Okay, so I recently purchased an Arduino Mega and have been playing around with some decent sized unipolar steppers that I salvaged from old 5 1/4" floppy drives. My intention is to someday build a CNC run off the Arduino. It seems that the GRBL project would be the best way to go about controlling the steppers, apart from one small problem: GRBL only sends out pulse and direction signals intended for bipolar motors. I realize that there are hardware drivers out there that can solve this and I could always just use a few binary counters to convert the signals to unipolar steps, however it just seems wrong to use (Buy) extra hardware just to solve a seemingly simple software limitation. (After all, my Mega has plenty of GPIO pins and memory available, unlike the Uno, which GRBL was designed for). Although I am willing to put in some effort to change the relevant source code to make GRBL unipolar-compatable, my knowledge of it's inner workings and C code in general are still very limited, so it would take me a great deal of time.
So, my question is: Has anyone already successfuly modified the GRBL source to include unipolar stepping capabilities? If not, maybe someone with more experience than I could at least point me in the right direction as to where I should start modifying GRBL? From a quick glance at the source on GitHub, I noticed a "stepper.c" file. I'm wondering if all the code relevant to my problem could be found there? When I briefly read through the file, I didn't understand the majority of it and could definitely use some guidance there. Any suggestions would be greatly appreciated!
a unipolar motor can be used as bipolar so that is easy.
in a motordriver is a currentlimiterr.
it means you can step a lot faster
so i would advise drivers as you will always need some sort of amplifier, simple fets are working but current will heat the motor excessive.
Hey guys, thanks for the suggestions. I decided to go with writing my own code for now, just to keep it simple. As for the driver boards, I just ordered some uln2003 Darlingtons (like 20 cents apiece) to amplify the Arduino signals to 12 volts to power the steppers.
You have added your post to a very old Thread.
I'm not sure if you are looking for assistance, but if you are please just try a 30 second youTube clip.
And, of course, explain what assistance you need.
I know, I know .... I mutilated the program ... but works !!!
You can firmware with GRBL_PD2_PC0.bat file, you need only insert the port number like "COM3"
Compare with original and see the differnces!
config.h
/*
config.h - compile time configuration
Part of Grbl
#ifndef config_h
#define config_h
// IMPORTANT: Any changes here requires a full re-compiling of the source code to propagate them.
// Default settings. Used when resetting EEPROM. Change to desired name in defaults.h
#define DEFAULTS_GENERIC
// Serial baud rate
#define BAUD_RATE 9600
// Define pin-assignments
// NOTE: All step bit and direction pins must be on the same port.
#define STEPPING_DDR DDRB
#define STEPPING_PORT PORTB
#define X_STEP_BIT 0 // Uno Digital Pin 2
#define Y_STEP_BIT 0 // Uno Digital Pin 3
#define Z_STEP_BIT 0//4 // Uno Digital Pin 4
#define X_DIRECTION_BIT 6//5 // Uno Digital Pin 5
#define Y_DIRECTION_BIT 7//6 // Uno Digital Pin 6
#define Z_DIRECTION_BIT 0//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_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 5//0 // 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//1 // Uno Digital Pin 9
#define Y_LIMIT_BIT 1//2 // Uno Digital Pin 10
#define Z_LIMIT_BIT 1//3 // Uno Digital Pin 11
#define LIMIT_INT PCIE0 // Pin change interrupt enable pin
#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 0//4 // Uno Digital Pin 12
#define SPINDLE_DIRECTION_DDR DDRB
#define SPINDLE_DIRECTION_PORT PORTB
#define SPINDLE_DIRECTION_BIT 0 // Uno Digital Pin 13 (NOTE: D13 can't be pulled-high input due to LED.)
#define COOLANT_FLOOD_DDR DDRB
#define COOLANT_FLOOD_PORT PORTB
#define COOLANT_FLOOD_BIT 0 // Uno Analog Pin 3
// NOTE: Uno analog pins 4 and 5 are reserved for an i2c interface, and may be installed at
// a later date if flash and memory space allows.
// #define ENABLE_M7 // Mist coolant disabled by default. Uncomment to enable.
#ifdef ENABLE_M7
#define COOLANT_MIST_DDR DDRB
#define COOLANT_MIST_PORT PORTB
#define COOLANT_MIST_BIT 0 // Uno Analog Pin 4
#endif
// NOTE: All pinouts pins must be on the same port
#define PINOUT_DDR DDRB
#define PINOUT_PIN PINB
#define PINOUT_PORT PORTB
#define PIN_RESET 1 // Uno Analog Pin 0
#define PIN_FEED_HOLD 1 // Uno Analog Pin 1
#define PIN_CYCLE_START 1 // Uno Analog Pin 2
#define PINOUT_INT PCIE1 // Pin change interrupt enable pin
#define PINOUT_INT_vect PCINT1_vect
#define PINOUT_PCMSK PCMSK1 // Pin change interrupt register
#define PINOUT_MASK ((1<<PIN_RESET)|(1<<PIN_FEED_HOLD)|(1<<PIN_CYCLE_START))
line 177 from stepper.cpp
/*
stepper.c - stepper motor driver: executes motion plans using stepper motors
Part of Grbl
Copyright (c) 2009-2011 Simen Svale Skogsrud
Copyright (c) 2011-2012 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/>.
*/
/* The timer calculations of this module informed by the 'RepRap cartesian firmware' by Zack Smith
and Philipp Tiefenbacher. */
#include <avr/interrupt.h>
#include "stepper.h"
#include "config.h"
#include "settings.h"
#include "planner.h"
int costyx=1;
int costyy=1;
if (sys.state == STATE_CYCLE) {
// During feed hold, do not update rate and trap counter. Keep decelerating.
st.trapezoid_adjusted_rate = current_block->initial_rate;
set_step_events_per_minute(st.trapezoid_adjusted_rate); // Initialize cycles_per_step_event
st.trapezoid_tick_cycle_counter = CYCLES_PER_ACCELERATION_TICK/2; // Start halfway for midpoint rule.
}
st.min_safe_rate = current_block->rate_delta + (current_block->rate_delta >> 1); // 1.5 x rate_delta
st.counter_x = -(current_block->step_event_count >> 1);
st.counter_y = st.counter_x;
st.counter_z = st.counter_x;
st.event_count = current_block->step_event_count;
st.step_events_completed = 0;
} else {
st_go_idle();
bit_true(sys.execute,EXEC_CYCLE_STOP); // Flag main program for cycle end
}
}
if (current_block != NULL) {
// Execute step displacement profile by bresenham line algorithm
out_bits = current_block->direction_bits;
st.counter_x += current_block->steps_x;
if (st.counter_x > 0) {
out_bits |= (1<<X_STEP_BIT);
st.counter_x -= st.event_count;
if (out_bits & (1<<X_DIRECTION_BIT) ) { sys.position[X_AXIS]--;
//
//UDR0=65;
//DDRD=255;
costyx=costyx-1;
if (costyx < 1) costyx=8;
if (costyx==1) PORTD=0B100000;
if (costyx==2) PORTD=0B110000;
if (costyx==3) PORTD=0B010000;
if (costyx==4) PORTD=0B011000;
if (costyx==5) PORTD=0B001000;
if (costyx==6) PORTD=0B001100;
if (costyx==7) PORTD=0B000100;
if (costyx==8) PORTD=0B100100;
}
else { sys.position[X_AXIS]++;
// UDR0=66;
//DDRD=255;
costyx=costyx+1;
if (costyx > 8) costyx=1;
if (costyx==1) PORTD=0B100000;
if (costyx==2) PORTD=0B110000;
if (costyx==3) PORTD=0B010000;
if (costyx==4) PORTD=0B011000;
if (costyx==5) PORTD=0B001000;
if (costyx==6) PORTD=0B001100;
if (costyx==7) PORTD=0B000100;
if (costyx==8) PORTD=0B100100;
}
}
st.counter_y += current_block->steps_y;
if (st.counter_y > 0) {
out_bits |= (1<<Y_STEP_BIT);
st.counter_y -= st.event_count;
if (out_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--;
//DDRB=255;
costyy=costyy-1;
if (costyy < 1) costyy=8;
if (costyy==1) PORTC=0B1000;
if (costyy==2) PORTC=0B1100;
if (costyy==3) PORTC=0B0100;
if (costyy==4) PORTC=0B0110;
if (costyy==5) PORTC=0B0010;
if (costyy==6) PORTC=0B0011;
if (costyy==7) PORTC=0B0001;
if (costyy==8) PORTC=0B1001;
}
else { sys.position[Y_AXIS]++;
//DDRB=255;
costyy=costyy+1;
if (costyy > 8) costyy=1;
if (costyy==1) PORTC=0B1000;
if (costyy==2) PORTC=0B1100;
if (costyy==3) PORTC=0B0100;
if (costyy==4) PORTC=0B0110;
if (costyy==5) PORTC=0B0010;
if (costyy==6) PORTC=0B0011;
if (costyy==7) PORTC=0B0001;
if (costyy==8) PORTC=0B1001;
}
}
st.counter_z += current_block->steps_z;
if (st.counter_z > 0) {
out_bits |= (1<<Z_STEP_BIT);
st.counter_z -= st.event_count;
if (out_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS]--; }
else { sys.position[Z_AXIS]++; }
}
st.step_events_completed++; // Iterate step events
// While in block steps, check for de/ac-celeration events and execute them accordingly.
if (st.step_events_completed < current_block->step_event_count) {
if (sys.state == STATE_HOLD) {
