heatbed audible noise suppression using short fast PWM pulses with
variable duty
This commit is contained in:
DRracer
parent
ce128e012f
commit
a16de83535
5 changed files with 167 additions and 75 deletions
109
Firmware/heatbed_pwm.cpp
Executable file
109
Firmware/heatbed_pwm.cpp
Executable file
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@ -0,0 +1,109 @@
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include "io_atmega2560.h"
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// All this is about silencing the heat bed, as it behaves like a loudspeaker.
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// Basically, we want the PWM heating switched at 30Hz (or so) which is a well ballanced
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// frequency for both power supply units (i.e. both PSUs are reasonably silent).
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// The only trouble is the rising or falling edge of bed heating - that creates an audible click.
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// This audible click may be suppressed by making the rising or falling edge NOT sharp.
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// Of course, making non-sharp edges in digital technology is not easy, but there is a solution.
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// It is possible to do a fast PWM sequence with duty starting from 0 to 255.
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// Doing this at higher frequency than the bed "loudspeaker" can handle makes the click barely audible.
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// Technically:
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// timer0 is set to fast PWM mode at 62.5kHz (timer0 is linked to the bed heating pin) (zero prescaler)
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// To keep the bed switching at 30Hz - we don't want the PWM running at 62kHz all the time
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// since it would burn the heatbed's MOSFET:
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// 16MHz/256 levels of PWM duty gives us 62.5kHz
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// 62.5kHz/256 gives ~244Hz, that is still too fast - 244/8 gives ~30Hz, that's what we need
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// So the automaton runs atop of inner 8 (or 16) cycles.
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// The finite automaton is running in the ISR(TIMER0_OVF_vect)
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///! Definition off finite automaton states
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enum class States : uint8_t {
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ZERO = 0,
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RISE = 1,
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ONE = 2,
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FALL = 3
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};
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///! State table for the inner part of the finite automaton
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///! Basically it specifies what shall happen if the outer automaton is requesting setting the heat pin to 0 (OFF) or 1 (ON)
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///! ZERO: steady 0 (OFF), no change for the whole period
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///! RISE: 8 (16) fast PWM cycles with increasing duty up to steady ON
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///! ONE: steady 1 (ON), no change for the whole period
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///! FALL: 8 (16) fast PWM cycles with decreasing duty down to steady OFF
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///! @@TODO move it into progmem
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static States stateTable[4*2] = {
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// off on
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States::ZERO, States::RISE, // ZERO
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States::FALL, States::ONE, // RISE
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States::FALL, States::ONE, // ONE
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States::ZERO, States::RISE // FALL
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};
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///! Inner states of the finite automaton
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static States state = States::ZERO;
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///! Inner and outer PWM counters
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static uint8_t outer = 0;
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static uint8_t inner = 0;
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static uint8_t pwm = 0;
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///! the slow PWM duty for the next 30Hz cycle
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///! Set in the whole firmware at various places
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extern unsigned char soft_pwm_bed;
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/// Fine tuning of automaton cycles
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#if 1
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static const uint8_t innerMax = 16;
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static const uint8_t innerShift = 4;
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#else
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static const uint8_t innerMax = 8;
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static const uint8_t innerShift = 5;
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#endif
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ISR(TIMER0_OVF_vect) // timer compare interrupt service routine
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{
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if( inner ){
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switch(state){
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case States::ZERO:
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OCR0B = 255;
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// Commenting the following code saves 6B, but it is left here for reference
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// It is not necessary to set it all over again, because we can only get into the ZERO state from the FALL state (which sets this register)
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// TCCR0A |= (1 << COM0B1) | (1 << COM0B0);
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break;
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case States::RISE:
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OCR0B = (innerMax - inner) << innerShift;
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// TCCR0A |= (1 << COM0B1); // this bit is always 1
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TCCR0A &= ~(1 << COM0B0);
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break;
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case States::ONE:
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OCR0B = 255;
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// again - may be skipped, because we get into the ONE state only from RISE (which sets this register)
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// TCCR0A |= (1 << COM0B1);
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TCCR0A &= ~(1 << COM0B0);
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break;
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case States::FALL:
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OCR0B = (innerMax - inner) << innerShift; // this is the same as in RISE, because now we are setting the zero part of duty due to inverting mode
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// must switch to inverting mode already here, because it takes a whole PWM cycle and it would make a "1" at the end of this pwm cycle
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TCCR0A |= /*(1 << COM0B1) |*/ (1 << COM0B0);
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break;
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}
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--inner;
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} else {
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if( ! outer ){ // at the end of 30Hz PWM period
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// synchro is not needed (almost), soft_pwm_bed is just 1 byte, 1-byte write instruction is atomic
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pwm = soft_pwm_bed << 1;
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}
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if( pwm > outer || pwm >= 254 ){
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// soft_pwm_bed has a range of 0-127, that why a <<1 is done here. That also means that we may get only up to 254 which we want to be full-time 1 (ON)
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state = stateTable[ uint8_t(state) * 2 + 1 ];
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} else {
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// switch OFF
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state = stateTable[ uint8_t(state) * 2 + 0 ];
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}
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++outer;
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inner = innerMax;
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}
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}
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@ -4,7 +4,7 @@
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#define FIRMWARE_SYSTEM_TIMER_H_
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#include "Arduino.h"
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//#define SYSTEM_TIMER_2
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#define SYSTEM_TIMER_2
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#ifdef SYSTEM_TIMER_2
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#include "timer02.h"
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@ -13,12 +13,15 @@
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#define _delay delay2
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#define _tone tone2
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#define _noTone noTone2
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#define timer02_set_pwm0(pwm0)
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#else //SYSTEM_TIMER_2
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#define _millis millis
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#define _micros micros
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#define _delay delay
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#define _tone tone
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#define _noTone noTone
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#define _tone(x, y) /*tone*/
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#define _noTone(x) /*noTone*/
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#define timer02_set_pwm0(pwm0)
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#endif //SYSTEM_TIMER_2
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@ -44,8 +44,6 @@
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#include "Timer.h"
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#include "Configuration_prusa.h"
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//===========================================================================
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//=============================public variables============================
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//===========================================================================
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@ -1130,18 +1128,9 @@ void tp_init()
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adc_init();
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#ifdef SYSTEM_TIMER_2
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timer02_init();
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timer0_init();
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OCR2B = 128;
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TIMSK2 |= (1<<OCIE2B);
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#else //SYSTEM_TIMER_2
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// Use timer0 for temperature measurement
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// Interleave temperature interrupt with millies interrupt
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OCR0B = 128;
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TIMSK0 |= (1<<OCIE0B);
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#endif //SYSTEM_TIMER_2
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// Wait for temperature measurement to settle
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_delay(250);
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@ -1472,8 +1461,8 @@ void disable_heater()
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target_temperature_bed=0;
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soft_pwm_bed=0;
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timer02_set_pwm0(soft_pwm_bed << 1);
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#if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
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WRITE(HEATER_BED_PIN,LOW);
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#if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
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//WRITE(HEATER_BED_PIN,LOW);
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#endif
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#endif
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}
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@ -1544,7 +1533,7 @@ void min_temp_error(uint8_t e) {
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void bed_max_temp_error(void) {
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#if HEATER_BED_PIN > -1
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WRITE(HEATER_BED_PIN, 0);
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//WRITE(HEATER_BED_PIN, 0);
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#endif
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if(IsStopped() == false) {
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SERIAL_ERROR_START;
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@ -1563,7 +1552,7 @@ void bed_min_temp_error(void) {
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#endif
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//if (current_temperature_ambient < MINTEMP_MINAMBIENT) return;
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#if HEATER_BED_PIN > -1
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WRITE(HEATER_BED_PIN, 0);
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//WRITE(HEATER_BED_PIN, 0);
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#endif
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static const char err[] PROGMEM = "Err: MINTEMP BED";
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if(IsStopped() == false) {
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@ -1660,7 +1649,6 @@ void adc_ready(void) //callback from adc when sampling finished
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} // extern "C"
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// Timer2 (originaly timer0) is shared with millies
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#ifdef SYSTEM_TIMER_2
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ISR(TIMER2_COMPB_vect)
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@ -1676,8 +1664,8 @@ ISR(TIMER0_COMPB_vect)
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if (!temp_meas_ready) adc_cycle();
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lcd_buttons_update();
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static unsigned char pwm_count = (1 << SOFT_PWM_SCALE);
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static unsigned char soft_pwm_0;
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static uint8_t pwm_count = (1 << SOFT_PWM_SCALE);
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static uint8_t soft_pwm_0;
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#ifdef SLOW_PWM_HEATERS
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static unsigned char slow_pwm_count = 0;
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static unsigned char state_heater_0 = 0;
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@ -1698,7 +1686,7 @@ ISR(TIMER0_COMPB_vect)
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#endif
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#endif
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#if HEATER_BED_PIN > -1
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static unsigned char soft_pwm_b;
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// @@DR static unsigned char soft_pwm_b;
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#ifdef SLOW_PWM_HEATERS
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static unsigned char state_heater_b = 0;
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static unsigned char state_timer_heater_b = 0;
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@ -1733,14 +1721,25 @@ ISR(TIMER0_COMPB_vect)
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#endif
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}
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#if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
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#if 0 // @@DR vypnuto pro hw pwm bedu
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// tuhle prasarnu bude potreba poustet ve stanovenych intervalech, jinak nemam moc sanci zareagovat
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// teoreticky by se tato cast uz vubec nemusela poustet
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if ((pwm_count & ((1 << HEATER_BED_SOFT_PWM_BITS) - 1)) == 0)
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{
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soft_pwm_b = soft_pwm_bed >> (7 - HEATER_BED_SOFT_PWM_BITS);
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#ifndef SYSTEM_TIMER_2
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if(soft_pwm_b > 0) WRITE(HEATER_BED_PIN,1); else WRITE(HEATER_BED_PIN,0);
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#endif //SYSTEM_TIMER_2
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# ifndef SYSTEM_TIMER_2
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// tady budu krokovat pomalou frekvenci na automatu - tohle je rizeni spinani a rozepinani
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// jako ridici frekvenci mam 2khz, jako vystupni frekvenci mam 30hz
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// 2kHz jsou ovsem ve slysitelnem pasmu, mozna bude potreba jit s frekvenci nahoru (a tomu taky prizpusobit ostatni veci)
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// Teoreticky bych mohl stahnout OCR0B citac na 6, cimz bych se dostal nekam ke 40khz a tady potom honit PWM rychleji nebo i pomaleji
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// to nicemu nevadi. Soft PWM scale by se 20x zvetsilo (no dobre, 16x), cimz by se to posunulo k puvodnimu 30Hz PWM
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//if(soft_pwm_b > 0) WRITE(HEATER_BED_PIN,1); else WRITE(HEATER_BED_PIN,0);
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# endif //SYSTEM_TIMER_2
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}
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#endif
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#endif
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#ifdef FAN_SOFT_PWM
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if ((pwm_count & ((1 << FAN_SOFT_PWM_BITS) - 1)) == 0)
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{
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@ -1762,8 +1761,14 @@ ISR(TIMER0_COMPB_vect)
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#if EXTRUDERS > 2
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if(soft_pwm_2 < pwm_count) WRITE(HEATER_2_PIN,0);
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#endif
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#if 0 // @@DR
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#if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
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if (soft_pwm_b < (pwm_count & ((1 << HEATER_BED_SOFT_PWM_BITS) - 1))) WRITE(HEATER_BED_PIN,0);
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if (soft_pwm_b < (pwm_count & ((1 << HEATER_BED_SOFT_PWM_BITS) - 1))){
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//WRITE(HEATER_BED_PIN,0);
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}
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//WRITE(HEATER_BED_PIN, pwm_count & 1 );
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#endif
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#endif
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#ifdef FAN_SOFT_PWM
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if (soft_pwm_fan < (pwm_count & ((1 << FAN_SOFT_PWM_BITS) - 1))) WRITE(FAN_PIN,0);
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@ -9,48 +9,27 @@
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include "Arduino.h"
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#include "io_atmega2560.h"
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#define BEEPER 84
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uint8_t timer02_pwm0 = 0;
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void timer02_set_pwm0(uint8_t pwm0)
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{
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if (timer02_pwm0 == pwm0) return;
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if (pwm0)
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{
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TCCR0A |= (2 << COM0B0);
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OCR0B = pwm0 - 1;
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}
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else
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{
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TCCR0A &= ~(2 << COM0B0);
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OCR0B = 0;
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}
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timer02_pwm0 = pwm0;
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}
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void timer02_init(void)
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void timer0_init(void)
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{
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//save sreg
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uint8_t _sreg = SREG;
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//disable interrupts for sure
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cli();
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//mask timer0 interrupts - disable all
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TIMSK0 &= ~(1<<TOIE0);
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TIMSK0 &= ~(1<<OCIE0A);
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TIMSK0 &= ~(1<<OCIE0B);
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//setup timer0
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TCCR0A = 0x00; //COM_A-B=00, WGM_0-1=00
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TCCR0B = (1 << CS00); //WGM_2=0, CS_0-2=011
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//switch timer0 to fast pwm mode
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TCCR0A |= (3 << WGM00); //WGM_0-1=11
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//set OCR0B register to zero
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OCR0B = 0;
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//disable OCR0B output (will be enabled in timer02_set_pwm0)
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TCCR0A &= ~(2 << COM0B0);
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TCNT0 = 0;
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// Fast PWM duty (0-255).
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// Due to invert mode (following rows) the duty is set to 255, which means zero all the time (bed not heating)
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OCR0B = 255;
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// Set fast PWM mode and inverting mode.
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TCCR0A = (1 << WGM01) | (1 << WGM00) | (1 << COM0B1) | (1 << COM0B0);
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TCCR0B = (1 << CS00); // no clock prescaling
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TIMSK0 |= (1 << TOIE0); // enable timer overflow interrupt
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// Everything, that used to be on timer0 was moved to timer2 (delay, beeping, millis etc.)
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//setup timer2
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TCCR2A = 0x00; //COM_A-B=00, WGM_0-1=00
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TCCR2B = (4 << CS20); //WGM_2=0, CS_0-2=011
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@ -66,11 +45,9 @@ void timer02_init(void)
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}
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//following code is OVF handler for timer 2
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//it is copy-paste from wiring.c and modified for timer2
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//variables timer0_overflow_count and timer0_millis are declared in wiring.c
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// The following code is OVF handler for timer 2
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// it was copy-pasted from wiring.c and modified for timer2
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// variables timer0_overflow_count and timer0_millis are declared in wiring.c
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// the prescaler is set so that timer0 ticks every 64 clock cycles, and the
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// the overflow handler is called every 256 ticks.
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@ -85,9 +62,6 @@ void timer02_init(void)
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#define FRACT_INC ((MICROSECONDS_PER_TIMER0_OVERFLOW % 1000) >> 3)
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#define FRACT_MAX (1000 >> 3)
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//extern volatile unsigned long timer0_overflow_count;
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//extern volatile unsigned long timer0_millis;
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//unsigned char timer0_fract = 0;
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volatile unsigned long timer2_overflow_count;
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volatile unsigned long timer2_millis;
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unsigned char timer2_fract = 0;
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@ -11,24 +11,25 @@
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extern "C" {
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#endif //defined(__cplusplus)
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///! Initializes TIMER0 for fast PWM mode-driven bed heating
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extern void timer0_init(void);
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extern uint8_t timer02_pwm0;
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extern void timer02_set_pwm0(uint8_t pwm0);
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extern void timer02_init(void);
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///! Reimplemented original millis() using timer2
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extern unsigned long millis2(void);
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///! Reimplemented original micros() using timer2
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extern unsigned long micros2(void);
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///! Reimplemented original delay() using timer2
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extern void delay2(unsigned long ms);
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///! Reimplemented original tone() using timer2
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///! Does not perform any PWM tone generation, it just sets the beeper pin to 1
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extern void tone2(uint8_t _pin, unsigned int frequency/*, unsigned long duration*/);
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///! Turn off beeping - set beeper pin to 0
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extern void noTone2(uint8_t _pin);
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#if defined(__cplusplus)
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}
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#endif //defined(__cplusplus)
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