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add servo motor support using cprezzi and DWiskow approach #811

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add servo motor support using cprezzi and DWiskow approach #811

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10 changes: 10 additions & 0 deletions grbl/config.h
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Original file line number Diff line number Diff line change
Expand Up @@ -367,6 +367,16 @@
// NOTE: Requires USE_SPINDLE_DIR_AS_ENABLE_PIN to be enabled.
// #define SPINDLE_ENABLE_OFF_WITH_ZERO_SPEED // Default disabled. Uncomment to enable.

// If you use a servo instead of a spindle (like on EggBot or pen plotter), you need to uncomment this option.
// This will set the PWM frequency to 61Hz and limit the PWM range to 0.5 - 2.5ms, as used by most servos.
// #define SPINDLE_IS_SERVO // Default disabled. Uncomment to enable.

#define SERVO_SHORT 7 // set min pulse duration to (7 = 0.5ms, 15 = 1.03ms, 20=1.40ms)
#define SERVO_LONG 38 // set max pulse duration (38 = 2.49ms, 31 = 2.05ms)
#define SERVO_RANGE (SERVO_LONG-SERVO_SHORT)
// #define SERVO_INVERT 1 // Uncomment to invert servo direction


// With this enabled, Grbl sends back an echo of the line it has received, which has been pre-parsed (spaces
// removed, capitalized letters, no comments) and is to be immediately executed by Grbl. Echoes will not be
// sent upon a line buffer overflow, but should for all normal lines sent to Grbl. For example, if a user
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15 changes: 10 additions & 5 deletions grbl/cpu_map.h
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Original file line number Diff line number Diff line change
Expand Up @@ -141,11 +141,16 @@

// Prescaled, 8-bit Fast PWM mode.
#define SPINDLE_TCCRA_INIT_MASK ((1<<WGM20) | (1<<WGM21)) // Configures fast PWM mode.
// #define SPINDLE_TCCRB_INIT_MASK (1<<CS20) // Disable prescaler -> 62.5kHz
// #define SPINDLE_TCCRB_INIT_MASK (1<<CS21) // 1/8 prescaler -> 7.8kHz (Used in v0.9)
// #define SPINDLE_TCCRB_INIT_MASK ((1<<CS21) | (1<<CS20)) // 1/32 prescaler -> 1.96kHz
#define SPINDLE_TCCRB_INIT_MASK (1<<CS22) // 1/64 prescaler -> 0.98kHz (J-tech laser)


#ifdef SPINDLE_IS_SERVO
#define SPINDLE_TCCRB_INIT_MASK ((1<<CS22) | (1<<CS21) | (1<<CS20)) // 1/1024 prescaler -> 61Hz (for Servo)
#else
// #define SPINDLE_TCCRB_INIT_MASK (1<<CS20) // Disable prescaler -> 62.5kHz
// #define SPINDLE_TCCRB_INIT_MASK (1<<CS21) // 1/8 prescaler -> 7.8kHz (Used in v0.9)
// #define SPINDLE_TCCRB_INIT_MASK ((1<<CS21) | (1<<CS20)) // 1/32 prescaler -> 1.96kHz
#define SPINDLE_TCCRB_INIT_MASK (1<<CS22) // 1/64 prescaler -> 0.98kHz (J-tech laser)
#endif

// NOTE: On the 328p, these must be the same as the SPINDLE_ENABLE settings.
#define SPINDLE_PWM_DDR DDRB
#define SPINDLE_PWM_PORT PORTB
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34 changes: 31 additions & 3 deletions grbl/spindle_control.c
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,6 @@

#include "grbl.h"


#ifdef VARIABLE_SPINDLE
static float pwm_gradient; // Precalulated value to speed up rpm to PWM conversions.
#endif
Expand Down Expand Up @@ -113,6 +112,16 @@ void spindle_stop()
SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT); // Set pin to low
#endif
#endif
if (!(settings.flags & BITFLAG_LASER_MODE)) {
#ifdef SPINDLE_IS_SERVO
SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT); // Ensure PWM output is enabled.
#ifdef SERVO_INVERT
SPINDLE_OCR_REGISTER = SERVO_LONG;
#else
SPINDLE_OCR_REGISTER = SERVO_SHORT;
#endif
#endif
}
}


Expand All @@ -135,11 +144,19 @@ void spindle_stop()
}
#else
if (pwm_value == SPINDLE_PWM_OFF_VALUE) {
SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); // Disable PWM. Output voltage is zero.
if (!(settings.flags & BITFLAG_LASER_MODE)) {
#ifndef SPINDLE_IS_SERVO
SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); // Disable PWM. Output voltage is zero.
#else
spindle_stop();
#endif
} else {
SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); // Disable PWM. Output voltage is zero.
}
} else {
SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT); // Ensure PWM output is enabled.
}
#endif
#endif
}


Expand Down Expand Up @@ -212,6 +229,17 @@ void spindle_stop()
sys.spindle_speed = rpm;
pwm_value = floor((rpm-settings.rpm_min)*pwm_gradient) + SPINDLE_PWM_MIN_VALUE;
}

if (!(settings.flags & BITFLAG_LASER_MODE)) {
#ifdef SPINDLE_IS_SERVO
#ifdef SERVO_INVERT
pwm_value = floor(SERVO_LONG - rpm*(SERVO_RANGE/(settings.rpm_max-settings.rpm_min)));
#else
pwm_value = floor(rpm*(SERVO_RANGE/(settings.rpm_max-settings.rpm_min))+SERVO_SHORT);
#endif
#endif
}

return(pwm_value);
}

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