ChibiOS Free Embedded RTOS

Posted: **Wed Mar 02, 2016 11:33 am**

Hello,

I have a small module that uses two channels on the PWM5.
I would like to be able to modify the duty cycle of one of these two channels.

My problem is that when i modify the duty cycle of one channel, the second channel is resetted.

To modify the duty cycle, i use the function pwmEnableChannel.
I think it is the culprit that disable the second PWM.

Is there another function under Chibios to change the duty cycle without interfering with another channel ?
Or do i have to play with the TIM5_CCRx registers ?

Thank you in advance.

Stephane

Posted: **Wed Mar 02, 2016 11:46 am**

Hi,

pwmEnableChannel() only touches the CCR register, this should not happen but it happens because a stupid bug in this code...

I imagine you are using an STM32F3, correct?

Code: Select all

void pwm_lld_enable_channel(PWMDriver *pwmp,
                            pwmchannel_t channel,
                            pwmcnt_t width) {

  /* Changing channel duty cycle on the fly.*/
#if STM32_TIM_MAX_CHANNELS <= 4
  pwmp->tim->CCR[channel] = width;
#else
  if (channel <= 4)
    pwmp->tim->CCR[channel] = width;
  else
    pwmp->tim->CCXR[channel - 4] = width;
#endif
}

Opened a ticket: https://sourceforge.net/p/chibios/bugs/722/
Will be fixed in 16.1.4 (next weekend).

Giovanni

Posted: **Wed Mar 02, 2016 1:27 pm**

Hi,

You are very impressive: very fast answer and correct guess.

(Sorry, i forgotten to specify that i am using a STM32F373)

Thanks a lot for your help !

Stéphane

Posted: **Thu Mar 03, 2016 4:29 pm**

Hello again,

I have to confess that i found a misplaced pwmStart() on my code...

On my case, with Chibios 3.0.0, the pwmEnableChannel() routine seems to work correctly.

With best regards,

Stéphane

ChibiOS Free Embedded RTOS

Change PWM duty cycle

Change PWM duty cycle

Re: Change PWM duty cycle

Re: Change PWM duty cycle

Re: Change PWM duty cycle