LibNXT and FwFlash
v0.3
David Anderson
====================LibNXT is an utility library for talking to the LEGO Mindstorms NXT intelligent brick at a relatively low level. It currently does:
(If you have ideas of other stuff it should do, please suggest!)
LibNXT is targetted at the platforms that the official Lego Minstorms NXT software overlooks. Specifically, it will work on any POSIX-compliant operating system where libusb 0.1 (http://libusb.sf.net/) is supported.
The design of LibNXT is layered, meaning you can plug into it at any level of complexity or abstraction you desire, from the lowest level USB bulk bit-pushing interface, to an API exposing the SAM-BA commandset, right up to just calling nxt_firmware_flash() and having everything taken care of!
fwflash is the first utility program that uses LibNXT. As its name
hints, its purpose is to take a NXT firmware image file and flash it
to a connected NXT device.
fwexec is another cool utility, originally written by the folks of
the Lejos project (http://lejos.sourceforge.net/). It takes a
specially compiled firmware image, uploads it to the NXT's RAM, and
executes it directly from there. While this firmware will only last
until the brick is powered down, it is a great tool for testing
firmwares during development without wearing down the flash memory.
Uh, that would be me. David Anderson, linux/open source developer and
enthusiast, and fan of embedded stuff in general. As mentionned above,
the fwexec utility was originally written by Lawrie Griffiths, over
at Lejos.
Started the day after receiving the NXT kit, I started by working out the firmware flashing procedure from the specs and a USB dump of the windows software at work. Since then, after obtaining a proof-of-concept application, I've been implementing this library to abstract the horrors of low-level USB chatter into a nice, clean library.
Release 0.3 (22/04/2007) : more than a year later, there are a few
changes, and it can't hurt to push them out in an
actual release. This release includes a more
intelligent build system that handles a missing flash
driver elegantly, and the fwexec utility program.
Unless people have specific itches that need
scratching, or bugs that should be fixed, this will
probably be the final release of libnxt. My personal
itch is scratched, and I've moved on to using libnxt
to write firmware code :-).
Release 0.2 (17/03/2006) : firmware flashing is now done entirely with open source code. The flash driver routine has been replaced with open source code implementing the flashing procedure.
Release 0.1.1 (10/03/2006) : add big-endian host arch support, and make the firmware image reading process a little less linux-centric (use of the posix open/read/close API instead of mmap).
Release 0.1 (10/03/2006) : featuring the FwFlash utility and a LibNXT with just enough API in it to get FwFlash working :-)
To compile all of this you'll need a copy of libusb 0.1 on your system, as well as the scons project manager.
When you have all that, just run 'scons' in the libnxt directory, and compilation should follow. Once you're done, you can try fwflash out by resetting your NXT (see your user manual for details on this) and running:
./fwflash nxtos.bin
nxtos.bin is the official Lego Mindstorms NXT firmware. You can find this on your current installation of the Mindstorms software, or on LEGO's website.
If all goes well, fwflash should inform you that it has found the NXT on your USB device bus, and that flashing has started. After a few seconds, it should announce successful flashing, and say that it has booted the new firmware, which should be answered by the greeting sound of the LEGO firmware as the brick starts up :-).
If it doesn't, well it's either a problem with your USB device permissions (if fwflash can't find the NXT), or it's a bug (if the brick doesn't reboot properly, or if some weird error is reported by fwflash and it bombs out.
The release tarball comes with a 'flash.bin'. This file is the compiled version of the embedded flash driver, which is uploaded to the NXT's RAM and required to write data into flash memory.
If you do not have a release tarball, or accidentally deleted your copy of flash.bin, there are several options. If you have an ARM7 cross-compiler toolchain, you can simply type 'make' in the 'flash_write' subdirectory to rebuild the flash driver.
If you don't have a suitable cross-compiler, you can just run 'scons' as usual. The build system will see that the flash driver is missing, and offer to download a binary copy from the LibNXT website and use that.