ChibiOS Free Embedded RTOS

Posted: **Thu Nov 20, 2014 8:19 pm**

So the setting should be like:

static PWMConfig pwmcfg = {
  10000, /* 10Khz PWM clock frequency */
  10,
  NULL,  /* No callback */
  /* Only channel 1 enabled */
  {
    {PWM_OUTPUT_ACTIVE_HIGH | PWM_COMPLEMENTARY_OUTPUT_ACTIVE_HIGH, NULL},
    {PWM_OUTPUT_DISABLED, NULL},
    {PWM_OUTPUT_DISABLED, NULL},
    {PWM_OUTPUT_DISABLED, NULL},
  },
  0,
  0,
#if STM32_PWM_USE_ADVANCED
  0
#endif
};

Code: Select all

 /* Enables PWM output (of TIM1, channel 1) on LED connected to PA8 */
  palSetPadMode(GPIOA, 8, PAL_MODE_STM32_ALTERNATE_PUSHPULL);

  /* Enables PWM output (of TIM1, channel 1N) on LED connected to PB13 */
  palSetPadMode(GPIOB, 13, PAL_MODE_STM32_ALTERNATE_PUSHPULL);

  pwmStart(&PWMD1, &pwmcfg);
  pwmEnableChannel(&PWMD1, 0, 100);

???

Posted: **Thu Nov 20, 2014 8:26 pm**

Note that you set the period to 10 this means that you have 11 integer duty cycle settings for your PWM: 0...10. This means that you cannot set the duty cycle to 100, 10 is the maximum.

Both the period and the duty cycle are expressed as number of clock cycles.

Giovanni

Posted: **Wed Nov 26, 2014 12:29 pm**

Hi Giovani,

Now it is clear. I'm wondering if it is possible to get 500kHz signal. Can I set PWMConfig like this:

Code: Select all

static PWMConfig pwmcfg = {
  5000000, /* 5MHz PWM clock frequency */
  10,
  NULL,  /* No callback */
  /* Only channel 1 enabled */
  {
    {PWM_OUTPUT_ACTIVE_HIGH | PWM_COMPLEMENTARY_OUTPUT_ACTIVE_HIGH, NULL},
    {PWM_OUTPUT_DISABLED, NULL},
    {PWM_OUTPUT_DISABLED, NULL},
    {PWM_OUTPUT_DISABLED, NULL},
  },
  0,
  0,
#if STM32_PWM_USE_ADVANCED
  0
#endif
};

Code: Select all

/* Enables PWM output (of TIM1, channel 1) on LED connected to PA8 */
  palSetPadMode(GPIOA, 8, PAL_MODE_STM32_ALTERNATE_PUSHPULL);

  /* Enables PWM output (of TIM1, channel 1N) on LED connected to PB13 */
  palSetPadMode(GPIOB, 13, PAL_MODE_STM32_ALTERNATE_PUSHPULL);

  pwmStart(&PWMD1, &pwmcfg);
  pwmEnableChannel(&PWMD1, 0, 5);

Posted: **Wed Nov 26, 2014 1:48 pm**

The clock frequency must be something you can obtain from the timer clock using an integer divider, so no.

If you try that an assertion will block you in pwmStart().

Giovanni

Posted: **Wed Nov 26, 2014 2:13 pm**

So maybe you have some idea how to obtain that kind of PWM frequency?

Posted: **Wed Nov 26, 2014 2:17 pm**

Clocking the device to a frequency that can be divided by 5000000.

Giovanni

ChibiOS Free Embedded RTOS

STM32F100 on STM32VL Discovery - PWM complementary

Re: STM32F100 on STM32VL Discovery - PWM complementary

Re: STM32F100 on STM32VL Discovery - PWM complementary

Re: STM32F100 on STM32VL Discovery - PWM complementary

Re: STM32F100 on STM32VL Discovery - PWM complementary

Re: STM32F100 on STM32VL Discovery - PWM complementary

Re: STM32F100 on STM32VL Discovery - PWM complementary