                  LibNXT and FwFlash
                        v0.3
                    David Anderson
                 ====================

What?
=====

LibNXT is an utility library for talking to the LEGO Mindstorms NXT
intelligent brick at a relatively low level. It currently does:

 - Handling USB communication and locating the NXT in the USB tree.
 - Interaction with the Atmel AT91SAM boot assistant.
 - Flashing of a firmware image to the NXT.
 - Execution of code directly in RAM.

(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.


Who?
====

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.

When?
=====

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 :-)

How?
====

To compile all of this you'll need a copy of libusb 0.1 on your
system, as well as the scons project manager.

 - Libusb 0.1: http://libusb.sf.net/
 - Scons: http://www.scons.org/

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.
