In previous version, even with PWM = 127, the system turns the FET off
and then on in the next cycle. This bevavior may increase the FET heat
dissipation.
It was fixed keeping the FET always On when PWM=127.

This allows a hot end with two heaters and a FET for each heater. This is useful if the FET is not capable of heating two heaters.

Implement M226 - GCode Initiated Pause

M80 - ATX Power On related modification

Added support for BT on AT90USB devices, corrected LCD bug, added new board and LCD

Fix servo control for Melzi v2.0

Add UUID support to M115 responses.

Add (correct) missing pin definitions for Y2

Implemented M226 as described here:
http://reprap.org/wiki/G-code#M226:_Gcode_Initiated_Pause

Waits for pin to be become either HIGH, LOW or the inverse of what it
was before. Allows printing to pause until user interaction

start another print with suicide feature after a print without
suicide...

Added AT90USB device BT connectivity support using second UART.

I tested this and it works.

If only an LCD is defined and no menu or keyboard defined, there is a
compilation error.

Added conditional compilation.

Made instructions more clear.

Not sure what happened to my last commit so this includes that one + reordering the steps.

Included support for BT dongle on AT90USB boards.
Added LCD Shift Register LCD control
Included support for RepRap Clone Wars project board (SAV MKI).

PS_ON configurable boot state

Allows the user to select wheter or not the PSU should be turned on or
kept in standby when marlin boots

Make G11 not horribly broken

since it can occure in comments.

If a print is stopped, it would be nice in the future to write a file with the printer state, the filename of the print, and the position within the print.
this file could be read, to continue a previously stopped print.
not finished yet.

by overloading M32 it is now possible to execute gcode files from other gcode files, with a fixed recursion level.
This can be used e.g. for having a real start.g and end.g somewhere on the sd card, which are then called from the normal print file.
Another usecase would be to have macro-files for nozzle-change and layerchange.
I have not tested the speedwise performance. The testing was done with pronterface.

syntax:
normal call from sd card will open the new file and continue executing there.
M32 !/path/filename#
this however will call the new file and return to the caller file.
M32 P !/path/filename#
with the optional "S<position>" the  file starting position can be set.
this is for continuing prints from a previous location.

if a '#' is read now the buffer will be emptied before reading ahead.
This is so one can execute files from within gcode files, without messing the buffer with preread characters from the caller file.
# can not occure in sd files imho, because it should only occure within checksums in ther serial communication.
Yes, thats a lame argument. If you have a better idea please tell me. It has to be a character that one can type
on a keyboard manually.

Hopefully fixed viky button handling without braking other boards

This reverts commit 314fd13c.

Added BlinkM support over i2c

- Added "Z_RAISE_BEFORE_HOMING" for raising Z the defined distance
before homing. This is useful to avoid Z-Probe collision when hotend is
near bed.

- Fixed the issue of Z not going bellow Z_PROBE_OFFSET when
"min_software_endstops" is true.
Now the Z_PROBE_OFFSET is not set in Z_MIN_POS, it is added after
homing.

If "SHOW_TEMP_ADC_VALUES" is defined in Configuration_adv.h, the M105
command will present, after tradicional temperatures, the ADC value read
from temp sensors. This is great for adjusting thermistor tables with
thermocouple.

From Pronterface you can see the ADC value and compare with a
thermocouple reading.. then you just need to create your own thermistor
table.

Since this merge doesnt change the original information, it doesnt mess
with PC software parsing (tested under Pronterface and Repetier-Host).

This is _not_ automatically the cronological, since deleting a file will free
the filesystem descriptor for it, which then will be used by the next file copied on it.
Since this makes the auto0.g file very inaccessible, I put the option back, to have it in the prepare menu.

this should satisfy https://github.com/ErikZalm/Marlin/pull/373

as a reminder, auto0.g will be executed every time after a boot with sd card present and file present.
thereafter, if there is a file auto1.g this will be done. Thats IMHO the best place to put settings, and prepare heating.
I also execute again after each (now again via the prepare menu) before starting a new print/ after a failed one.
It for me 100% replaces any start.gcode form the slicers.