limits.c

/*
  limits.c - code pertaining to limit-switches and performing the homing cycle
  Part of Grbl v0.9

  Copyright (c) 2012-2014 Sungeun K. Jeon

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/
/* 
  This file is based on work from Grbl v0.8, distributed under the 
  terms of the MIT-license. See COPYING for more details.  
    Copyright (c) 2009-2011 Simen Svale Skogsrud
    Copyright (c) 2012 Sungeun K. Jeon
*/  
  
#include "system.h"
#include "settings.h"
#include "protocol.h"
#include "planner.h"
#include "stepper.h"
#include "motion_control.h"
#include "limits.h"
#include "report.h"

// Homing axis search distance multiplier. Computed by this value times the axis max travel.
#define HOMING_AXIS_SEARCH_SCALAR  1.5 // Must be > 1 to ensure limit switch will be engaged.


void limits_init() 
{
  LIMIT_DDR &= ~(LIMIT_MASK); // Set as input pins

  if (bit_istrue(settings.flags,BITFLAG_INVERT_LIMIT_PINS)) {
    LIMIT_PORT &= ~(LIMIT_MASK); // Normal low operation. Requires external pull-down.
  } else {
    LIMIT_PORT |= (LIMIT_MASK);  // Enable internal pull-up resistors. Normal high operation.
  }

  if (bit_istrue(settings.flags,BITFLAG_HARD_LIMIT_ENABLE)) {
    LIMIT_PCMSK |= LIMIT_MASK; // Enable specific pins of the Pin Change Interrupt
    PCICR |= (1 << LIMIT_INT); // Enable Pin Change Interrupt
  } else {
    limits_disable(); 
  }
  
  #ifdef ENABLE_SOFTWARE_DEBOUNCE
    MCUSR &= ~(1<<WDRF);
    WDTCSR |= (1<<WDCE) | (1<<WDE);
    WDTCSR = (1<<WDP0); // Set time-out at ~32msec.
  #endif
}


void limits_disable()
{
  LIMIT_PCMSK &= ~LIMIT_MASK;  // Disable specific pins of the Pin Change Interrupt
  PCICR &= ~(1 << LIMIT_INT);  // Disable Pin Change Interrupt
}


// This is the Limit Pin Change Interrupt, which handles the hard limit feature. A bouncing 
// limit switch can cause a lot of problems, like false readings and multiple interrupt calls.
// If a switch is triggered at all, something bad has happened and treat it as such, regardless
// if a limit switch is being disengaged. It's impossible to reliably tell the state of a 
// bouncing pin without a debouncing method. A simple software debouncing feature may be enabled 
// through the config.h file, where an extra timer delays the limit pin read by several milli-
// seconds to help with, not fix, bouncing switches.
// NOTE: Do not attach an e-stop to the limit pins, because this interrupt is disabled during
// homing cycles and will not respond correctly. Upon user request or need, there may be a
// special pinout for an e-stop, but it is generally recommended to just directly connect
// your e-stop switch to the Arduino reset pin, since it is the most correct way to do this.
#ifndef ENABLE_SOFTWARE_DEBOUNCE
  ISR(LIMIT_INT_vect) // DEFAULT: Limit pin change interrupt process. 
  {
    // Ignore limit switches if already in an alarm state or in-process of executing an alarm.
    // When in the alarm state, Grbl should have been reset or will force a reset, so any pending 
    // moves in the planner and serial buffers are all cleared and newly sent blocks will be 
    // locked out until a homing cycle or a kill lock command. Allows the user to disable the hard
    // limit setting if their limits are constantly triggering after a reset and move their axes.
    if (sys.state != STATE_ALARM) { 
      if (bit_isfalse(sys.execute,EXEC_ALARM)) {
        mc_reset(); // Initiate system kill.
        bit_true_atomic(sys.execute, (EXEC_ALARM | EXEC_CRIT_EVENT)); // Indicate hard limit critical event
      }
    }
  }  
#else // OPTIONAL: Software debounce limit pin routine.
  // Upon limit pin change, enable watchdog timer to create a short delay. 
  ISR(LIMIT_INT_vect) { if (!(WDTCSR & (1<<WDIE))) { WDTCSR |= (1<<WDIE); } }
  ISR(WDT_vect) // Watchdog timer ISR
  {
    WDTCSR &= ~(1<<WDIE); // Disable watchdog timer. 
    if (sys.state != STATE_ALARM) {  // Ignore if already in alarm state. 
      if (bit_isfalse(sys.execute,EXEC_ALARM)) {
        uint8_t bits = LIMIT_PIN;
        // Check limit pin state. 
        if (bit_istrue(settings.flags,BITFLAG_INVERT_LIMIT_PINS)) { bits ^= LIMIT_MASK; }
        if (bits & LIMIT_MASK) {
          mc_reset(); // Initiate system kill.
          bit_true_atomic(sys.execute, (EXEC_ALARM | EXEC_CRIT_EVENT)); // Indicate hard limit critical event
        }
      }  
    }
  }
#endif


// Homes the specified cycle axes, sets the machine position, and performs a pull-off motion after
// completing. Homing is a special motion case, which involves rapid uncontrolled stops to locate
// the trigger point of the limit switches. The rapid stops are handled by a system level axis lock 
// mask, which prevents the stepper algorithm from executing step pulses. Homing motions typically 
// circumvent the processes for executing motions in normal operation.
// NOTE: Only the abort runtime command can interrupt this process.
void limits_go_home(uint8_t cycle_mask) 
{
  if (sys.abort) { return; } // Block if system reset has been issued.

  // Initialize homing in search mode to quickly engage the specified cycle_mask limit switches.
  bool approach = true;
  float homing_rate = settings.homing_seek_rate;
  uint8_t invert_pin, idx;
  uint8_t n_cycle = (2*N_HOMING_LOCATE_CYCLE+1);
  float target[N_AXIS];
  
  uint8_t limit_pin[N_AXIS], step_pin[N_AXIS];
  float max_travel = 0.0;
  for (idx=0; idx<N_AXIS; idx++) {  
    // Initialize limit and step pin masks
    limit_pin[idx] = get_limit_pin_mask(idx);
    step_pin[idx] = get_step_pin_mask(idx);

    // Determine travel distance to the furthest homing switch based on user max travel settings.
    // NOTE: settings.max_travel[] is stored as a negative value.
    if (max_travel > settings.max_travel[idx]) { max_travel = settings.max_travel[idx]; }
  }
  max_travel *= -HOMING_AXIS_SEARCH_SCALAR; // Ensure homing switches engaged by over-estimating max travel.
  
  plan_reset(); // Reset planner buffer to zero planner current position and to clear previous motions.
  
  do {
    // Initialize invert_pin boolean based on approach and invert pin user setting.
    if (bit_isfalse(settings.flags,BITFLAG_INVERT_LIMIT_PINS)) { invert_pin = approach; }
    else { invert_pin = !approach; }

    // Initialize and declare variables needed for homing routine.
    uint8_t n_active_axis = 0;
    uint8_t axislock = 0;
        
    for (idx=0; idx<N_AXIS; idx++) {
      // Set target location for active axes and setup computation for homing rate.
      if (bit_istrue(cycle_mask,bit(idx))) { 
        n_active_axis++;
        if (!approach) { target[idx] = -max_travel; }
        else { target[idx] = max_travel; }
      } else {
        target[idx] = 0.0;
      }

      // Set target direction based on cycle mask
      if (bit_istrue(settings.homing_dir_mask,bit(idx))) { target[idx] = -target[idx]; }
      
      // Apply axislock to the step port pins active in this cycle.
      if (bit_istrue(cycle_mask,bit(idx))) { axislock |= step_pin[idx]; }
    }      
    homing_rate *= sqrt(n_active_axis); // [sqrt(N_AXIS)] Adjust so individual axes all move at homing rate.
    sys.homing_axis_lock = axislock;
  
    // Perform homing cycle. Planner buffer should be empty, as required to initiate the homing cycle.
    uint8_t limit_state;
    
    #ifdef USE_LINE_NUMBERS
      plan_buffer_line(target, homing_rate, false, HOMING_CYCLE_LINE_NUMBER); // Bypass mc_line(). Directly plan homing motion.
    #else
      plan_buffer_line(target, homing_rate, false); // Bypass mc_line(). Directly plan homing motion.
    #endif
    
    st_prep_buffer(); // Prep and fill segment buffer from newly planned block.
    st_wake_up(); // Initiate motion
    do {
      // Check limit state. Lock out cycle axes when they change.
      limit_state = LIMIT_PIN;
      if (invert_pin) { limit_state ^= LIMIT_MASK; }
      for (idx=0; idx<N_AXIS; idx++) {
        if (axislock & step_pin[idx]) {
          if (limit_state & limit_pin[idx]) { axislock &= ~(step_pin[idx]); }
        }
      }
      sys.homing_axis_lock = axislock;
      st_prep_buffer(); // Check and prep segment buffer. NOTE: Should take no longer than 200us.
      // Check only for user reset. No time to run protocol_execute_runtime() in this loop.
      if (sys.execute & EXEC_RESET) { protocol_execute_runtime(); return; }
    } while (STEP_MASK & axislock);
    
    st_reset(); // Immediately force kill steppers and reset step segment buffer.
    plan_reset(); // Reset planner buffer. Zero planner positions. Ensure homing motion is cleared.

    delay_ms(settings.homing_debounce_delay); // Delay to allow transient dynamics to dissipate.

    // Reverse direction and reset homing rate for locate cycle(s).
    homing_rate = settings.homing_feed_rate;
    approach = !approach;
    
  } while (n_cycle-- > 0);
    
  // The active cycle axes should now be homed and machine limits have been located. By 
  // default, grbl defines machine space as all negative, as do most CNCs. Since limit switches
  // can be on either side of an axes, check and set axes machine zero appropriately. Also,
  // set up pull-off maneuver from axes limit switches that have been homed. This provides
  // some initial clearance off the switches and should also help prevent them from falsely
  // triggering when hard limits are enabled or when more than one axes shares a limit pin.
  for (idx=0; idx<N_AXIS; idx++) {
    // Set up pull off targets and machine positions for limit switches homed in the negative
    // direction, rather than the traditional positive. Leave non-homed positions as zero and
    // do not move them.
    // NOTE: settings.max_travel[] is stored as a negative value.
    if (cycle_mask & bit(idx)) {
    
      #ifdef HOMING_FORCE_SET_ORIGIN
        sys.position[idx] = 0;  // Set axis homed location as axis origin
        target[idx] = settings.homing_pulloff;  
        if ( bit_isfalse(settings.homing_dir_mask,bit(idx)) ) { target[idx] = -target[idx]; }     
      #else
        if ( bit_istrue(settings.homing_dir_mask,bit(idx)) ) {
          target[idx] = settings.homing_pulloff+settings.max_travel[idx];
          sys.position[idx] = lround(settings.max_travel[idx]*settings.steps_per_mm[idx]);
        } else {
          target[idx] = -settings.homing_pulloff;
          sys.position[idx] = 0;
        }
      #endif
      
    } else { // Non-active cycle axis. Set target to not move during pull-off. 
      target[idx] = (float)sys.position[idx]/settings.steps_per_mm[idx];
    }
  }
  plan_sync_position(); // Sync planner position to current machine position for pull-off move.
  
  #ifdef USE_LINE_NUMBERS
    plan_buffer_line(target, settings.homing_seek_rate, false, HOMING_CYCLE_LINE_NUMBER); // Bypass mc_line(). Directly plan motion.
  #else
    plan_buffer_line(target, settings.homing_seek_rate, false); // Bypass mc_line(). Directly plan motion.
  #endif
  
  // Initiate pull-off using main motion control routines. 
  // TODO : Clean up state routines so that this motion still shows homing state.
  sys.state = STATE_QUEUED;
  bit_true_atomic(sys.execute, EXEC_CYCLE_START);
  protocol_execute_runtime();
  protocol_buffer_synchronize(); // Complete pull-off motion.
  
  // Set system state to homing before returning. 
  sys.state = STATE_HOMING; 
}


// Performs a soft limit check. Called from mc_line() only. Assumes the machine has been homed,
// the workspace volume is in all negative space, and the system is in normal operation.
void limits_soft_check(float *target)
{
  uint8_t idx;
  uint8_t soft_limit_error = false;
  for (idx=0; idx<N_AXIS; idx++) {
   
    #ifdef HOMING_FORCE_SET_ORIGIN
      // When homing forced set origin is enabled, soft limits checks need to account for directionality.
      // NOTE: max_travel is stored as negative
      if (bit_istrue(settings.homing_dir_mask,bit(idx))) {
        if (target[idx] < 0 || target[idx] > -settings.max_travel[idx]) { soft_limit_error = true; }
      } else {
        if (target[idx] > 0 || target[idx] < settings.max_travel[idx]) { soft_limit_error = true; }
      }
    #else  
      // NOTE: max_travel is stored as negative
      if (target[idx] > 0 || target[idx] < settings.max_travel[idx]) { soft_limit_error = true; }
    #endif
    
    if (soft_limit_error) {
      // Force feed hold if cycle is active. All buffered blocks are guaranteed to be within 
      // workspace volume so just come to a controlled stop so position is not lost. When complete
      // enter alarm mode.
      if (sys.state == STATE_CYCLE) {
        bit_true_atomic(sys.execute, EXEC_FEED_HOLD);
        do {
          protocol_execute_runtime();
          if (sys.abort) { return; }
        } while ( sys.state != STATE_IDLE || sys.state != STATE_QUEUED);
      }
    
      mc_reset(); // Issue system reset and ensure spindle and coolant are shutdown.
      bit_true_atomic(sys.execute, (EXEC_ALARM | EXEC_CRIT_EVENT)); // Indicate soft limit critical event
      protocol_execute_runtime(); // Execute to enter critical event loop and system abort
      return;
    }
  }
}