Arduino due pwm pins and attribute

Hello,

I'm trying to use PWM Output on my Arduino Due. I realised something strange in my eyes: It says, that there are 12 pins to use PWM on (pin 2-13). But on my board only pin6-9 are working.
While digging in some .h and .c/.cpp files to understand the functions (because I wanted to do some alterations) I found the file variants.cpp where it says, that only pin6-9 get the attribute "pwm":

// 2
  { PIOB, PIO_PB25B_TIOA0,   ID_PIOB, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_TIMER), NO_ADC, NO_ADC, NOT_ON_PWM,  TC0_CHA0     }, // TIOA0
  { PIOC, PIO_PC28B_TIOA7,   ID_PIOC, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_TIMER), NO_ADC, NO_ADC, NOT_ON_PWM,  TC2_CHA7     }, // TIOA7
  { PIOC, PIO_PC26B_TIOB6,   ID_PIOC, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_TIMER), NO_ADC, NO_ADC, NOT_ON_PWM,  TC2_CHB6     }, // TIOB6

  // 5
  { PIOC, PIO_PC25B_TIOA6,   ID_PIOC, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_TIMER), NO_ADC, NO_ADC, NOT_ON_PWM,  TC2_CHA6     }, // TIOA6
  { PIOC, PIO_PC24B_PWML7,   ID_PIOC, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM),   NO_ADC, NO_ADC, PWM_CH7,     NOT_ON_TIMER }, // PWML7
  { PIOC, PIO_PC23B_PWML6,   ID_PIOC, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM),   NO_ADC, NO_ADC, PWM_CH6,     NOT_ON_TIMER }, // PWML6
  { PIOC, PIO_PC22B_PWML5,   ID_PIOC, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM),   NO_ADC, NO_ADC, PWM_CH5,     NOT_ON_TIMER }, // PWML5
  { PIOC, PIO_PC21B_PWML4,   ID_PIOC, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM),   NO_ADC, NO_ADC, PWM_CH4,     NOT_ON_TIMER }, // PWML4
  // 10
  { PIOC, PIO_PC29B_TIOB7,   ID_PIOC, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_TIMER), NO_ADC, NO_ADC, NOT_ON_PWM,  TC2_CHB7     }, // TIOB7
  { PIOD, PIO_PD7B_TIOA8,    ID_PIOD, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_TIMER), NO_ADC, NO_ADC, NOT_ON_PWM,  TC2_CHA8     }, // TIOA8
  { PIOD, PIO_PD8B_TIOB8,    ID_PIOD, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_TIMER), NO_ADC, NO_ADC, NOT_ON_PWM,  TC2_CHB8     }, // TIOB8

  // 13 - AMBER LED
  { PIOB, PIO_PB27B_TIOB0,   ID_PIOB, PIO_PERIPH_B, PIO_DEFAULT, (PIN_ATTR_DIGITAL|PIN_ATTR_TIMER), NO_ADC, NO_ADC, NOT_ON_PWM,  TC0_CHB0     }, // TIOB0

So only four predefined Pins can actually be used as PWM pin, if you just use the arduino framework as is. Did I miss any documentation, where this fact is written?

Can anyone enlighten the background to this file variant.cpp.

I hope this question is right in this forum, otherwise perhaps you can move it. I did not find a better location.

Thanks a lot for helping me understand Arduino.

If you look at the Graynomad pinout diagram, you will see pins quoted: TIOAx or TIOBx (For Timer Counter peripheral) or PWMHx or PWMLx (for the PWM peripheral). You can output a PWM pulse from all of these pins, e.g. by using PWM_lib or TC_lib from antodom.

lh89:
on my board only pin6-9 are working.

Please post your sketch. I can tell you that with my Due, I can use analogWrite() on pins 2-13 as promised by the documentation.

lh89:
I found the file variants.cpp where it says, that only pin6-9 get the attribute "pwm":

PIN_ATTR_PWM, yes, but look at the code for analogWrite():

You can see that function can be used to produce a PWM signal on the pins defined with the PIN_ATTR_TIMER attribute as well as the PIN_ATTR_PWM attribute in variant.cpp.