Grbl Mega Plasma Firmware

CNC Motion Control Firmware for MecanicaLG Motion Control Boards based on Arduino ATMega2560. Optimized for CNC Plasma Cutting and improving functionalities related with it process.

[TOC]

This library is written based on grbl-Mega a documentation can be found here

GCODE documentation can be found here:

Gcode Dictionary by Duet3d

Gcode by RepRap

Arduino functions used in this project are documented and explained here

---

Features

• All original GRBL features left intact
• Added new commands and error codes
• Added new libraries
• Built in Arc Voltage Torch Height Control. Uses A0 to read arc voltage from the plasma cutter and makes adjustments on a 1ms intervol.

Configuration

Chip select in file config.h

// To use with RAMPS 1.4 Board, comment out the above defines and uncomment the next two defines
#define DEFAULTS_RAMPS_BOARD
#define CPU_MAP_2560_RAMPS_BOARD

New libraries List

New libraries are added in grbl.h

// Integration features
#include "adc.h"
#include "timer.h"
#include "thc.h"
#include "thc_reports.h"
#include "ports.h"
#include "pwm.h"

Library	Description
adc	Handle ADC module in Atmega2560
timer	Handle Timer2 configuration and interruption
thc	THC Control
thc_reports	THC status reports and debugging functions
ports	Ports management
pwm	Handle pwm output module

Global Variables Added

Variable	Type	Description	Declared on
analogVal	volatile uint16_t	Value to store analog result from ADC	adc
hysteresis	volatile uint16_t	Allowable voltage deviation	thc
analogSetVal	volatile uint16_t	Value to stabilize in THC	thc
thcWorking	bool	THC working status	thc

---

THC Functionalities

ADC use

For THC purpose there is a ADC channel, it can be selected in file adc.h defined in variable ADC_THC_CHANNEL_SELECT by default its value is equal to 3.

// ADC THC Chanel selector
// Do not set above 15! You will overrun other parts of ADMUX.
        #define ADC_THC_CHANNEL_SELECT 3;

For configuartion use the adc_setup() function and for start first convertion use start_adc_convertion() defined in adc.c.

Timer use

Timer2 module was used to handle THC timing, all function are implemented in timer.c file

timer_setup() function is used to configure timer and the interruption subroutine can be found here to.

THC work mode

Reports

Command "?" sends the next response from Grbl the implementation can be found in report.c in fuction report_realtime_status()

<Idle|MPos:0.000,0.000,0.000|FS:0,0|Pn:XYZ|WCO:0.000,0.000,0.000>

When THC is working variable thcWorking is set true and the "?" command response is

<Idle|MPos:0.000,0.000,0.000|FS:0,0|Pn:XYZ|WCO:0.000,0.000,0.000|THC:0,0>

The THC param bring the fallow information

THC:<analogSetVal>,<analogVal>

Command $$ give the information about several params including $133,its show the value of nominal voltage of THC, the implementation is in report.c in function report_status_message(), it calls report_thc() from thc_repots.c

Ark Ok signal

---

Ports Functionalities

The port functionalities implemented allow to carry out new operations such as waiting for signal or reading and writing on pins. This allows adding new functionalities to the hardware such as valve control or waiting for the Arc Ok signal. Also a pwm control and a alarm system are implemented.

M17: Stepper Enable

Reference implementation and documentation can be found here:

Command use cases

M17 // Enable power on all stepper motors

M17 x // Enable power on specific stepper motors

Parameters

<x> Stepper motors to enable [X,Y,Z]

M18: Stepper Disable

Reference implementation and documentation can be found here:

Command use cases

M18 // Disable power on all stepper motors

M18 x // Disable power on specific stepper motors

Parameters

<x> Stepper motors to disable [X,Y,Z]

M42: Switch I/O pin

Reference implementation and documentation can be found here:

Command use cases

M42 Pxx Mx // Set pin mode

M42 Pxx Sx // Set pin state

M42 Pxx R // Read pin

Parameters

P<xx> Pin number

<xx> This value must be between 1 and 99

M<x> Pin mode

Mode	Description
0	Set pin as INPUT make the bit of DDR to 0, and the bit of PORT to 0
1	Set pin as INPUT_PULLUP make the bit of DDR to 0, and the bit of PORT to 1
2	Set pin as OUTPUT make the bit of DDR to 1

S<x> Pin state

State	Description
0	0 logic
1	1 logic

R Read

Response	Description
LOW	If pin is a 0 logic
HIGH	If pin is 1 logic

Response

Response	Description
ok	Command executed successfully
error:60	Pin locked

Example

M42 P7 M2		// Set pin 7 to digital out
M42 P7 S1       // Set pin 7 to 1 logic
M42 P7 R		// Read pin state

//-----------------------------------
As same way you can send those commands as a single block folowing the priority
M42 P7 M2 S1   // Set pin 7 to digital out and to 1 logic state
M42 P7 R       // Read pin state

M226: Waint for pin Async

Reference implementation and documentation can be found here.

This process is executed asynchronously, this means that when receiving the command, the movement will be stopped after execute all the buffer stored and will not be restored until the pin wait for the state is completed.

Command use cases

M226 Pxx Sx // Waint for pin state

Parameters

P<xx> Pin number

<xx> This value must be between 1 and 99

S<x> Pin state

State	Description
0	0 logic
1	1 logic

Response

Response	Description
ok	Command executed successfully
error:60	Pin locked

Example

G01 X50 F50 // Move to X 50 position with feedrate of 50
M226 P37 S1 // Waint for pin 37 to change to 1 logic satus, at this point movement isn't stoped untli finsih previous movements
G01 X0 F200 // Move to X 0 position, the movement is restarted when pin 37 change mode

M227: Waint for pin Sync

Same params as M226 but in this case movement is stoped as well as command arrives

Example

G01 X50 F50 // Move to X 50 position
M226 P37 S1 // Waint for pin 37 to change to 1 logic satus, at this point movement is stoped
G01 X0 F200 // Move to X 0 position, the movement is restarted when pin 37 change mode

M219: PWM

For pwm purpose are used timer 4 and 5 module it can be used to drive a servo motor, laser module or digital-analog converter (DAC).

For this purpose are used the next pinout:

Pin Port	Digital pin	Chip pin	Alternate Function
PH5	8	17	OC4C(Output Compare and PWM Output C for Timer/Counter4)
PH4	7	16	OC4B(Output Compare and PWM Output B for Timer/Counter4)
PH3	6	15	OC4A(Output Compare and PWM Output A for Timer/Counter4)
PL5	44	40	OC5C(Output Compare and PWM Output C for Timer/Counter5)
PL4	45	39	OC5B(Output Compare and PWM Output B for Timer/Counter5)

Command use cases

M219 Tx Mx // Configure timer mode

M219 Tx Nx // Configure timer max value for set period

M219 Tx Cx Vx // Configure timer channel value

M219 Tx Cx D // Disable timer channel

Parameters

T<x> Timer number

<x> This value must be between 4 or 5

M<x> Timer mode

<x> This value must be between 0 and 5

PWM mode is configured as Fast PWM with OCRnA register as TOP value in timer 5 case and ICRn in timer 4 case.

Mode	Description
0	No clock source(Timer/Counter stopped)
1	Set timer divisor to 1 (proper frequency)
2	Set timer divisor to 8
3	Set timer divisor to 64
4	Set timer divisor to 256
5	Set timer divisor to 1024 (only abailable in timer 4)

N<x> Maximum count value

<x> This value must be between 0 (pwm disabled) and 0xffff(maximun 16-bit register size)

Output frequency can be calculated as $$ f_{OCnxPWM}=f_{clk_{IO}}/N*(1+TOP) $$

C<x> Channe select

<x> This value must be between 1 and 3 in case of timer 4 and in timer 5 case must be 2 or 3

D Used for disable channel

V<x> This value is for set duty cycle in channel $$ DutyCycle=(OCRnx+1)/N $$

Example:
-----------------------------------------------------------------------------------------
*-> Fclk = 16MHz
*-> in mode 3 the divor is x64 then f=16MHz/64=0.25MHz=250KHz
*-> if we set TOP value N=256 then output frequency is 250KHz/256=0.97656KHz=976.6Hz 
*-> And if a channel has configured a value of 180 the the duty_cycle=(OCRnx+1)/N=(180+1)/256=0.707=70.7%

Example

M219 T5 M3		      // Congirure timer 5 as Fast PWM prescaler x64
M219 T5 N256          // Set maximum count value in timer 5
M219 T5 C2 V180	      // Set timer 5 channel 2 output as 70.7% duty cycle
M219 T5 C2 D		  // Disable channel 2 timer 5	

Alarms System

There are some signals with priority of atention than trigger alarms, this alarms are for exaple when the tourch crash and fall or other works params are wrong, when one of those alams are detected the movement is stoped to fix the problem fisically, when all is put in order by the operator then the movement is restored manually by a command and its restored from the last coordenate to don't loose the cout.

Alarm Message	Meaning	Port/Pin
[MSG:Power Fault]	Power Source fault	PB5
[MSG:Alarm Out Servo X1]	Alarm OUT Servo X1	PB7
[MSG:Alarm Out Servo X2]	Alarm OUT Servo X2	PK5
[MSG:Alarm Out Servo Y]	Alarm OUT Servo Y	PK6
[MSG:Alarm Tourch Signal]	Tourch Signal	PB6

This alarms are located in ports B and K are handle by interruption subroutines by port status change.

M229: Initialize all alarms

Initialize all alarms, port B and K cases. When this command is recived alarms pin are configured and interrupts enabled.

Command use case

M229

M230: Disable all alarms

Disable all alarms, port B and K cases. When this command is recived interrupts by port change are disabled.

Command use case

M230

M231: Enable alarm mask

Enable alarm mask, port B or K cases. Allows detect port change interrupt in this pin.

Command use case

M231 <n><x>

Parameters

<n> Port of alarms (must be B or K)

<x> Alarm pin (must be between 5 and 7 in port B and in case of port K must be 5 or 6)

Example

M231 B5 Enable port B pin 5 alarm interrupt by port change state

M232: Disable alarm mask

Disable alarm mask, port B or K cases. Disable detect port change interrupt in this pin.

Command use case

M232 <n><x>

Parameters

<n> Port of alarms (must be B or K)

<x> Alarm pin (must be between 5 and 7 in port B and in case of port K must be 5 or 6)

Example

M232 K5 Disable port K pin 5 alarm interrupt by port change state

~ : Restore movement after port alarm stop

This command is implemented in grbl by default, we addeded a function to restore alarm once movement is enabled.

---

How I implemented it

Normally grbl is not written to interpret the M command and its format with multiple params its why it was necessary to modify the file gcode.h to process the blocks in separated functions

// Added ignore process blocks M command implemented
  while (line[char_counter] != 0 && !(letter=='M' && (int_value==17 || int_value==18 || int_value==42 || int_value==219 || (int_value>=227 && int_value<=233))))

Command M17

Implemented in port.c in stepperEnable() uses varible declared in cpu_map.h for steppers control and assume the enable is active in 1 logic because the driver circuit used.

 STEPPER_DISABLE_PORT(0) |= (1 << STEPPER_DISABLE_BIT(0));
 STEPPER_DISABLE_PORT(1) |= (1 << STEPPER_DISABLE_BIT(1));
 STEPPER_DISABLE_PORT(2) |= (1 << STEPPER_DISABLE_BIT(2));

Command M18

Implemented in port.c in stepperEnable() uses varible declared in cpu_map.h for steppers control and assume the disable is active in 0 logic because the driver circuit used.

 STEPPER_DISABLE_PORT(0) &= ~(1 << STEPPER_DISABLE_BIT(0));
 STEPPER_DISABLE_PORT(1) &= ~(1 << STEPPER_DISABLE_BIT(1));
 STEPPER_DISABLE_PORT(2) &= ~(1 << STEPPER_DISABLE_BIT(2));

Command M42

This command is implemented in ports.c specifically in the function ports_manage() who is in charge of processing the parameters. Within this function were used:

pinMode()

digitalWrite()

digitalRead()

Its full implementation can be seen here

This functions is called from gcode.c in the switch cases from M commands

// Implementing M42
//-----------------------------------
          case 42:
//Execute M42 function and if the pin is blocked or bad format is reported return error
          result = ports_manage(line);
            if(result==2){FAIL(STATUS_GCODE_PIN_LOCKED);}
            else if(result==1){FAIL(STATUS_EXPECTED_COMMAND_LETTER);}
          break;

ports_manage() function returns 3 states

State	Meaning
1	Format problem
2	Pin blocked
3	Ok

If the function detect and error it will be reported by serial communication.

Command M226

The function is called in the same way

  		   //-----------------------------------
           // Implementing M226
          //-----------------------------------
          case 226:
          result = waintForPinAsync(line);
          if(result==2){FAIL(STATUS_GCODE_PIN_LOCKED);}
          else if(result==1){FAIL(STATUS_INVALID_STATEMENT);}
          break;

The waintForPinSync() function is implemented as a while loop, it reads the pin state and keep in loop until its value is equal to the state pram, its params are extracted from line param, it is the command block recibed for M226.

 protocol_buffer_synchronize(); // Sync and finish all remaining buffered motions before moving on.
protocol_execute_realtime(); // Execute suspend.
  while(digitalRead(pinVal)!= stateVal){

  }
protocol_exec_rt_system();  // Executes run-time commands

protocol_buffer_synchronize() documentation can be found here.

protocol_execute_realtime()documentation can be found here.

protocol_exec_rt_system()documentation can be found here.

Command M227

This command is implemented similar as M226 the main difference is the synchronism, in this case when command is received the movement is stopped immediately

protocol_execute_realtime(); // Execute suspend.
  while(digitalRead(pinVal)!= stateVal){

  }
protocol_exec_rt_system();  // Executes run-time commands

Command 219

For this command implementation was consider the spindle_control.c file and the function analogWrite() for manage the configuration.

The set up PWM algorithm is described here:

• Configure Timer to frequency :

For timer configuration are used the function pwmTimerFreq() which set the fraquency divisor using the clock select bits (CS) these control the clock prescaler, pwmConfCount() according to the mode we can set maximum count value to adjust period setting the OCRnA / ICRn registers value and pwmConfTimer() set the waveform generation mode bits (WGM) these control the overall mode of the timer (These bits are split between TCCRnA and TCCRnBregisters)

• Configure output pins for channels with duty cycle :

The functionpwmChannelEnable() set the DDRx to set the pin as pull-up output and OCRxnset the value for duty cycle, then the COMnx1 allows to set the channel as clear on compare match OCnx and set at BOTTOM this is th non-inveting mode.

• Disable PWM output

In this case by setting COMnx1/COMnx0 to logical 0 then we set the normal port operation, OCnA/OCnB/OCnC disconnected

Alarms System

This system is handle by interrupt so we have the ISR(PCINT0_vect) implemented in port.c for port B change pin interrupt and ISR(PCINT2_vect) already implemented by grbl using pins 1,2 and 3.

For initialize alarms we use alarmsInit() function explained in M229 command, then when a alarm is triggered we read the port status and make a OR logical operation whit PORTB_PCINTERRUPT_STATE_MASK to check which alarm is in wrong state, you can modify this mask in port.c file deppending of your hardware.

Then we set the global variable alarmTriggered to true, it tell as when a alarm was detected, and store in activeAlarmPort and activeAlarmBit the respective values of the alarm case to re-enable it when movement is restored. Then execute alarmDisable() function with this updated values to avoid a re-triggered of the interrupt and stop movement with system_set_exec_state_flag(EXEC_FEED_HOLD) function, a documentation can be found here .

For alarm feedback its used the function report_feedback_message() implemented in report.c.

New codes has been added for this purpose defined in report.h.

// Alarms code implemented
#define MESSAGE_POWER_SOURCE_FAULT 15
#define MESSAGE_ALARM_OUT_SERVO_X1 16
#define MESSAGE_ALARM_OUT_SERVO_X2 17
#define MESSAGE_ALARM_OUT_SERVO_Y 18
#define MESSAGE_ALARM_TOURCH_SIGNAL 19

Command M229

Command is implemented in port.c file in function alarmsInit().

For enable all interrupts we follow the confuration path:

• Configure DDRx register to set pin s as inputs.
• Configure PORTx register to enable internal pull-up resistors, normal high operation.
• Configure PCMSK register to enable specific pins of the pin change interrupt.
• Set specific bit in PCICR to enable pin change interrupt.

Command M230

Command is implemented in port.c file in function alarmsDisable().

Disable pin change interrupt in PCICR register.

Command ~

To the original grbl function we added in serial.c ,in the ISR function for serial comunication ISR(SERIAL_RX) a check for variable alarmTriggered and if its true enable the alarm with alarmEnable().

case CMD_CYCLE_START:   system_set_exec_state_flag(EXEC_CYCLE_START);  // Set as true
                        if(alarmTriggered)alarmEnable(activeAlarmPort,activeAlarmBit);
                        break; 

error:60 Pin Locked

Define error code in report.h as

#define STATUS_GCODE_PIN_LOCKED 60

ports_manage declared in ports.c function returns a boolean value

bool ports_manage(char *line)

This criteria is definded in ports.c in function

bool pinBlocked(uint8_t pin)

Who tell us if pin is blocked or not, you can add some pins in this function declaration to allow or not its use. In array of constants workPin declared in ports.c and the constants are defined in ports.h.

---

Licence

This is copyrighted software that is released under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 license

The unofficial summary is:

You can use it as it is for non-commercial purposes. If you modify it, you must make the modifications public and attribute the original source to me.

(If you want to license it for commerical use, please contact me.)

---

You can also see others useful repos related with THC implementation and other stuff

Repo description	Link
ArdunioTHC	https://github.com/regeg/ArdunioTHC
Plasma THC	https://github.com/grblHAL/Plugin_plasma/
DIY built CNC Plasma with Arduino THC (Torch Height Controller)	https://github.com/regeg/ArdunioTHC
CNC Motion Control Firmware for XmotionCNC Motion Control Boards or Arduino UNO DIY setup. Focused on CNC Plasma Cutting.	https://github.com/UnfinishedBusiness/XmotionFirmware
Arduino based THC that reads plasma cutter voltage and send Up and Down signals to Plasma Torch Actuator to adjust voltage to target value.	https://github.com/HaleDesign/TorchHeightController
CNC plugin for the plasma torch height controlling on the base of Arduino (ATmega328P MCU)	https://github.com/ussserrr/torch-height-control
Plasma/THC plugin	https://github.com/grblHAL/Plugin_plasma
GRBL-LPC1769	https://github.com/gnea/grbl-LPC
DIY Arduino based Torch Height Controller	https://github.com/bluestang123/plasmacnc
CNC plugin for the plasma torch height controlling on the base of Arduino (ATmega328P MCU)	https://github.com/ussserrr/torch-height-control
LinuxCNC	https://github.com/LinuxCNC/linuxcnc
Marlin Firmware	https://github.com/MarlinFirmware/Marlin
Repetier Firmware	https://github.com/repetier/Repetier-Firmware

---

If you want to support me you can do it in

• buymeacoffe

As many other, brought to you with 🖤 ,lack of 🛏️ and lots of ☕ under 🎧.

Powered by MecanicaLG and AlaSoluciones ©2022