Add digipot i2c control for MCP4451
Allow M907 to set i2c digipot currents in amps
Fix Makefile to allow Azteeg motherboards
Fix Makefile to allow Wire libraries only
Add beeper pin for Azteeg X3 Pro

I added #define for LCD_FEEDBACK_FREQUENCY_HZ and
LCD_FEEDBACK_FREQUENCY_DURATION_MS  which is used to alter the default
buzzer sound.

When selecting Panelolu2 in configuration.h:
- it automatically sets the correct ENCODER_PULSES_PER_STEP and
ENCODER_STEPS_PER_MENU_ITEM.
- if LCD_USE_I2C_BUZZER is defined it will also set the default
LCD_FEEDBACK_FREQUENCY_HZ and LCD_FEEDBACK_FREQUENCY_DURATION_MS

When selecting the sanguinololu 1284p the following is true:
- its now enables  LARGE_FLASH
- It enables the gcode M300 when the panelolu2 LCD_USE_I2C_BUZZER is
defined

For some reason that I can’t figure out, the decimal is dropped when
using ’S’ for the code.

Also some minor code improvements to M200.

This is why I wanted to sleep on the code I wrote while falling asleep
rather than immediately submitting a pull request.

This seems to defeat the purpose of previous_millis_cmd, preventing the
time elapsed from previous_millis_cmd from ever reaching
max_inactive_time or stepper_inactive_time while the heat was on.

Fixes a bug in the Extruder Runout Prevention feature that caused the
extruder to move back to “current_position” after a move if it was
activated while the move was in progress. For long home moves (which
are longer than the dimensions of the machine’s working area), this
would cause the machine to crash into the far end of its travel after
homing. This usually occurred on the Z axis, which could result in
damage to the machine if you don’t hit the reset button in time.

Unable to compile if ENABLE_AUTO_BED_LEVELING is not set (not set by default).

Signed-off-by: Joseivaldo Benito Junior <jrbenito@benito.qsl.br>

Signed-off-by: Joseivaldo Benito Junior <jrbenito@benito.qsl.br>

This reverts commit b7eadb9f37.

if you try to enable Z_DUAL_STEPPER_DRIVERS the error "You cannot have dual drivers for both Y and Z" shows even if you don't have defined Y_DUAL_STEPPER_DRIVERS and don't let you compile the firmware

to solve this problem i change this line:

#ifdef Z_DUAL_STEPPER_DRIVERS && Y_DUAL_STEPPER_DRIVERS

to:

#if defined (Z_DUAL_STEPPER_DRIVERS) && defined (Y_DUAL_STEPPER_DRIVERS)

now the error only show if you define both Z_DUAL_STEPPER_DRIVERS and Y_DUAL_STEPPER_DRIVERS

The code for the LSQ solver (qr_solve) is copyrighted by John Burkardt and released under LGPL here:
http://people.sc.fsu.edu/~%20jburkardt/c_src/qr_solve/qr_solve.html
(see qr_solve.cpp for further copyright information)

Removed the calculation of the inverse matrix since the rotation matrix is orthogonal, therefore inverted == transposed.
Much simpler and mathematically robust.

In some cases the Bed Heater FET heats up more then stepper drivers, so
this change add the bed monitoring to the controller fan. As soon as the
bed heater is turned on, the controller fan will run as well.

Recommended for those who are using the Z Probe for Z Homing (as
Z-Endstop)

This feature has two changes:

1) Allow user to choose where the Z Probe will touch the bed when homing
all axis together (G28) by setting below defines:

Z_SAFE_HOMING_X_POINT
Z_SAFE_HOMING_Y_POINT

2) Prevents the user to perform Z Axis Homing when the Z Probe is
outsite bed.

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.

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.

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