GRBL学习

grbl.h

#ifndef grbl_h
#define grbl_h

// Grbl versioning system
#define GRBL_VERSION "0.9j"
#define GRBL_VERSION_BUILD "20160726"

// Define standard libraries used by Grbl.
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>
#include <avr/wdt.h>
#include <util/delay.h>
#include <math.h>
#include <inttypes.h>    
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>

// Define the Grbl system include files. NOTE: Do not alter organization.
#include "config.h"
#include "nuts_bolts.h"
#include "settings.h"
#include "system.h"
#include "defaults.h"
#include "cpu_map.h"
#include "coolant_control.h"
#include "eeprom.h"
#include "gcode.h"
#include "limits.h"
#include "motion_control.h"
#include "planner.h"
#include "print.h"
#include "probe.h"
#include "protocol.h"
#include "report.h"
#include "serial.h"
#include "spindle_control.h"
#include "stepper.h"

#endif

grbl.h中所包含各种必备的头文件，以及版本号和ID，在实际应用中，grbl更新的时候，是需要更改版本ID才能正常更新固件的，否则是更新不进去的。

limits.c/.h

从文件名上可以知道，两个文件是和限位相关的。这些地方影响着回零动作。
依旧从头文件开始：

// Initialize the limits module
void limits_init();

// Disables hard limits.
void limits_disable();

// Returns limit state as a bit-wise uint8 variable.
uint8_t limits_get_state();

// Perform one portion of the homing cycle based on the input settings.
void limits_go_home(uint8_t cycle_mask);

// Check for soft limit violations
void limits_soft_check(float *target);

事实上有用的只有这个几个函数：

• 限位初始化
• 限位禁用
• 限位状态获取
• 回零动作
• 软限位检测

没错，这些动作都是可以通过指令来进行配置的或执行的，所以这些就是执行函数的原型。在.c文件上看，其实也很简单的：

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

  #ifdef DISABLE_LIMIT_PIN_PULL_UP
    LIMIT_PORT &= ~(LIMIT_MASK); // Normal low operation. Requires external pull-down.
  #else
    LIMIT_PORT |= (LIMIT_MASK);  // Enable internal pull-up resistors. Normal high operation.
  #endif

  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
}

这里其实就是初始化引脚，配置成输入上拉模式等等，并且使能中断模式。

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

这里的操作是禁用中断模式。

uint8_t limits_get_state()
{
    
    
  uint8_t limit_state = 0;
  uint8_t pin = (LIMIT_PIN & LIMIT_MASK);
  #ifdef INVERT_LIMIT_PIN_MASK
    pin ^= INVERT_LIMIT_PIN_MASK;
  #endif
  if (bit_isfalse(settings.flags,BITFLAG_INVERT_LIMIT_PINS)) {
    
     pin ^= LIMIT_MASK; }
  if (pin) {
    
      
    uint8_t idx;
    for (idx=0; idx<N_AXIS; idx++) {
    
    
      if (pin & get_limit_pin_mask(idx)) {
    
     limit_state |= (1 << idx); }
    }
  }
  return(limit_state);
}

这里获取限位状态，其实就是扫描引脚的电平。

#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 (!(sys_rt_exec_alarm)) {
    
    
        #ifdef HARD_LIMIT_FORCE_STATE_CHECK
          // Check limit pin state. 
          if (limits_get_state()) {
    
    
            mc_reset(); // Initiate system kill.
            bit_true_atomic(sys_rt_exec_alarm, (EXEC_ALARM_HARD_LIMIT|EXEC_CRITICAL_EVENT)); // Indicate hard limit critical event
          }
        #else
          mc_reset(); // Initiate system kill.
          bit_true_atomic(sys_rt_exec_alarm, (EXEC_ALARM_HARD_LIMIT|EXEC_CRITICAL_EVENT)); // Indicate hard limit critical event
        #endif
      }
    }
  }  
#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 (!(sys_rt_exec_alarm)) {
    
    
        // Check limit pin state. 
        if (limits_get_state()) {
    
    
          mc_reset(); // Initiate system kill.
          bit_true_atomic(sys_rt_exec_alarm, (EXEC_ALARM_HARD_LIMIT|EXEC_CRITICAL_EVENT)); // Indicate hard limit critical event
        }
      }  
    }
  }
#endif

这里是对应引脚的中断服务函数。实际就是判断状态来判断是否需要产生警告。