Requires a very recent toolchain, because ATmega32U2 is relatively new.

- Building:

  make

- Uploading the firmware to a Ben (for flashing with the atusb-pgm cable):

  make HOST=<hostname> upload

  Example:

  make HOST=ben upload

  HOST defaults to "jlime".

- Flashing the boot loader:

  Prerequisite: avrdude on the Ben.

  Disconnect the atusb board from USB. Insert the atusb-pgm connector into
  the Ben. Place the atusb-pgm adapter on the exposed contact pads of the
  atusb board and push it down. Then run

  make prog

  This takes about 30 seconds. If the programming fails with an error
  message like "Yikes!  Invalid device signature.", verify that the
  atusb-pgm board is properly connected and placed, then try again.

- Uploading the application:

  Prerequisite: dfu-util installed on the PC.

  Insert atusb into the PC, then run

  make dfu

  Note: since the boot loader resets the USB bus after timing out,
  this operation can fail with a message like "No DFU capable USB device
  found". Just retry, and it will eventually get through.

--------------------------

Making the toolchain:

# patches according to
# http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&p=789527

# some gcc prerequisites

apt-get remove avr-libc gcc-avr binutils-avr
apt-get install libmpfr-dev libmpc-dev

# binutils

wget http://ftp.gnu.org/gnu/binutils/binutils-2.21.tar.bz2
tar xfj binutils-2.21.tar.bz2 
cd binutils-2.21
./configure --target=avr --disable-nls
make
make install

# gcc

wget http://ftpmirror.gnu.org/gcc/gcc-4.5.2/gcc-4.5.2.tar.bz2
wget -O gcc_452_avr.patch http://gcc.gnu.org/bugzilla/attachment.cgi?id=23050
tar xfj gcc-4.5.2.tar.bz2
cd gcc-4.5.2
patch -p1 -s <../gcc_452_avr.patch
mkdir obj-avr
cd obj-avr
../configure --target=avr --enable-languages=c \
    --disable-nls --disable-libssp --with-dwarf2
make
make install

wget http://download.savannah.gnu.org/releases/avr-libc/avr-libc-1.7.1.tar.bz2
tar xfj avr-libc-1.7.1.tar.bz2 
cd avr-libc-1.7.1
./bootstrap	# the automake at the end takes a while
./configure --build=`./config.guess` --host=avr
make
make install
