Hi,
I am having a weird problem with Arduino GRBL plotter project.
2 of 4 diagonal moves are not working correctly.
(Using universal G-code sender)
One axis movement:
Two axis movement (diagonal):
Seems that whenever one axis is set to '-' direction, the other can't be a '+' direction.
Any ideas what is going on 
I would check your motor wiring.
Hi @emosms1
You need to post the actual sketch (make sure it's added as code).
Which part of the 'sketch', all the GRBL files?
Motor wiring should be ok, they go ok Induvidually.
Just the mentioned 2 diagonal movements are wrong.
The machine also completes a homing procedure (going to X, Y zero) successfully.
No, there are cases were mis-wiring causes weird behavior.
Questions about GRBL are better asked on a CNC/GRBL forum.
I don't know how to check, all wires go to the designated pins.
Tested by moving the motors.
Both go clockwise and counterclockwise when moved +dir and -dir respectively.
Should I connect to a scope, logic analyser?
I know if there are stepper motor wiring issues (wrong phases) they can stall, go in reverse direction or the torque is not enough and they change direction when subjected to physical resistance .
Ok, you will need to provide more information, you have only provided minimal information.
Schematics, code (G-code), part numbers of hardware, pictures etc.
A scope is always handy. Put a probe on each of the motor pins.
... Don't have a scope with that many channels. Actually don't have any, I use PC sound card scope to check some analog/ audio circuits.
In general this is the project:
Board is Arduino nano, controlling it with universal G-code sender.
Arduino pins:
The guy on the video explains some issues of other nature, important config settings and finally runs the plotter.
He doesnt have that wrong diagonal movement.
As I remember the UGS g-code commands seem to be correct for all directions (incl diagonal movements).
I will post the exact commands later.
The sketch the Arduino runs.
Is this a build from a Instructions or YT guide?
I remapped all the pins (motor control, Z servo pwm, limit switches)
Edited the config.h, cpu_config.c, stepper.c files
I smell a rabbit hole here 
Lot of places where an error could sneak in.
Oof, too many hacks for me to deal with, any one of which could have gone wrong.
Btw, you can get really cheap logic analyzers which can capture lots of digital signals, and would help a lot to see what is going on.
The machine:
Wrong diagonal movement, UGS g-code:
G21G91G1X4Y-4F500 : X goes to '-' direction instead of '+'
G21G91G1X-4Y4F500 : Y goes to '-' direction instead of '+'
Does the same behavior happen with rapids? G0 instead of G1?
Example of the step-dir to 4 wire unipolar hack. It maps values 1-8 to bitmasks, assigning pins via port manipulation:
if (st.counter_y > st.exec_block->step_event_count) {
st.step_outbits |= (1<<Y_STEP_BIT);
st.counter_y -= st.exec_block->step_event_count;
if (st.exec_block->direction_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--;
//PORTC maps to Arduino analog pins 0 to 5. PORTB maps to Arduino digital pins 8 to 13. High bits (6 & 7) are not usable
//DDRB=255; // "A0, A1, A2, A3 for the Y axis"->D12,11,10,9
costyy=costyy-1;
if (costyy < 1) costyy=8; //PORTC->PORTB
if (costyy==1) PORTB=0B010000; //pin 3(0B1000)>12
if (costyy==2) PORTB=0B011000; //pin 3&2(0B1100)>12&11
if (costyy==3) PORTB=0B001000; //pin 2(0B0100)>11
if (costyy==4) PORTB=0B001100; //pin 2&1(0B0110)>11&10
if (costyy==5) PORTB=0B000100; //pin 1(0B0010)>10
if (costyy==6) PORTB=0B000110; //pin 1&0(0B0011)>10&9
if (costyy==7) PORTB=0B000010; //pin 0(0B0001)>9
if (costyy==8) PORTB=0B010010; //pin 0&3(0B1001)>9&12
The original bitmasks are in the comments. I switched these to a different port and different pins.
Moreover, the X axis has a longer bit mask, to address pins 4, 5, 6, 7 (needed longer bitmask..)
According to my logic, the GRBL 'g-code parser' (or whatever module it is) reads wrongly diagonal commands, where I use '+' and '-' movements simulatneously.
Smth. like when you multiply '+' and '-' number, the result is always negative...
The fact that it might be dependent on the exact controler pins (mby their bitmask representation) is kind of weird...
It is the same:
G91G0X-4Y4F500 - Y goes negative
G91G0X4Y-4F500 - X goes negative
It is very unlikely to be an error in the GRBL parser, unless that has been hacked as well.
It is most likely an error in the changes you have made. Perhaps you can show all the changes you made, and not just a small part.
I made both X and Y bitmasks remapping to be 10 digits format (added leading zeroes)
Works the same way :(.
> #define HOMING_CYCLE_0 (1<<X_AXIS)
> #define HOMING_CYCLE_1 (1<<Y_AXIS)
> //Enables single axis homing commands. $HX, $HY, and $HZ for X, Y, and Z-axis homing.
> //The full homing cycle is still invoked by the $H command.
> #define HOMING_SINGLE_AXIS_COMMANDS //EMNA - not working
/*
cpu_map_atmega328p.h - CPU and pin mapping configuration file
Part of Grbl
Copyright (c) 2012-2015 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/>.
*/
/* Grbl officially supports the Arduino Uno, but the other supplied pin mappings are
supplied by users, so your results may vary. This cpu_map file serves as a central
pin mapping settings file for AVR 328p used on the Arduino Uno. */
#ifdef GRBL_PLATFORM
#error "cpu_map already defined: GRBL_PLATFORM=" GRBL_PLATFORM
#endif
#define GRBL_PLATFORM "Atmega328p"
// Define serial port pins and interrupt vectors.
#define SERIAL_RX USART_RX_vect
#define SERIAL_UDRE USART_UDRE_vect
// Define step pulse output pins. NOTE: All step bit pins must be on the same port.
#define STEP_DDR DDRD
#define STEP_PORT PORTD
#define X_STEP_BIT 0//2 // Uno Digital Pin 2
#define Y_STEP_BIT 0//3 // Uno Digital Pin 3
#define Z_STEP_BIT 0//4 // Uno Digital Pin 4
#define STEP_MASK ((1<<X_STEP_BIT)|(1<<Y_STEP_BIT)|(1<<Z_STEP_BIT)) // All step bits
// Define step direction output pins. NOTE: All direction pins must be on the same port.
#define DIRECTION_DDR DDRD
#define DIRECTION_PORT PORTD
#define X_DIRECTION_BIT 0//5 // Uno Digital Pin 5
#define Y_DIRECTION_BIT 0//6 // Uno Digital Pin 6
#define Z_DIRECTION_BIT 0//7 // Uno Digital Pin 7
#define DIRECTION_MASK ((1<<X_DIRECTION_BIT)|(1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT)) // All direction bits
// Define stepper driver enable/disable output pin.
#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)
// Define homing/hard limit switch input pins and limit interrupt vectors.
// NOTE: All limit bit pins must be on the same port, but not on a port with other input pins (CONTROL).
#define LIMIT_DDR DDRC
#define LIMIT_PIN PINC
#define LIMIT_PORT PORTC
#define X_LIMIT_BIT 0 // Uno Digital Pin 9
#define Y_LIMIT_BIT 1 // Uno Digital Pin 10
#ifdef VARIABLE_SPINDLE // Z Limit pin and spindle enabled swapped to access hardware PWM on Pin 11.
#define Z_LIMIT_BIT 6 // Uno Digital Pin 12
#else
#define Z_LIMIT_BIT 6 // Uno Digital Pin 11
#endif
#define LIMIT_MASK ((1<<X_LIMIT_BIT)|(1<<Y_LIMIT_BIT)|(1<<Z_LIMIT_BIT)) // All limit bits
#define LIMIT_INT PCIE0 // Pin change interrupt enable pin
#define LIMIT_INT_vect PCINT0_vect
#define LIMIT_PCMSK PCMSK0 // Pin change interrupt register
// Define spindle enable and spindle direction output pins.
#define SPINDLE_ENABLE_DDR DDRB
#define SPINDLE_ENABLE_PORT PORTB
// Z Limit pin and spindle PWM/enable pin swapped to access hardware PWM on Pin 11.
#ifdef VARIABLE_SPINDLE
#ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
// If enabled, spindle direction pin now used as spindle enable, while PWM remains on D11.
#define SPINDLE_ENABLE_BIT 5 // Uno Digital Pin 13 (NOTE: D13 can't be pulled-high input due to LED.)
#else
#define SPINDLE_ENABLE_BIT 5 //pin 8// Uno Digital Pin 11
#endif
#else
#define SPINDLE_ENABLE_BIT 5 //pin13// Uno Digital Pin 12
#endif
#ifndef USE_SPINDLE_DIR_AS_ENABLE_PIN
#define SPINDLE_DIRECTION_DDR DDRD
#define SPINDLE_DIRECTION_PORT PORTD
#define SPINDLE_DIRECTION_BIT 2 // Uno Digital Pin 13 (NOTE: D13 can't be pulled-high input due to LED.)
#endif
// Define flood and mist coolant enable output pins.
// 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 COOLANT_FLOOD_DDR DDRC
#define COOLANT_FLOOD_PORT PORTC
#define COOLANT_FLOOD_BIT 5 // Uno Analog Pin 3
#ifdef ENABLE_M7 // Mist coolant disabled by default. See config.h to enable/disable.
#define COOLANT_MIST_DDR DDRC
#define COOLANT_MIST_PORT PORTC
#define COOLANT_MIST_BIT 4 // Uno Analog Pin 4
#endif
// Define user-control controls (cycle start, reset, feed hold) input pins.
// NOTE: All CONTROLs pins must be on the same port and not on a port with other input pins (limits).
#define CONTROL_DDR DDRC
#define CONTROL_PIN PINC
#define CONTROL_PORT PORTC
#define RESET_BIT 6//0 // Uno Analog Pin 0
#define FEED_HOLD_BIT 6//1 // Uno Analog Pin 1
#define CYCLE_START_BIT 6//2 // Uno Analog Pin 2
#define SAFETY_DOOR_BIT 6//1 // Uno Analog Pin 1 NOTE: Safety door is shared with feed hold. Enabled by config define.
#define CONTROL_INT PCIE1 // Pin change interrupt enable pin
#define CONTROL_INT_vect PCINT1_vect
#define CONTROL_PCMSK PCMSK1 // Pin change interrupt register
#define CONTROL_MASK ((1<<RESET_BIT)|(1<<FEED_HOLD_BIT)|(1<<CYCLE_START_BIT)|(1<<SAFETY_DOOR_BIT))
#define CONTROL_INVERT_MASK CONTROL_MASK // May be re-defined to only invert certain control pins.
// Define probe switch input pin.
#define PROBE_DDR DDRC
#define PROBE_PIN PINC
#define PROBE_PORT PORTC
#define PROBE_BIT 5 // Uno Analog Pin 5
#define PROBE_MASK (1<<PROBE_BIT)
// Start of PWM & Stepper Enabled Spindle
#ifdef VARIABLE_SPINDLE
// Advanced Configuration Below You should not need to touch these variables
#define PWM_MAX_VALUE 255.0
#define TCCRA_REGISTER TCCR2A
#define TCCRB_REGISTER TCCR2B
#define OCR_REGISTER OCR2B
#define COMB_BIT COM2B1
#define WAVE0_REGISTER WGM20
#define WAVE1_REGISTER WGM21
#define WAVE2_REGISTER WGM22
#define WAVE3_REGISTER WGM23
// NOTE: On the 328p, these must be the same as the SPINDLE_ENABLE settings.
#define SPINDLE_PWM_DDR DDRD
#define SPINDLE_PWM_PORT PORTD
#define SPINDLE_PWM_BIT 3 // Uno Digital Pin 11 //NE DAVA DA GO BARA6
#endif // End of VARIABLE_SPINDLE
/*
stepper.c - stepper motor driver: executes motion plans using stepper motors
Part of Grbl
Copyright (c) 2011-2015 Sungeun K. Jeon
Copyright (c) 2009-2011 Simen Svale Skogsrud
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/>.
*/
#include "grbl.h"
int costyx=1;
int costyy=1;
// Some useful constants.
#define DT_SEGMENT (1.0/(ACCELERATION_TICKS_PER_SECOND*60.0)) // min/segment
#define REQ_MM_INCREMENT_SCALAR 1.25
#define RAMP_ACCEL 0
#define RAMP_CRUISE 1
#define RAMP_DECEL 2
// Define Adaptive Multi-Axis Step-Smoothing(AMASS) levels and cutoff frequencies. The highest level
// frequency bin starts at 0Hz and ends at its cutoff frequency. The next lower level frequency bin
// starts at the next higher cutoff frequency, and so on. The cutoff frequencies for each level must
// be considered carefully against how much it over-drives the stepper ISR, the accuracy of the 16-bit
// timer, and the CPU overhead. Level 0 (no AMASS, normal operation) frequency bin starts at the
// Level 1 cutoff frequency and up to as fast as the CPU allows (over 30kHz in limited testing).
// NOTE: AMASS cutoff frequency multiplied by ISR overdrive factor must not exceed maximum step frequency.
// NOTE: Current settings are set to overdrive the ISR to no more than 16kHz, balancing CPU overhead
// and timer accuracy. Do not alter these settings unless you know what you are doing.
#define MAX_AMASS_LEVEL 3
// AMASS_LEVEL0: Normal operation. No AMASS. No upper cutoff frequency. Starts at LEVEL1 cutoff frequency.
#define AMASS_LEVEL1 (F_CPU/8000) // Over-drives ISR (x2). Defined as F_CPU/(Cutoff frequency in Hz)
#define AMASS_LEVEL2 (F_CPU/4000) // Over-drives ISR (x4)
#define AMASS_LEVEL3 (F_CPU/2000) // Over-drives ISR (x8)
// Stores the planner block Bresenham algorithm execution data for the segments in the segment
// buffer. Normally, this buffer is partially in-use, but, for the worst case scenario, it will
// never exceed the number of accessible stepper buffer segments (SEGMENT_BUFFER_SIZE-1).
// NOTE: This data is copied from the prepped planner blocks so that the planner blocks may be
// discarded when entirely consumed and completed by the segment buffer. Also, AMASS alters this
// data for its own use.
typedef struct {
uint8_t direction_bits;
uint32_t steps[N_AXIS];
uint32_t step_event_count;
} st_block_t;
static st_block_t st_block_buffer[SEGMENT_BUFFER_SIZE-1];
// Primary stepper segment ring buffer. Contains small, short line segments for the stepper
// algorithm to execute, which are "checked-out" incrementally from the first block in the
// planner buffer. Once "checked-out", the steps in the segments buffer cannot be modified by
// the planner, where the remaining planner block steps still can.
typedef struct {
uint16_t n_step; // Number of step events to be executed for this segment
uint8_t st_block_index; // Stepper block data index. Uses this information to execute this segment.
uint16_t cycles_per_tick; // Step distance traveled per ISR tick, aka step rate.
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
uint8_t amass_level; // Indicates AMASS level for the ISR to execute this segment
#else
uint8_t prescaler; // Without AMASS, a prescaler is required to adjust for slow timing.
#endif
} segment_t;
static segment_t segment_buffer[SEGMENT_BUFFER_SIZE];
// Stepper ISR data struct. Contains the running data for the main stepper ISR.
typedef struct {
// Used by the bresenham line algorithm
uint32_t counter_x, // Counter variables for the bresenham line tracer
counter_y,
counter_z;
#ifdef STEP_PULSE_DELAY
uint8_t step_bits; // Stores out_bits output to complete the step pulse delay
#endif
uint8_t execute_step; // Flags step execution for each interrupt.
uint8_t step_pulse_time; // Step pulse reset time after step rise
uint8_t step_outbits; // The next stepping-bits to be output
uint8_t dir_outbits; // EMNA
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
uint32_t steps[N_AXIS];
#endif
uint16_t step_count; // Steps remaining in line segment motion
uint8_t exec_block_index; // Tracks the current st_block index. Change indicates new block.
st_block_t *exec_block; // Pointer to the block data for the segment being executed
segment_t *exec_segment; // Pointer to the segment being executed
} stepper_t;
static stepper_t st;
// Step segment ring buffer indices
static volatile uint8_t segment_buffer_tail;
static uint8_t segment_buffer_head;
static uint8_t segment_next_head;
// Step and direction port invert masks.
static uint8_t step_port_invert_mask;
static uint8_t dir_port_invert_mask;
// Used to avoid ISR nesting of the "Stepper Driver Interrupt". Should never occur though.
static volatile uint8_t busy;
// Pointers for the step segment being prepped from the planner buffer. Accessed only by the
// main program. Pointers may be planning segments or planner blocks ahead of what being executed.
static plan_block_t *pl_block; // Pointer to the planner block being prepped
static st_block_t *st_prep_block; // Pointer to the stepper block data being prepped
// Segment preparation data struct. Contains all the necessary information to compute new segments
// based on the current executing planner block.
typedef struct {
uint8_t st_block_index; // Index of stepper common data block being prepped
uint8_t flag_partial_block; // Flag indicating the last block completed. Time to load a new one.
float steps_remaining;
float step_per_mm; // Current planner block step/millimeter conversion scalar
float req_mm_increment;
float dt_remainder;
uint8_t ramp_type; // Current segment ramp state
float mm_complete; // End of velocity profile from end of current planner block in (mm).
// NOTE: This value must coincide with a step(no mantissa) when converted.
float current_speed; // Current speed at the end of the segment buffer (mm/min)
float maximum_speed; // Maximum speed of executing block. Not always nominal speed. (mm/min)
float exit_speed; // Exit speed of executing block (mm/min)
float accelerate_until; // Acceleration ramp end measured from end of block (mm)
float decelerate_after; // Deceleration ramp start measured from end of block (mm)
} st_prep_t;
static st_prep_t prep;
/* BLOCK VELOCITY PROFILE DEFINITION
__________________________
/| |\ _________________ ^
/ | | \ /| |\ |
/ | | \ / | | \ s
/ | | | | | \ p
/ | | | | | \ e
+-----+------------------------+---+--+---------------+----+ e
| BLOCK 1 ^ BLOCK 2 | d
|
time -----> EXAMPLE: Block 2 entry speed is at max junction velocity
The planner block buffer is planned assuming constant acceleration velocity profiles and are
continuously joined at block junctions as shown above. However, the planner only actively computes
the block entry speeds for an optimal velocity plan, but does not compute the block internal
velocity profiles. These velocity profiles are computed ad-hoc as they are executed by the
stepper algorithm and consists of only 7 possible types of profiles: cruise-only, cruise-
deceleration, acceleration-cruise, acceleration-only, deceleration-only, full-trapezoid, and
triangle(no cruise).
maximum_speed (< nominal_speed) -> +
+--------+ <- maximum_speed (= nominal_speed) /|\
/ \ / | \
current_speed -> + \ / | + <- exit_speed
| + <- exit_speed / | |
+-------------+ current_speed -> +----+--+
time --> ^ ^ ^ ^
| | | |
decelerate_after(in mm) decelerate_after(in mm)
^ ^ ^ ^
| | | |
accelerate_until(in mm) accelerate_until(in mm)
The step segment buffer computes the executing block velocity profile and tracks the critical
parameters for the stepper algorithm to accurately trace the profile. These critical parameters
are shown and defined in the above illustration.
*/
// Stepper state initialization. Cycle should only start if the st.cycle_start flag is
// enabled. Startup init and limits call this function but shouldn't start the cycle.
void st_wake_up()
{
// Enable stepper drivers.
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) { STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT); }
else { STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT); }
if (sys.state & (STATE_CYCLE | STATE_HOMING)){
// Initialize stepper output bits
st.dir_outbits = dir_port_invert_mask;
st.step_outbits = step_port_invert_mask;
// Initialize step pulse timing from settings. Here to ensure updating after re-writing.
#ifdef STEP_PULSE_DELAY
// Set total step pulse time after direction pin set. Ad hoc computation from oscilloscope.
st.step_pulse_time = -(((settings.pulse_microseconds+STEP_PULSE_DELAY-2)*TICKS_PER_MICROSECOND) >> 3);
// Set delay between direction pin write and step command.
OCR0A = -(((settings.pulse_microseconds)*TICKS_PER_MICROSECOND) >> 3);
#else // Normal operation
// Set step pulse time. Ad hoc computation from oscilloscope. Uses two's complement.
st.step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
#endif
// Enable Stepper Driver Interrupt
TIMSK1 |= (1<<OCIE1A);
}
}
// Stepper shutdown
void st_go_idle()
{
// Disable Stepper Driver Interrupt. Allow Stepper Port Reset Interrupt to finish, if active.
TIMSK1 &= ~(1<<OCIE1A); // Disable Timer1 interrupt
TCCR1B = (TCCR1B & ~((1<<CS12) | (1<<CS11))) | (1<<CS10); // Reset clock to no prescaling.
busy = false;
// Set stepper driver idle state, disabled or enabled, depending on settings and circumstances.
bool pin_state = false; // Keep enabled.
if (((settings.stepper_idle_lock_time != 0xff) || sys_rt_exec_alarm) && sys.state != STATE_HOMING) {
// Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
// stop and not drift from residual inertial forces at the end of the last movement.
delay_ms(settings.stepper_idle_lock_time);
pin_state = true; // Override. Disable steppers.
}
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) { pin_state = !pin_state; } // Apply pin invert.
if (pin_state) { STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT); }
else { STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT); }
}
/* "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of Grbl. Grbl employs
the venerable Bresenham line algorithm to manage and exactly synchronize multi-axis moves.
Unlike the popular DDA algorithm, the Bresenham algorithm is not susceptible to numerical
round-off errors and only requires fast integer counters, meaning low computational overhead
and maximizing the Arduino's capabilities. However, the downside of the Bresenham algorithm
is, for certain multi-axis motions, the non-dominant axes may suffer from un-smooth step
pulse trains, or aliasing, which can lead to strange audible noises or shaking. This is
particularly noticeable or may cause motion issues at low step frequencies (0-5kHz), but
is usually not a physical problem at higher frequencies, although audible.
To improve Bresenham multi-axis performance, Grbl uses what we call an Adaptive Multi-Axis
Step Smoothing (AMASS) algorithm, which does what the name implies. At lower step frequencies,
AMASS artificially increases the Bresenham resolution without effecting the algorithm's
innate exactness. AMASS adapts its resolution levels automatically depending on the step
frequency to be executed, meaning that for even lower step frequencies the step smoothing
level increases. Algorithmically, AMASS is acheived by a simple bit-shifting of the Bresenham
step count for each AMASS level. For example, for a Level 1 step smoothing, we bit shift
the Bresenham step event count, effectively multiplying it by 2, while the axis step counts
remain the same, and then double the stepper ISR frequency. In effect, we are allowing the
non-dominant Bresenham axes step in the intermediate ISR tick, while the dominant axis is
stepping every two ISR ticks, rather than every ISR tick in the traditional sense. At AMASS
Level 2, we simply bit-shift again, so the non-dominant Bresenham axes can step within any
of the four ISR ticks, the dominant axis steps every four ISR ticks, and quadruple the
stepper ISR frequency. And so on. This, in effect, virtually eliminates multi-axis aliasing
issues with the Bresenham algorithm and does not significantly alter Grbl's performance, but
in fact, more efficiently utilizes unused CPU cycles overall throughout all configurations.
AMASS retains the Bresenham algorithm exactness by requiring that it always executes a full
Bresenham step, regardless of AMASS Level. Meaning that for an AMASS Level 2, all four
intermediate steps must be completed such that baseline Bresenham (Level 0) count is always
retained. Similarly, AMASS Level 3 means all eight intermediate steps must be executed.
Although the AMASS Levels are in reality arbitrary, where the baseline Bresenham counts can
be multiplied by any integer value, multiplication by powers of two are simply used to ease
CPU overhead with bitshift integer operations.
This interrupt is simple and dumb by design. All the computational heavy-lifting, as in
determining accelerations, is performed elsewhere. This interrupt pops pre-computed segments,
defined as constant velocity over n number of steps, from the step segment buffer and then
executes them by pulsing the stepper pins appropriately via the Bresenham algorithm. This
ISR is supported by The Stepper Port Reset Interrupt which it uses to reset the stepper port
after each pulse. The bresenham line tracer algorithm controls all stepper outputs
simultaneously with these two interrupts.
NOTE: This interrupt must be as efficient as possible and complete before the next ISR tick,
which for Grbl must be less than 33.3usec (@30kHz ISR rate). Oscilloscope measured time in
ISR is 5usec typical and 25usec maximum, well below requirement.
NOTE: This ISR expects at least one step to be executed per segment.
*/
// TODO: Replace direct updating of the int32 position counters in the ISR somehow. Perhaps use smaller
// int8 variables and update position counters only when a segment completes. This can get complicated
// with probing and homing cycles that require true real-time positions.
ISR(TIMER1_COMPA_vect)
{
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
if (busy) { return; } // The busy-flag is used to avoid reentering this interrupt
// Set the direction pins a couple of nanoseconds before we step the steppers
//DIRECTION_PORT = (DIRECTION_PORT & ~DIRECTION_MASK) | (st.dir_outbits & DIRECTION_MASK);
// Then pulse the stepping pins
#ifdef STEP_PULSE_DELAY
st.step_bits = (STEP_PORT & ~STEP_MASK) | st.step_outbits; // Store out_bits to prevent overwriting.
#else // Normal operation
STEP_PORT = (STEP_PORT & ~STEP_MASK) | st.step_outbits;
#endif
// Enable step pulse reset timer so that The Stepper Port Reset Interrupt can reset the signal after
// exactly settings.pulse_microseconds microseconds, independent of the main Timer1 prescaler.
TCNT0 = st.step_pulse_time; // Reload Timer0 counter
TCCR0B = (1<<CS01); // Begin Timer0. Full speed, 1/8 prescaler
busy = true;
sei(); // Re-enable interrupts to allow Stepper Port Reset Interrupt to fire on-time.
// NOTE: The remaining code in this ISR will finish before returning to main program.
// If there is no step segment, attempt to pop one from the stepper buffer
if (st.exec_segment == NULL) {
// Anything in the buffer? If so, load and initialize next step segment.
if (segment_buffer_head != segment_buffer_tail) {
// Initialize new step segment and load number of steps to execute
st.exec_segment = &segment_buffer[segment_buffer_tail];
#ifndef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
// With AMASS is disabled, set timer prescaler for segments with slow step frequencies (< 250Hz).
TCCR1B = (TCCR1B & ~(0x07<<CS10)) | (st.exec_segment->prescaler<<CS10);
#endif
// Initialize step segment timing per step and load number of steps to execute.
OCR1A = st.exec_segment->cycles_per_tick;
st.step_count = st.exec_segment->n_step; // NOTE: Can sometimes be zero when moving slow.
// If the new segment starts a new planner block, initialize stepper variables and counters.
// NOTE: When the segment data index changes, this indicates a new planner block.
if ( st.exec_block_index != st.exec_segment->st_block_index ) {
st.exec_block_index = st.exec_segment->st_block_index;
st.exec_block = &st_block_buffer[st.exec_block_index];
// Initialize Bresenham line and distance counters
st.counter_x = st.counter_y = st.counter_z = (st.exec_block->step_event_count >> 1);
}
//st.dir_outbits = st.exec_block->direction_bits ^ dir_port_invert_mask;
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
// With AMASS enabled, adjust Bresenham axis increment counters according to AMASS level.
st.steps[X_AXIS] = st.exec_block->steps[X_AXIS] >> st.exec_segment->amass_level;
st.steps[Y_AXIS] = st.exec_block->steps[Y_AXIS] >> st.exec_segment->amass_level;
st.steps[Z_AXIS] = st.exec_block->steps[Z_AXIS] >> st.exec_segment->amass_level;
#endif
} else {
// Segment buffer empty. Shutdown.
st_go_idle();
bit_true_atomic(sys_rt_exec_state,EXEC_CYCLE_STOP); // Flag main program for cycle end
return; // Nothing to do but exit.
}
}
// Check probing state.
probe_state_monitor();
// Reset step out bits.
st.step_outbits = 0;
st.exec_block->direction_bits = st.exec_block->direction_bits ^ dir_port_invert_mask;
// Execute step displacement profile by Bresenham line algorithm
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
st.counter_x += st.steps[X_AXIS];
#else
st.counter_x += st.exec_block->steps[X_AXIS];
#endif
if (st.counter_x > st.exec_block->step_event_count) {
st.step_outbits |= (1<<X_STEP_BIT);
st.counter_x -= st.exec_block->step_event_count;
if (st.exec_block->direction_bits & (1<<X_DIRECTION_BIT)) { sys.position[X_AXIS]--;
//https://docs.arduino.cc/retired/hacking/software/PortManipulation/
//UDR0=65; //PORTD maps to Arduino digital pins 0 to 7.
//DDRD=255; // "2,3,4,5 digital pins to the axis X"->D7,6,5,4
costyx=costyx-1;
if (costyx < 1) costyx=8; //PORTD
if (costyx==1) PORTD=0B10000000; //pin 5(0B100000)>7
if (costyx==2) PORTD=0B11000000; //pin 5&4(0B110000)>7&6
if (costyx==3) PORTD=0B01000000; //pin 4(0B010000)>6
if (costyx==4) PORTD=0B01100000; //pin 4&3(0B011000)>6&5
if (costyx==5) PORTD=0B00100000; //pin 3(0B001000)>5
if (costyx==6) PORTD=0B00110000; //pin 3&2(0B001100)>5&4
if (costyx==7) PORTD=0B00010000; //pin 2(0B000100)>4
if (costyx==8) PORTD=0B10010000; //pin 2&5(0B100100)>4&7
}
else { sys.position[X_AXIS]++;
// UDR0=66;
//DDRD=255;
costyx=costyx+1;
if (costyx > 8) costyx=1;
if (costyx==1) PORTD=0B10000000; //same as above
if (costyx==2) PORTD=0B11000000;
if (costyx==3) PORTD=0B01000000;
if (costyx==4) PORTD=0B01100000;
if (costyx==5) PORTD=0B00100000;
if (costyx==6) PORTD=0B00110000;
if (costyx==7) PORTD=0B00010000;
if (costyx==8) PORTD=0B10010000;
}
}
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
st.counter_y += st.steps[Y_AXIS];
#else
st.counter_y += st.exec_block->steps[Y_AXIS];
#endif
if (st.counter_y > st.exec_block->step_event_count) {
st.step_outbits |= (1<<Y_STEP_BIT);
st.counter_y -= st.exec_block->step_event_count;
if (st.exec_block->direction_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--;
//PORTC maps to Arduino analog pins 0 to 5. PORTB maps to Arduino digital pins 8 to 13. High bits (6 & 7) are not usable
//DDRB=255; // "A0, A1, A2, A3 for the Y axis"->D12,11,10,9
costyy=costyy-1;
if (costyy < 1) costyy=8; //PORTC->PORTB
if (costyy==1) PORTB=0B00010000; //pin 3(0B1000)>12
if (costyy==2) PORTB=0B00011000; //pin 3&2(0B1100)>12&11
if (costyy==3) PORTB=0B00001000; //pin 2(0B0100)>11
if (costyy==4) PORTB=0B00001100; //pin 2&1(0B0110)>11&10
if (costyy==5) PORTB=0B00000100; //pin 1(0B0010)>10
if (costyy==6) PORTB=0B00000110; //pin 1&0(0B0011)>10&9
if (costyy==7) PORTB=0B00000010; //pin 0(0B0001)>9
if (costyy==8) PORTB=0B00010010; //pin 0&3(0B1001)>9&12
}
else { sys.position[Y_AXIS]++;
//DDRB=255;
costyy=costyy+1;
if (costyy > 8) costyy=1;
if (costyy==1) PORTB=0B00010000; //same as above
if (costyy==2) PORTB=0B00011000;
if (costyy==3) PORTB=0B00001000;
if (costyy==4) PORTB=0B00001100;
if (costyy==5) PORTB=0B00000100;
if (costyy==6) PORTB=0B00000110;
if (costyy==7) PORTB=0B00000010;
if (costyy==8) PORTB=0B00010010;
}
}
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
st.counter_z += st.steps[Z_AXIS];
#else
st.counter_z += st.exec_block->steps[Z_AXIS];
#endif
if (st.counter_z > st.exec_block->step_event_count) {
st.step_outbits |= (1<<Z_STEP_BIT);
st.counter_z -= st.exec_block->step_event_count;
if (st.exec_block->direction_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS]--; }
else { sys.position[Z_AXIS]++; }
}
// During a homing cycle, lock out and prevent desired axes from moving.
if (sys.state == STATE_HOMING) { st.step_outbits &= sys.homing_axis_lock; }
st.step_count--; // Decrement step events count
if (st.step_count == 0) {
// Segment is complete. Discard current segment and advance segment indexing.
st.exec_segment = NULL;
if ( ++segment_buffer_tail == SEGMENT_BUFFER_SIZE) { segment_buffer_tail = 0; }
}
st.step_outbits ^= step_port_invert_mask; // Apply step port invert mask
busy = false;
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
}
/* The Stepper Port Reset Interrupt: Timer0 OVF interrupt handles the falling edge of the step
pulse. This should always trigger before the next Timer1 COMPA interrupt and independently
finish, if Timer1 is disabled after completing a move.
NOTE: Interrupt collisions between the serial and stepper interrupts can cause delays by
a few microseconds, if they execute right before one another. Not a big deal, but can
cause issues at high step rates if another high frequency asynchronous interrupt is
added to Grbl.
*/
// This interrupt is enabled by ISR_TIMER1_COMPAREA when it sets the motor port bits to execute
// a step. This ISR resets the motor port after a short period (settings.pulse_microseconds)
// completing one step cycle.
ISR(TIMER0_OVF_vect)
{
// Reset stepping pins (leave the direction pins)
STEP_PORT = (STEP_PORT & ~STEP_MASK) | (step_port_invert_mask & STEP_MASK);
TCCR0B = 0; // Disable Timer0 to prevent re-entering this interrupt when it's not needed.
}
#ifdef STEP_PULSE_DELAY
// This interrupt is used only when STEP_PULSE_DELAY is enabled. Here, the step pulse is
// initiated after the STEP_PULSE_DELAY time period has elapsed. The ISR TIMER2_OVF interrupt
// will then trigger after the appropriate settings.pulse_microseconds, as in normal operation.
// The new timing between direction, step pulse, and step complete events are setup in the
// st_wake_up() routine.
ISR(TIMER0_COMPA_vect)
{
STEP_PORT = st.step_bits; // Begin step pulse.
}
#endif
// Generates the step and direction port invert masks used in the Stepper Interrupt Driver.
void st_generate_step_dir_invert_masks()
{
uint8_t idx;
step_port_invert_mask = 0;
dir_port_invert_mask = 0;
for (idx=0; idx<N_AXIS; idx++) {
if (bit_istrue(settings.step_invert_mask,bit(idx))) { step_port_invert_mask |= get_step_pin_mask(idx); }
if (bit_istrue(settings.dir_invert_mask,bit(idx))) { dir_port_invert_mask |= get_direction_pin_mask(idx); }
}
}
// Reset and clear stepper subsystem variables
void st_reset()
{
// Initialize stepper driver idle state.
st_go_idle();
// Initialize stepper algorithm variables.
memset(&prep, 0, sizeof(st_prep_t));
memset(&st, 0, sizeof(stepper_t));
st.exec_segment = NULL;
pl_block = NULL; // Planner block pointer used by segment buffer
segment_buffer_tail = 0;
segment_buffer_head = 0; // empty = tail
segment_next_head = 1;
busy = false;
st_generate_step_dir_invert_masks();
// Initialize step and direction port pins.
STEP_PORT = (STEP_PORT & ~STEP_MASK) | step_port_invert_mask;
//DIRECTION_PORT = (DIRECTION_PORT & ~DIRECTION_MASK) | dir_port_invert_mask;
}
// Initialize and start the stepper motor subsystem
void stepper_init()
{
// Configure step and direction interface pins
STEP_DDR |= STEP_MASK;
STEPPERS_DISABLE_DDR |= 1<<STEPPERS_DISABLE_BIT;
DIRECTION_DDR |= DIRECTION_MASK;
// Configure Timer 1: Stepper Driver Interrupt
TCCR1B &= ~(1<<WGM13); // waveform generation = 0100 = CTC
TCCR1B |= (1<<WGM12);
TCCR1A &= ~((1<<WGM11) | (1<<WGM10));
TCCR1A &= ~((1<<COM1A1) | (1<<COM1A0) | (1<<COM1B1) | (1<<COM1B0)); // Disconnect OC1 output
// TCCR1B = (TCCR1B & ~((1<<CS12) | (1<<CS11))) | (1<<CS10); // Set in st_go_idle().
// TIMSK1 &= ~(1<<OCIE1A); // Set in st_go_idle().
// Configure Timer 0: Stepper Port Reset Interrupt
TIMSK0 &= ~((1<<OCIE0B) | (1<<OCIE0A) | (1<<TOIE0)); // Disconnect OC0 outputs and OVF interrupt.
TCCR0A = 0; // Normal operation
TCCR0B = 0; // Disable Timer0 until needed
TIMSK0 |= (1<<TOIE0); // Enable Timer0 overflow interrupt
#ifdef STEP_PULSE_DELAY
TIMSK0 |= (1<<OCIE0A); // Enable Timer0 Compare Match A interrupt
#endif
}
// Called by planner_recalculate() when the executing block is updated by the new plan.
void st_update_plan_block_parameters()
{
if (pl_block != NULL) { // Ignore if at start of a new block.
prep.flag_partial_block = true;
pl_block->entry_speed_sqr = prep.current_speed*prep.current_speed; // Update entry speed.
pl_block = NULL; // Flag st_prep_segment() to load new velocity profile.
}
}
/* Prepares step segment buffer. Continuously called from main program.
The segment buffer is an intermediary buffer interface between the execution of steps
by the stepper algorithm and the velocity profiles generated by the planner. The stepper
algorithm only executes steps within the segment buffer and is filled by the main program
when steps are "checked-out" from the first block in the planner buffer. This keeps the
step execution and planning optimization processes atomic and protected from each other.
The number of steps "checked-out" from the planner buffer and the number of segments in
the segment buffer is sized and computed such that no operation in the main program takes
longer than the time it takes the stepper algorithm to empty it before refilling it.
Currently, the segment buffer conservatively holds roughly up to 40-50 msec of steps.
NOTE: Computation units are in steps, millimeters, and minutes.
*/
void st_prep_buffer()
{
if (sys.state & (STATE_HOLD|STATE_MOTION_CANCEL|STATE_SAFETY_DOOR)) {
// Check if we still need to generate more segments for a motion suspend.
if (prep.current_speed == 0.0) { return; } // Nothing to do. Bail.
}
while (segment_buffer_tail != segment_next_head) { // Check if we need to fill the buffer.
// Determine if we need to load a new planner block or if the block has been replanned.
if (pl_block == NULL) {
pl_block = plan_get_current_block(); // Query planner for a queued block
if (pl_block == NULL) { return; } // No planner blocks. Exit.
// Check if the segment buffer completed the last planner block. If so, load the Bresenham
// data for the block. If not, we are still mid-block and the velocity profile was updated.
if (prep.flag_partial_block) {
prep.flag_partial_block = false; // Reset flag
} else {
// Increment stepper common data index to store new planner block data.
if ( ++prep.st_block_index == (SEGMENT_BUFFER_SIZE-1) ) { prep.st_block_index = 0; }
// Prepare and copy Bresenham algorithm segment data from the new planner block, so that
// when the segment buffer completes the planner block, it may be discarded when the
// segment buffer finishes the prepped block, but the stepper ISR is still executing it.
st_prep_block = &st_block_buffer[prep.st_block_index];
st_prep_block->direction_bits = pl_block->direction_bits;
#ifndef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
st_prep_block->steps[X_AXIS] = pl_block->steps[X_AXIS];
st_prep_block->steps[Y_AXIS] = pl_block->steps[Y_AXIS];
st_prep_block->steps[Z_AXIS] = pl_block->steps[Z_AXIS];
st_prep_block->step_event_count = pl_block->step_event_count;
#else
// With AMASS enabled, simply bit-shift multiply all Bresenham data by the max AMASS
// level, such that we never divide beyond the original data anywhere in the algorithm.
// If the original data is divided, we can lose a step from integer roundoff.
st_prep_block->steps[X_AXIS] = pl_block->steps[X_AXIS] << MAX_AMASS_LEVEL;
st_prep_block->steps[Y_AXIS] = pl_block->steps[Y_AXIS] << MAX_AMASS_LEVEL;
st_prep_block->steps[Z_AXIS] = pl_block->steps[Z_AXIS] << MAX_AMASS_LEVEL;
st_prep_block->step_event_count = pl_block->step_event_count << MAX_AMASS_LEVEL;
#endif
// Initialize segment buffer data for generating the segments.
prep.steps_remaining = pl_block->step_event_count;
prep.step_per_mm = prep.steps_remaining/pl_block->millimeters;
prep.req_mm_increment = REQ_MM_INCREMENT_SCALAR/prep.step_per_mm;
prep.dt_remainder = 0.0; // Reset for new planner block
if (sys.state & (STATE_HOLD|STATE_MOTION_CANCEL|STATE_SAFETY_DOOR)) {
// Override planner block entry speed and enforce deceleration during feed hold.
prep.current_speed = prep.exit_speed;
pl_block->entry_speed_sqr = prep.exit_speed*prep.exit_speed;
}
else { prep.current_speed = sqrt(pl_block->entry_speed_sqr); }
}
/* ---------------------------------------------------------------------------------
Compute the velocity profile of a new planner block based on its entry and exit
speeds, or recompute the profile of a partially-completed planner block if the
planner has updated it. For a commanded forced-deceleration, such as from a feed
hold, override the planner velocities and decelerate to the target exit speed.
*/
prep.mm_complete = 0.0; // Default velocity profile complete at 0.0mm from end of block.
float inv_2_accel = 0.5/pl_block->acceleration;
if (sys.state & (STATE_HOLD|STATE_MOTION_CANCEL|STATE_SAFETY_DOOR)) { // [Forced Deceleration to Zero Velocity]
// Compute velocity profile parameters for a feed hold in-progress. This profile overrides
// the planner block profile, enforcing a deceleration to zero speed.
prep.ramp_type = RAMP_DECEL;
// Compute decelerate distance relative to end of block.
float decel_dist = pl_block->millimeters - inv_2_accel*pl_block->entry_speed_sqr;
if (decel_dist < 0.0) {
// Deceleration through entire planner block. End of feed hold is not in this block.
prep.exit_speed = sqrt(pl_block->entry_speed_sqr-2*pl_block->acceleration*pl_block->millimeters);
} else {
prep.mm_complete = decel_dist; // End of feed hold.
prep.exit_speed = 0.0;
}
} else { // [Normal Operation]
// Compute or recompute velocity profile parameters of the prepped planner block.
prep.ramp_type = RAMP_ACCEL; // Initialize as acceleration ramp.
prep.accelerate_until = pl_block->millimeters;
prep.exit_speed = plan_get_exec_block_exit_speed();
float exit_speed_sqr = prep.exit_speed*prep.exit_speed;
float intersect_distance =
0.5*(pl_block->millimeters+inv_2_accel*(pl_block->entry_speed_sqr-exit_speed_sqr));
if (intersect_distance > 0.0) {
if (intersect_distance < pl_block->millimeters) { // Either trapezoid or triangle types
// NOTE: For acceleration-cruise and cruise-only types, following calculation will be 0.0.
prep.decelerate_after = inv_2_accel*(pl_block->nominal_speed_sqr-exit_speed_sqr);
if (prep.decelerate_after < intersect_distance) { // Trapezoid type
prep.maximum_speed = sqrt(pl_block->nominal_speed_sqr);
if (pl_block->entry_speed_sqr == pl_block->nominal_speed_sqr) {
// Cruise-deceleration or cruise-only type.
prep.ramp_type = RAMP_CRUISE;
} else {
// Full-trapezoid or acceleration-cruise types
prep.accelerate_until -= inv_2_accel*(pl_block->nominal_speed_sqr-pl_block->entry_speed_sqr);
}
} else { // Triangle type
prep.accelerate_until = intersect_distance;
prep.decelerate_after = intersect_distance;
prep.maximum_speed = sqrt(2.0*pl_block->acceleration*intersect_distance+exit_speed_sqr);
}
} else { // Deceleration-only type
prep.ramp_type = RAMP_DECEL;
// prep.decelerate_after = pl_block->millimeters;
prep.maximum_speed = prep.current_speed;
}
} else { // Acceleration-only type
prep.accelerate_until = 0.0;
// prep.decelerate_after = 0.0;
prep.maximum_speed = prep.exit_speed;
}
}
}
// Initialize new segment
segment_t *prep_segment = &segment_buffer[segment_buffer_head];
// Set new segment to point to the current segment data block.
prep_segment->st_block_index = prep.st_block_index;
/*------------------------------------------------------------------------------------
Compute the average velocity of this new segment by determining the total distance
traveled over the segment time DT_SEGMENT. The following code first attempts to create
a full segment based on the current ramp conditions. If the segment time is incomplete
when terminating at a ramp state change, the code will continue to loop through the
progressing ramp states to fill the remaining segment execution time. However, if
an incomplete segment terminates at the end of the velocity profile, the segment is
considered completed despite having a truncated execution time less than DT_SEGMENT.
The velocity profile is always assumed to progress through the ramp sequence:
acceleration ramp, cruising state, and deceleration ramp. Each ramp's travel distance
may range from zero to the length of the block. Velocity profiles can end either at
the end of planner block (typical) or mid-block at the end of a forced deceleration,
such as from a feed hold.
*/
float dt_max = DT_SEGMENT; // Maximum segment time
float dt = 0.0; // Initialize segment time
float time_var = dt_max; // Time worker variable
float mm_var; // mm-Distance worker variable
float speed_var; // Speed worker variable
float mm_remaining = pl_block->millimeters; // New segment distance from end of block.
float minimum_mm = mm_remaining-prep.req_mm_increment; // Guarantee at least one step.
if (minimum_mm < 0.0) { minimum_mm = 0.0; }
do {
switch (prep.ramp_type) {
case RAMP_ACCEL:
// NOTE: Acceleration ramp only computes during first do-while loop.
speed_var = pl_block->acceleration*time_var;
mm_remaining -= time_var*(prep.current_speed + 0.5*speed_var);
if (mm_remaining < prep.accelerate_until) { // End of acceleration ramp.
// Acceleration-cruise, acceleration-deceleration ramp junction, or end of block.
mm_remaining = prep.accelerate_until; // NOTE: 0.0 at EOB
time_var = 2.0*(pl_block->millimeters-mm_remaining)/(prep.current_speed+prep.maximum_speed);
if (mm_remaining == prep.decelerate_after) { prep.ramp_type = RAMP_DECEL; }
else { prep.ramp_type = RAMP_CRUISE; }
prep.current_speed = prep.maximum_speed;
} else { // Acceleration only.
prep.current_speed += speed_var;
}
break;
case RAMP_CRUISE:
// NOTE: mm_var used to retain the last mm_remaining for incomplete segment time_var calculations.
// NOTE: If maximum_speed*time_var value is too low, round-off can cause mm_var to not change. To
// prevent this, simply enforce a minimum speed threshold in the planner.
mm_var = mm_remaining - prep.maximum_speed*time_var;
if (mm_var < prep.decelerate_after) { // End of cruise.
// Cruise-deceleration junction or end of block.
time_var = (mm_remaining - prep.decelerate_after)/prep.maximum_speed;
mm_remaining = prep.decelerate_after; // NOTE: 0.0 at EOB
prep.ramp_type = RAMP_DECEL;
} else { // Cruising only.
mm_remaining = mm_var;
}
break;
default: // case RAMP_DECEL:
// NOTE: mm_var used as a misc worker variable to prevent errors when near zero speed.
speed_var = pl_block->acceleration*time_var; // Used as delta speed (mm/min)
if (prep.current_speed > speed_var) { // Check if at or below zero speed.
// Compute distance from end of segment to end of block.
mm_var = mm_remaining - time_var*(prep.current_speed - 0.5*speed_var); // (mm)
if (mm_var > prep.mm_complete) { // Deceleration only.
mm_remaining = mm_var;
prep.current_speed -= speed_var;
break; // Segment complete. Exit switch-case statement. Continue do-while loop.
}
} // End of block or end of forced-deceleration.
time_var = 2.0*(mm_remaining-prep.mm_complete)/(prep.current_speed+prep.exit_speed);
mm_remaining = prep.mm_complete;
}
dt += time_var; // Add computed ramp time to total segment time.
if (dt < dt_max) { time_var = dt_max - dt; } // **Incomplete** At ramp junction.
else {
if (mm_remaining > minimum_mm) { // Check for very slow segments with zero steps.
// Increase segment time to ensure at least one step in segment. Override and loop
// through distance calculations until minimum_mm or mm_complete.
dt_max += DT_SEGMENT;
time_var = dt_max - dt;
} else {
break; // **Complete** Exit loop. Segment execution time maxed.
}
}
} while (mm_remaining > prep.mm_complete); // **Complete** Exit loop. Profile complete.
/* -----------------------------------------------------------------------------------
Compute segment step rate, steps to execute, and apply necessary rate corrections.
NOTE: Steps are computed by direct scalar conversion of the millimeter distance
remaining in the block, rather than incrementally tallying the steps executed per
segment. This helps in removing floating point round-off issues of several additions.
However, since floats have only 7.2 significant digits, long moves with extremely
high step counts can exceed the precision of floats, which can lead to lost steps.
Fortunately, this scenario is highly unlikely and unrealistic in CNC machines
supported by Grbl (i.e. exceeding 10 meters axis travel at 200 step/mm).
*/
float steps_remaining = prep.step_per_mm*mm_remaining; // Convert mm_remaining to steps
float n_steps_remaining = ceil(steps_remaining); // Round-up current steps remaining
float last_n_steps_remaining = ceil(prep.steps_remaining); // Round-up last steps remaining
prep_segment->n_step = last_n_steps_remaining-n_steps_remaining; // Compute number of steps to execute.
// Bail if we are at the end of a feed hold and don't have a step to execute.
if (prep_segment->n_step == 0) {
if (sys.state & (STATE_HOLD|STATE_MOTION_CANCEL|STATE_SAFETY_DOOR)) {
// Less than one step to decelerate to zero speed, but already very close. AMASS
// requires full steps to execute. So, just bail.
prep.current_speed = 0.0; // NOTE: (=0.0) Used to indicate completed segment calcs for hold.
prep.dt_remainder = 0.0;
prep.steps_remaining = n_steps_remaining;
pl_block->millimeters = prep.steps_remaining/prep.step_per_mm; // Update with full steps.
plan_cycle_reinitialize();
return; // Segment not generated, but current step data still retained.
}
}
// Compute segment step rate. Since steps are integers and mm distances traveled are not,
// the end of every segment can have a partial step of varying magnitudes that are not
// executed, because the stepper ISR requires whole steps due to the AMASS algorithm. To
// compensate, we track the time to execute the previous segment's partial step and simply
// apply it with the partial step distance to the current segment, so that it minutely
// adjusts the whole segment rate to keep step output exact. These rate adjustments are
// typically very small and do not adversely effect performance, but ensures that Grbl
// outputs the exact acceleration and velocity profiles as computed by the planner.
dt += prep.dt_remainder; // Apply previous segment partial step execute time
float inv_rate = dt/(last_n_steps_remaining - steps_remaining); // Compute adjusted step rate inverse
prep.dt_remainder = (n_steps_remaining - steps_remaining)*inv_rate; // Update segment partial step time
// Compute CPU cycles per step for the prepped segment.
uint32_t cycles = ceil( (TICKS_PER_MICROSECOND*1000000*60)*inv_rate ); // (cycles/step)
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
// Compute step timing and multi-axis smoothing level.
// NOTE: AMASS overdrives the timer with each level, so only one prescalar is required.
if (cycles < AMASS_LEVEL1) { prep_segment->amass_level = 0; }
else {
if (cycles < AMASS_LEVEL2) { prep_segment->amass_level = 1; }
else if (cycles < AMASS_LEVEL3) { prep_segment->amass_level = 2; }
else { prep_segment->amass_level = 3; }
cycles >>= prep_segment->amass_level;
prep_segment->n_step <<= prep_segment->amass_level;
}
if (cycles < (1UL << 16)) { prep_segment->cycles_per_tick = cycles; } // < 65536 (4.1ms @ 16MHz)
else { prep_segment->cycles_per_tick = 0xffff; } // Just set the slowest speed possible.
#else
// Compute step timing and timer prescalar for normal step generation.
if (cycles < (1UL << 16)) { // < 65536 (4.1ms @ 16MHz)
prep_segment->prescaler = 1; // prescaler: 0
prep_segment->cycles_per_tick = cycles;
} else if (cycles < (1UL << 19)) { // < 524288 (32.8ms@16MHz)
prep_segment->prescaler = 2; // prescaler: 8
prep_segment->cycles_per_tick = cycles >> 3;
} else {
prep_segment->prescaler = 3; // prescaler: 64
if (cycles < (1UL << 22)) { // < 4194304 (262ms@16MHz)
prep_segment->cycles_per_tick = cycles >> 6;
} else { // Just set the slowest speed possible. (Around 4 step/sec.)
prep_segment->cycles_per_tick = 0xffff;
}
}
#endif
// Segment complete! Increment segment buffer indices.
segment_buffer_head = segment_next_head;
if ( ++segment_next_head == SEGMENT_BUFFER_SIZE ) { segment_next_head = 0; }
// Setup initial conditions for next segment.
if (mm_remaining > prep.mm_complete) {
// Normal operation. Block incomplete. Distance remaining in block to be executed.
pl_block->millimeters = mm_remaining;
prep.steps_remaining = steps_remaining;
} else {
// End of planner block or forced-termination. No more distance to be executed.
if (mm_remaining > 0.0) { // At end of forced-termination.
// Reset prep parameters for resuming and then bail. Allow the stepper ISR to complete
// the segment queue, where realtime protocol will set new state upon receiving the
// cycle stop flag from the ISR. Prep_segment is blocked until then.
prep.current_speed = 0.0; // NOTE: (=0.0) Used to indicate completed segment calcs for hold.
prep.dt_remainder = 0.0;
prep.steps_remaining = ceil(steps_remaining);
pl_block->millimeters = prep.steps_remaining/prep.step_per_mm; // Update with full steps.
plan_cycle_reinitialize();
return; // Bail!
} else { // End of planner block
// The planner block is complete. All steps are set to be executed in the segment buffer.
pl_block = NULL; // Set pointer to indicate check and load next planner block.
plan_discard_current_block();
}
}
}
}
// Called by realtime status reporting to fetch the current speed being executed. This value
// however is not exactly the current speed, but the speed computed in the last step segment
// in the segment buffer. It will always be behind by up to the number of segment blocks (-1)
// divided by the ACCELERATION TICKS PER SECOND in seconds.
#ifdef REPORT_REALTIME_RATE
float st_get_realtime_rate()
{
if (sys.state & (STATE_CYCLE | STATE_HOMING | STATE_HOLD | STATE_MOTION_CANCEL | STATE_SAFETY_DOOR)){
return prep.current_speed;
}
return 0.0f;
}
#endif
Seems it is not some common issue but smth more complex.
Probably the algorithm that smooths out multi-axis movement is messed up with my arbitrary bitmask pin reasignment onto the 4-wire motor control hack.
Reverted back to the original pins and the 'original' hacked library:
The motor pins are:
Z servo and limit swhitches:
Now seems to work correctly, but I have to rewire my veroboard shield 
A chaotic beauty 
So you're on top of this, excellent! And the error remains unknown, or..?
