Linear Advance extrusion breaks Fan PWM on PIN 4

[Kaibob2]

When #define LIN_ADVANCE in Configuration_adv.h is uncommented the fan on PIN 4 loses the PWM capability.

In other words: M106 S255 switches the fan on, M106 S254 - M106 S0 switches it off. #define FAN_KICKSTART_TIME 100 still works as always.

When commenting #define LIN_ADVANCE the fan PWM works perfect again.

PS: The same happens when uncommenting #define ADVANCE. But this was only for testing as i read that it isn't working properly. The prints with LIN_ADVANCE enabled looked really promising yesterday, but PLA without a PWM fan isn't an option.

[Blue-Marlin]

There is no simple way to change that. Both use timer 0. Better take an other pin. You could try to use #define FAN_SOFT_PWM

[thinkyhead]

@Blue-Marlin Looks like something we might need to account-for. Perhaps in Conditionals_post.h…

#if (HAS_FAN0 || HAS_FAN1) && ENABLED(LIN_ADVANCE)
  #define FAN_SOFT_PWM
#endif

[Blue-Marlin]

At first lets wait for @Kaibob2 s answer - if FAN_SOFT_PWM helps.

HAS_FAN0 or HAS_FAN1 is wrong. It depends on the pin number and the type of the processor, and if analogWrite() is used to get a PWM.

I looked it up for the ATmega2560-Arduino Mega in pins_arduino.h. There you can find an array digital_pin_to_timer_PGM[]. Therein you can find the timers related to the pin numbers.

const uint8_t PROGMEM digital_pin_to_timer_PGM[] = {
    // TIMERS       
    // -------------------------------------------      
    NOT_ON_TIMER    , // PE 0 ** 0 ** USART0_RX 
    NOT_ON_TIMER    , // PE 1 ** 1 ** USART0_TX 
    TIMER3B , // PE 4 ** 2 ** PWM2  
    TIMER3C , // PE 5 ** 3 ** PWM3  
    TIMER0B , // PG 5 ** 4 ** PWM4  
    TIMER3A , // PE 3 ** 5 ** PWM5  
    TIMER4A , // PH 3 ** 6 ** PWM6  
    TIMER4B , // PH 4 ** 7 ** PWM7  
    TIMER4C , // PH 5 ** 8 ** PWM8  
    TIMER2B , // PH 6 ** 9 ** PWM9  
    TIMER2A , // PB 4 ** 10 ** PWM10    
    TIMER1A , // PB 5 ** 11 ** PWM11    
    TIMER1B , // PB 6 ** 12 ** PWM12    
    TIMER0A , // PB 7 ** 13 ** PWM13    
    NOT_ON_TIMER    , // PJ 1 ** 14 ** USART3_TX    
    NOT_ON_TIMER    , // PJ 0 ** 15 ** USART3_RX    
    NOT_ON_TIMER    , // PH 1 ** 16 ** USART2_TX    
    NOT_ON_TIMER    , // PH 0 ** 17 ** USART2_RX    
    NOT_ON_TIMER    , // PD 3 ** 18 ** USART1_TX    
...

    TIMER0B , // PG 5 ** 4 ** PWM4  
    TIMER0A , // PB 7 ** 13 ** PWM13    

are relevant for timer 0.

But also

    TIMER1A , // PB 5 ** 11 ** PWM11    
    TIMER1B , // PB 6 ** 12 ** PWM12    

can not be used for hardware PWM because of the stepper interrupt at timer 1.

For other processors/boards the register names and pin numbers may be different.

[Kaibob2]

Enabling FAN_SOFT_PWM works. Does this have any negative impact on something else like the extruder heaters, bed or MOSFET heating?

[Kaibob2]

I built an 4 channel extension PCB for the servo port which uses PIN 4,5,6 and 11. PIN 4: Filament cooling fan (controlled via S3D Gcode M106) _works_ PIN 5: Controller Fan (controlled via Marlin CONTROLLERFAN_PIN 5 / CONTROLLERFAN_SPEED 200) _works_ PIN 6: Extruder cooling fans (controlled via Marlin EXTRUDER_0_AUTO_FAN_PIN 6 / EXTRUDER_AUTO_FAN_SPEED 200) _works_ PIN 11: LEDs for building room (Manual control via M42 P11 Sxxx ) No PWM. Only on and off

Here is the question: PIN 11 is not PWMable. Why?

[Blue-Marlin]

To cite myself:

But also

    TIMER1A , // PB 5 ** 11 ** PWM11    
    TIMER1B , // PB 6 ** 12 ** PWM12    

can not be used for hardware PWM because of the stepper interrupt at timer 1.

[Blue-Marlin]

// Use software PWM to drive the fan, as for the heaters. This uses a very low frequency // which is not as annoying as with the hardware PWM. On the other hand, if this frequency // is too low, you should also increment SOFT_PWM_SCALE. //#define FAN_SOFT_PWM

// Incrementing this by 1 will double the software PWM frequency, // affecting heaters, and the fan if FAN_SOFT_PWM is enabled. // However, control resolution will be halved for each increment; // at zero value, there are 128 effective control positions.

define SOFT_PWM_SCALE 0

I don't expect more negative effects.

[Kaibob2]

Sorry for that. In Germany we say (free translated) "The ones who can read have an advantage".

Does this mean, with "FAN_SOFT_PWM" enabled and adding "#define FAN1_PIN 11" in "pins_RAMPS.h", PWM on Pin 11 would work?

[Blue-Marlin]

Never tried it. But i expect it to work. In the time i write this, you could simply have made a test by your own.

[Kaibob2]

Sure, sorry to bug you with this.

[Kaibob2]

Enabling Soft PWM works.

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