PWM

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Data Types

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shared_mode

Determines the way in which libsoc handles exporting and unexporting PWMs in the Linux subsystem.

• LS_PWM_SHARED

  if the pwm is already exported then it will not unexport the pwm on free. If it is not exported, then it will unexport on free.

• LS_PWM_GREEDY

  will succeed if the pwm is already exported, but will always unexport the pwm on free.

• LS_PWM_WEAK

  will fail if pwm is already exported, will always unexport on free.

pwm_enabled

Used for setting and reading the enabled state of the PWM device

• ENABLED_ERROR

  Returned when the enabled state could not be read

• DISABLED

  PWM disabled mode, the pwm is not currently running

• ENABLED

  PWM enabled mode, the pwm is currently running

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pwm_polarity

Used for setting and reading the polarity of the PWM device

• POLARITY_ERROR

  Returned when the polarity could not be read

• NORMAL

  Polarity mode is normal

• INVERSED

  Polarity mode is inversed

Functions

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libsoc_pwm_request

pwm* libsoc_pwm_request(unsigned int pwm_chip, unsigned int pwm_num, enum shared_mode mode)

• unsigned int pwm_chip

  the pwm chip number which controls the pwm you wish to use

• unsigned int pwm_num

  the pwm number within your specified pwm chip

• shared_mode mode

  the mode in which libsoc handles the PWM file descriptor

Request a pwm by specifying its pwm chip number and the pwm number it is on that chip. Set shared_mode to handle how libsoc manages the file descriptor. Returns a malloced pwm struct which will need to be freed by libsoc_pwm_free when no longer needed.

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libsoc_pwm_free

int libsoc_pwm_free(pwm *pwm)

• pwm* pwm

  the previously requested pwm that you wish to release

Free the memory associated with a previously requested PWM device and close the file descriptors.

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libsoc_pwm_set_enabled

int libsoc_pwm_set_enabled(pwm *pwm, pwm_enabled enabled)

• pwm* pwm

  requested pwm that you wish to set enabled/disabled

• pwm_enabled enabled

  state you wish to set the pwm device to

Set the state of a PWM device, ENABLED to enable to the device, DISABLED to disable the device.

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libsoc_pwm_get_enabled

pwm_enabled libsoc_pwm_get_enabled(pwm *pwm)

• pwm* pwm

  requested pwm that you wish to get the state of

Get the current pwm_enabled state of a requested PWM device.

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libsoc_pwm_set_period

int libsoc_pwm_set_period(pwm *pwm, unsigned int period)

• pwm* pwm

  requested pwm that you wish to set the period of

• unsigned int period

  the total period of the pwm signal in nanoseconds

Set the period of a PWM device, the value is specified in nanoseconds and is the sum of the active and inactive time of the signal.

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libsoc_pwm_get_period

int libsoc_pwm_get_period(pwm *pwm)

• pwm* pwm

  requested pwm that you wish to get the period of

Get the currently set perioid of the PWM device in nanoseconds.

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libsoc_pwm_set_duty_cycle

int libsoc_pwm_set_duty_cycle(pwm *pwm, unsigned int duty)

• pwm* pwm

  requested pwm that you wish to set the duty cycle of

• unsigned int duty

  the duty cycle in nanoseconds

Set the duty cycle of the specified PWM device in nanoseconds. The duty cycle is the active time of the PWM signal and must be less than the period.

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libsoc_pwm_get_duty_cycle

int libsoc_pwm_get_duty_cycle(pwm *pwm)

• pwm* pwm

  requested pwm that you wish to get the duty cycle of

Get the currently set duty cycle of a requested PWM device in nanoseconds.

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libsoc_pwm_set_polarity

int libsoc_pwm_set_polarity(pwm *pwm, pwm_polarity polarity)

• pwm* pwm

  requested pwm that you wish to set the polarity of

• pwm_polarity polarity

  polarity you wish to set the pwm device to

Set the polarity of a PWM device, NORMAL will give you the default polarity, INVERSED will give you the inverse polarity of normal.

Polarity support is optional, ensure your PWM devices kernel driver is capable before relying on this support. The value -1 will be returned on failure to set the polarity.

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libsoc_pwm_get_polarity

pwm_polarity libsoc_pwm_get_polarity(pwm *pwm)

• pwm* pwm

  requested pwm that you wish to get the polarity of

Get the current pwm_polarity of a requested PWM device.

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