buspirate.patch
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