Add A axis. Move DIR/STEP pins to PORTA.

Signed-off-by: Alexander Danilov <alexander.a.danilov@gmail.com>

config.h

@@ -28,42 +28,45 @@
 
 // Define pin-assignments
 // NOTE: All step bit and direction pins must be on the same port.
-#define STEPPING_DDR       DDRD
-#define STEPPING_PORT      PORTD
-#define X_STEP_BIT         2  // Uno Digital Pin 2
-#define Y_STEP_BIT         3  // Uno Digital Pin 3
-#define Z_STEP_BIT         4  // Uno Digital Pin 4
-#define X_DIRECTION_BIT    5  // Uno Digital Pin 5
-#define Y_DIRECTION_BIT    6  // Uno Digital Pin 6
-#define Z_DIRECTION_BIT    7  // Uno Digital Pin 7
-#define STEP_MASK ((1<<X_STEP_BIT)|(1<<Y_STEP_BIT)|(1<<Z_STEP_BIT)) // All step bits
-#define DIRECTION_MASK ((1<<X_DIRECTION_BIT)|(1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT)) // All direction bits
+#define STEPPING_DDR       DDRA
+#define STEPPING_PORT      PORTA
+#define X_STEP_BIT         0  // Uno Digital Pin 2
+#define Y_STEP_BIT         1  // Uno Digital Pin 3
+#define Z_STEP_BIT         2  // Uno Digital Pin 4
+#define A_STEP_BIT         3
+#define X_DIRECTION_BIT    4  // Uno Digital Pin 5
+#define Y_DIRECTION_BIT    5  // Uno Digital Pin 6
+#define Z_DIRECTION_BIT    6  // Uno Digital Pin 7
+#define A_DIRECTION_BIT    7
+#define STEP_MASK ((1<<X_STEP_BIT)|(1<<Y_STEP_BIT)|(1<<Z_STEP_BIT)|(1<<A_STEP_BIT)) // All step bits
+#define DIRECTION_MASK ((1<<X_DIRECTION_BIT)|(1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT)|(1<<A_DIRECTION_BIT)) // All direction bits
 #define STEPPING_MASK (STEP_MASK | DIRECTION_MASK) // All stepping-related bits (step/direction)
 
 #define STEPPERS_DISABLE_DDR    DDRB
 #define STEPPERS_DISABLE_PORT   PORTB
-#define STEPPERS_DISABLE_BIT    0  // Uno Digital Pin 8
+#define STEPPERS_DISABLE_BIT    6  // Uno Digital Pin 8
 #define STEPPERS_DISABLE_MASK (1<<STEPPERS_DISABLE_BIT)
 
 // NOTE: All limit bit pins must be on the same port
 #define LIMIT_DDR       DDRB
 #define LIMIT_PIN       PINB
 #define LIMIT_PORT      PORTB
-#define X_LIMIT_BIT     1  // Uno Digital Pin 9
-#define Y_LIMIT_BIT     2  // Uno Digital Pin 10
-#define Z_LIMIT_BIT     3  // Uno Digital Pin 11
+#define X_LIMIT_BIT     0  // Uno Digital Pin 9
+#define Y_LIMIT_BIT     1  // Uno Digital Pin 10
+#define Z_LIMIT_BIT     2  // Uno Digital Pin 11
+#define A_LIMIT_BIT     3
 #define LIMIT_INT       PCIE0  // Pin change interrupt enable pin
-#define LIMIT_INT_vect  PCINT0_vect 
+#define LIMIT_INT_vect  PCINT0_vect
 #define LIMIT_PCMSK     PCMSK0 // Pin change interrupt register
 #define LIMIT_MASK ((1<<X_LIMIT_BIT)|(1<<Y_LIMIT_BIT)|(1<<Z_LIMIT_BIT)) // All limit bits
 
-#define SPINDLE_ENABLE_DDR   DDRB
-#define SPINDLE_ENABLE_PORT  PORTB
-#define SPINDLE_ENABLE_BIT   4  // Uno Digital Pin 12
+#define SPINDLE_ENABLE_DDR   DDRC
+#define SPINDLE_ENABLE_PORT  PORTC
+#define SPINDLE_ENABLE_BIT   5  // Uno Digital Pin 12
 
-#define SPINDLE_DIRECTION_DDR   DDRB
-#define SPINDLE_DIRECTION_PORT  PORTB
-#define SPINDLE_DIRECTION_BIT   5  // Uno Digital Pin 13 (NOTE: D13 can't be pulled-high input due to LED.)
+#define SPINDLE_DIRECTION_DDR   DDRC
+#define SPINDLE_DIRECTION_PORT  PORTC
+#define SPINDLE_DIRECTION_BIT   6  // Uno Digital Pin 13 (NOTE: D13 can't be pulled-high input due to LED.)
 
 #define COOLANT_FLOOD_DDR   DDRC
 #define COOLANT_FLOOD_PORT  PORTC
@@ -76,7 +79,7 @@
   #define COOLANT_MIST_DDR   DDRC
   #define COOLANT_MIST_PORT  PORTC
   #define COOLANT_MIST_BIT   4 // Uno Analog Pin 4
-#endif  
+#endif
 
 // NOTE: All pinouts pins must be on the same port
 #define PINOUT_DDR       DDRC
@@ -97,6 +100,7 @@
 #define DEFAULT_X_STEPS_PER_MM (94.488188976378*MICROSTEPS)
 #define DEFAULT_Y_STEPS_PER_MM (94.488188976378*MICROSTEPS)
 #define DEFAULT_Z_STEPS_PER_MM (94.488188976378*MICROSTEPS)
+#define DEFAULT_A_STEPS_PER_MM (94.488188976378*MICROSTEPS)
 #define DEFAULT_STEP_PULSE_MICROSECONDS 10
 #define DEFAULT_MM_PER_ARC_SEGMENT 0.1
 #define DEFAULT_RAPID_FEEDRATE 500.0 // mm/min
@@ -120,8 +124,8 @@
 
 // Define runtime command special characters. These characters are 'picked-off' directly from the
 // serial read data stream and are not passed to the grbl line execution parser. Select characters
-// that do not and must not exist in the streamed g-code program. ASCII control characters may be 
-// used, if they are available per user setup. Also, extended ASCII codes (>127), which are never in 
+// that do not and must not exist in the streamed g-code program. ASCII control characters may be
+// used, if they are available per user setup. Also, extended ASCII codes (>127), which are never in
 // g-code programs, maybe selected for interface programs.
 // TODO: Solidify these default characters. Temporary for now.
 #define CMD_STATUS_REPORT '?'
@@ -131,10 +135,10 @@
 
 // The temporal resolution of the acceleration management subsystem. Higher number give smoother
 // acceleration but may impact performance.
-// NOTE: Increasing this parameter will help any resolution related issues, especially with machines 
-// requiring very high accelerations and/or very fast feedrates. In general, this will reduce the 
+// NOTE: Increasing this parameter will help any resolution related issues, especially with machines
+// requiring very high accelerations and/or very fast feedrates. In general, this will reduce the
 // error between how the planner plans the motions and how the stepper program actually performs them.
-// However, at some point, the resolution can be high enough, where the errors related to numerical 
+// However, at some point, the resolution can be high enough, where the errors related to numerical
 // round-off can be great enough to cause problems and/or it's too fast for the Arduino. The correct
 // value for this parameter is machine dependent, so it's advised to set this only as high as needed.
 // Approximate successful values can range from 30L to 100L or more.
@@ -153,13 +157,13 @@
 
 // Time delay increments performed during a dwell. The default value is set at 50ms, which provides
 // a maximum time delay of roughly 55 minutes, more than enough for most any application. Increasing
-// this delay will increase the maximum dwell time linearly, but also reduces the responsiveness of 
-// run-time command executions, like status reports, since these are performed between each dwell 
+// this delay will increase the maximum dwell time linearly, but also reduces the responsiveness of
+// run-time command executions, like status reports, since these are performed between each dwell
 // time step. Also, keep in mind that the Arduino delay timer is not very accurate for long delays.
 #define DWELL_TIME_STEP 50 // Integer (1-255) (milliseconds)
 
 // Number of homing cycles performed after when the machine initially jogs to limit switches.
-// This help in preventing overshoot and should improve repeatability. This value should be one or 
+// This help in preventing overshoot and should improve repeatability. This value should be one or
 // greater.
 #define N_HOMING_CYCLE 2 // Integer (1-128)
 
@@ -170,54 +174,54 @@
 #define N_STARTUP_LINE 3 // Integer (1-5)
 
 // ---------------------------------------------------------------------------------------
-// FOR ADVANCED USERS ONLY: 
+// FOR ADVANCED USERS ONLY:
 
 // The number of linear motions in the planner buffer to be planned at any give time. The vast
-// majority of RAM that Grbl uses is based on this buffer size. Only increase if there is extra 
+// majority of RAM that Grbl uses is based on this buffer size. Only increase if there is extra
 // available RAM, like when re-compiling for a Teensy or Sanguino. Or decrease if the Arduino
 // begins to crash due to the lack of available RAM or if the CPU is having trouble keeping
-// up with planning new incoming motions as they are executed. 
+// up with planning new incoming motions as they are executed.
 // #define BLOCK_BUFFER_SIZE 18  // Uncomment to override default in planner.h.
 
-// Line buffer size from the serial input stream to be executed. Also, governs the size of 
+// Line buffer size from the serial input stream to be executed. Also, governs the size of
 // each of the startup blocks, as they are each stored as a string of this size. Make sure
 // to account for the available EEPROM at the defined memory address in settings.h and for
 // the number of desired startup blocks.
-// NOTE: 50 characters is not a problem except for extreme cases, but the line buffer size 
-// can be too small and g-code blocks can get truncated. Officially, the g-code standards 
-// support up to 256 characters. In future versions, this default will be increased, when 
+// NOTE: 50 characters is not a problem except for extreme cases, but the line buffer size
+// can be too small and g-code blocks can get truncated. Officially, the g-code standards
+// support up to 256 characters. In future versions, this default will be increased, when
 // we know how much extra memory space we can re-invest into this.
 // #define LINE_BUFFER_SIZE 50  // Uncomment to override default in protocol.h
-  
+
 // Serial send and receive buffer size. The receive buffer is often used as another streaming
 // buffer to store incoming blocks to be processed by Grbl when its ready. Most streaming
-// interfaces will character count and track each block send to each block response. So, 
+// interfaces will character count and track each block send to each block response. So,
 // increase the receive buffer if a deeper receive buffer is needed for streaming and avaiable
 // memory allows. The send buffer primarily handles messages in Grbl. Only increase if large
 // messages are sent and Grbl begins to stall, waiting to send the rest of the message.
 // #define RX_BUFFER_SIZE 128 // Uncomment to override defaults in serial.h
 // #define TX_BUFFER_SIZE 64
-  
+
 // Toggles XON/XOFF software flow control for serial communications. Not officially supported
 // due to problems involving the Atmega8U2 USB-to-serial chips on current Arduinos. The firmware
-// on these chips do not support XON/XOFF flow control characters and the intermediate buffer 
-// in the chips cause latency and overflow problems with standard terminal programs. However, 
+// on these chips do not support XON/XOFF flow control characters and the intermediate buffer
+// in the chips cause latency and overflow problems with standard terminal programs. However,
 // using specifically-programmed UI's to manage this latency problem has been confirmed to work.
 // As well as, older FTDI FT232RL-based Arduinos(Duemilanove) are known to work with standard
 // terminal programs since their firmware correctly manage these XON/XOFF characters. In any
 // case, please report any successes to grbl administrators!
 // #define ENABLE_XONXOFF // Default disabled. Uncomment to enable.
 
 // Creates a delay between the direction pin setting and corresponding step pulse by creating
-// another interrupt (Timer2 compare) to manage it. The main Grbl interrupt (Timer1 compare) 
-// sets the direction pins, and does not immediately set the stepper pins, as it would in 
-// normal operation. The Timer2 compare fires next to set the stepper pins after the step 
-// pulse delay time, and Timer2 overflow will complete the step pulse, except now delayed 
+// another interrupt (Timer2 compare) to manage it. The main Grbl interrupt (Timer1 compare)
+// sets the direction pins, and does not immediately set the stepper pins, as it would in
+// normal operation. The Timer2 compare fires next to set the stepper pins after the step
+// pulse delay time, and Timer2 overflow will complete the step pulse, except now delayed
 // by the step pulse time plus the step pulse delay. (Thanks langwadt for the idea!)
 //   This is an experimental feature that should only be used if your setup requires a longer
 // delay between direction and step pin settings (some opto coupler based drivers), as it may
-// adversely effect Grbl's high-end performance (>10kHz). Please notify Grbl administrators 
-// of your successes or difficulties, as we will monitor this and possibly integrate this as a 
+// adversely effect Grbl's high-end performance (>10kHz). Please notify Grbl administrators
+// of your successes or difficulties, as we will monitor this and possibly integrate this as a
 // standard feature for future releases. However, we suggest to first try our direction delay
 // hack/solution posted in the Wiki involving inverting the stepper pin mask.
 // NOTE: Uncomment to enable. The recommended delay must be > 3us and the total step pulse