Added step pulse delay after direction set (Compile-time option only). Updated read me.
Added a compile-time only experimental feature that creates a user-specified time delay between a step pulse and a direction pin set (in config.h). This is for users with hardware-specific issues (opto-couplers) that need more than a few microseconds between events, which can lead to slowly progressing step drift after many many direction changes. We suggest to try the hack/fix posted in the Wiki before using this, as this experimental feature may cause Grbl to take a performance hit at high step rates and about complex curves.
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Sonny Jeon
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41
config.h
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41
config.h
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@ -75,7 +75,7 @@
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// entering g-code into grbl, i.e. locating part zero or simple manual machining. If the axes drift,
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// grbl has no way to know this has happened, since stepper motors are open-loop control. Depending
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// on the machine, this parameter may need to be larger or smaller than the default time.
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// NOTE: If commented out, the delay will not be compiled.
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// NOTE: If set to zero, the delay will not be compiled.
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#define STEPPER_IDLE_LOCK_TIME 25 // (milliseconds) - Integer > 0
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// The temporal resolution of the acceleration management subsystem. Higher number give smoother
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@ -114,19 +114,36 @@
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// time step. Also, keep in mind that the Arduino delay timer is not very accurate for long delays.
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#define DWELL_TIME_STEP 50 // Integer (1-255) (milliseconds)
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// FOR ADVANCED USERS ONLY: Toggles XON/XOFF software flow control for serial communications.
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// Officially not supported due to problems involving the Atmega8U2 USB-to-serial chips on all
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// new and future Arduinos. The firmware on these chips do not support XON/XOFF flow control
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// characters and the intermediate buffer in the chips cause latency and overflow problems with
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// standard terminal programs. However, using specifically-programmed UI's to manage this latency
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// problem has been confirmed to work, as well as, using older FTDI FT232RL-based Arduinos
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// (Duemilanove) since their firmaware correctly manage the XON/XOFF characters. Other unconfirmed
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// methods include using an FTDI board/cable or directly communicate on the RX/TX pins on the
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// Arduino, both of which circumvent the Atmega8U2 chip altogether. In any case, please report any
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// successes to grbl administrators!
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// ---------------------------------------------------------------------------------------
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// FOR ADVANCED USERS ONLY:
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// Toggles XON/XOFF software flow control for serial communications. Not officially supported
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// due to problems involving the Atmega8U2 USB-to-serial chips on current Arduinos. The firmware
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// on these chips do not support XON/XOFF flow control characters and the intermediate buffer
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// in the chips cause latency and overflow problems with standard terminal programs. However,
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// using specifically-programmed UI's to manage this latency problem has been confirmed to work.
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// As well as, older FTDI FT232RL-based Arduinos(Duemilanove) are known to work with standard
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// terminal programs since their firmware correctly manage these XON/XOFF characters. In any
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// case, please report any successes to grbl administrators!
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#define ENABLE_XONXOFF 0 // Boolean. Default disabled.
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// -----------------------------------------------
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// Creates a delay between the direction pin setting and corresponding step pulse by creating
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// another interrupt (Timer2 compare) to manage it. The main Grbl interrupt (Timer1 compare)
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// sets the direction pins, and does not immediately set the stepper pins, as it would in
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// normal operation. The Timer2 compare fires next to set the stepper pins after the step
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// pulse delay time, and Timer2 overflow will complete the step pulse, except now delayed
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// by the step pulse time plus the step pulse delay. (Thanks langwadt for the idea!)
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// This is an experimental feature that should only be used if your setup requires a longer
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// delay between direction and step pin settings (some opto coupler based drivers), as it may
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// adversely effect Grbl's high-end performance (>10kHz). Please notify Grbl administrators
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// of your successes or difficulties, as we will monitor this and possibly integrate this as a
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// standard feature for future releases. However, we suggest to first try our direction delay
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// hack/solution posted in the Wiki involving inverting the stepper pin mask.
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// NOTE: If set greater than zero, step pulse delay will be compiled and enabled. Also, the
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// total delay added with the Grbl settings pulse microseconds must not exceed 127 ms.
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#define STEP_PULSE_DELAY 0 // Step pulse delay in microseconds. Default disabled.
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// ---------------------------------------------------------------------------------------
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// TODO: The following options are set as compile-time options for now, until the next EEPROM
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// settings version has solidified.
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6
readme.textile
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6
readme.textile
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@ -19,9 +19,11 @@ Grbl includes full acceleration management with look ahead. That means the contr
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- Program stop(M0,M1*,M2,M30) initial support. Optional stop to do.
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- System reset re-initializes grbl without resetting the Arduino and retains machine/home position and work coordinates.
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- Restructured planner and stepper modules to become independent and ready for future features.
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- Planned features: Jog mode, status reporting, runtime settings such as toggling block delete, XON/XOFF flow control.
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- Reduce serial read buffer to 128 characters and increased write buffer to 64 characters.
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- Reduced serial read buffer to 128 characters and increased write buffer to 64 characters.
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- Misc bug fixes and removed deprecated acceleration enabled code.
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- Planned features: Jog mode, full-featured status reporting, runtime settings such as toggling block delete.
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- Advanced compile-time options: Up to 6 work coordinate systems(G54-G59), XON/XOFF flow control (limited support), direction and step pulse time delay.
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*Important note for Atmega 168 users:* Going forward, support for Atmega 168 will be dropped due to its limited memory and speed. However, legacy Grbl v0.51 "in the branch called 'v0_51' is still available for use.
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40
stepper.c
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40
stepper.c
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@ -62,6 +62,10 @@ static uint8_t step_pulse_time; // Step pulse reset time after step rise
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static uint8_t out_bits; // The next stepping-bits to be output
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static volatile uint8_t busy; // True when SIG_OUTPUT_COMPARE1A is being serviced. Used to avoid retriggering that handler.
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#if STEP_PULSE_DELAY > 0
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static uint8_t step_bits; // Stores out_bits output to complete the step pulse delay
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#endif
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// __________________________
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// /| |\ _________________ ^
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// / | | \ /| |\ |
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@ -86,8 +90,16 @@ static void st_wake_up()
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{
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// Initialize stepper output bits
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out_bits = (0) ^ (settings.invert_mask);
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// Set step pulse time. Ad hoc computation from oscilloscope.
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step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
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// Initialize step pulse timing from settings. Here to ensure updating after re-writing.
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#if STEP_PULSE_DELAY > 0
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// Set total step pulse time after direction pin set. Ad hoc computation from oscilloscope.
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step_pulse_time = -(((settings.pulse_microseconds+STEP_PULSE_DELAY-2)*TICKS_PER_MICROSECOND) >> 3);
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// Set delay between direction pin write and step command.
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OCR2A = -(((settings.pulse_microseconds)*TICKS_PER_MICROSECOND) >> 3);
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#else // Normal operation
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// Set step pulse time. Ad hoc computation from oscilloscope. Uses two's complement.
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step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
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#endif
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// Enable steppers by resetting the stepper disable port
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STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
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// Enable stepper driver interrupt
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@ -101,7 +113,7 @@ void st_go_idle()
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TIMSK1 &= ~(1<<OCIE1A);
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// Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
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// stop and not drift from residual inertial forces at the end of the last movement.
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#ifdef STEPPER_IDLE_LOCK_TIME
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#if STEPPER_IDLE_LOCK_TIME > 0
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_delay_ms(STEPPER_IDLE_LOCK_TIME);
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#endif
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// Disable steppers by setting stepper disable
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@ -133,7 +145,11 @@ ISR(TIMER1_COMPA_vect)
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// Set the direction pins a couple of nanoseconds before we step the steppers
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STEPPING_PORT = (STEPPING_PORT & ~DIRECTION_MASK) | (out_bits & DIRECTION_MASK);
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// Then pulse the stepping pins
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STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | out_bits;
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#if STEP_PULSE_DELAY > 0
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step_bits = (STEPPING_PORT & ~STEP_MASK) | out_bits; // Store out_bits to prevent overwriting.
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#else // Normal operation
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STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | out_bits;
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#endif
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// Enable step pulse reset timer so that The Stepper Port Reset Interrupt can reset the signal after
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// exactly settings.pulse_microseconds microseconds, independent of the main Timer1 prescaler.
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TCNT2 = step_pulse_time; // Reload timer counter
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@ -298,6 +314,18 @@ ISR(TIMER2_OVF_vect)
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TCCR2B = 0; // Disable Timer2 to prevent re-entering this interrupt when it's not needed.
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}
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#if STEP_PULSE_DELAY > 0
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// This interrupt is used only when STEP_PULSE_DELAY is enabled. Here, the step pulse is
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// initiated after the STEP_PULSE_DELAY time period has elapsed. The ISR TIMER2_OVF interrupt
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// will then trigger after the appropriate settings.pulse_microseconds, as in normal operation.
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// The new timing between direction, step pulse, and step complete events are setup in the
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// st_wake_up() routine.
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ISR(TIMER2_COMPA_vect)
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{
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STEPPING_PORT = step_bits; // Begin step pulse.
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}
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#endif
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// Reset and clear stepper subsystem variables
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void st_reset()
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{
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@ -330,6 +358,10 @@ void st_init()
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TCCR2B = 0; // Disable timer until needed.
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TIMSK2 |= (1<<TOIE2);
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#if STEP_PULSE_DELAY > 0
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TIMSK2 |= (1<<OCIE2A); // Enable Timer2 Compare Match A interrupt
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#endif
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// Start in the idle state
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st_go_idle();
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}
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