eLua platform interface - PWM

Overview

This part of the platform interface groups functions related to the PWM channel(s) of the MCU.

Data structures, constants and types

// PWM operations
enum
{
  PLATFORM_PWM_OP_START,
  PLATFORM_PWM_OP_STOP,
  PLATFORM_PWM_OP_SET_CLOCK,
  PLATFORM_PWM_OP_GET_CLOCK
}

This enum lists all the operations that can be executed on a given PWM channel.

Functions

platform_pwm_exists platform_pwm_setup platform_pwm_start platform_pwm_stop platform_pwm_set_clock platform_pwm_get_clock

int platform_pwm_exists( unsigned id );

Checks if the platform has the PWM channel specified as argument. Implemented in src/common.c, it uses the NUM_PWM macro that must be defined in the platform's platform_conf.h file (see here for details). For example:

#define NUM_PWM   4      // The platform has 4 PWM channels

Arguments: id - PWM channel ID

Returns: 1 if the specified PWM channel exists, 0 otherwise

u32 platform_pwm_setup( unsigned id, u32 frequency, unsigned duty );

Sets up a PWM channel

Arguments:

  • id - PWM channel ID
  • frequency - PWM channel frequency (in hertz)
  • duty - PWM channel duty cycle, specified as percent (from 0 to 100). Note that some platform don't allow the full 0-100 duty cycle

Returns: The actual frequency set on the PWM channel, which might differ from the frequency parameter, depeding on the hardware

u32 platform_pwm_start( unsigned id );

Starts PWM generation on the specified channel

Arguments: id - PWM channel ID

Returns: nothing.

u32 platform_pwm_stop( unsigned id );

Stops PWM generation on the specified channel

Arguments: id - PWM channel ID

Returns: nothing.

u32 platform_pwm_set_clock( unsigned id, u32 clock );

Sets the base clock of the specified PWM channel (which will be used to generate the frequencies requested by platform_pwm_setup) to data hertz.

Arguments:

  • id - PWM channel ID
  • clock - the desired frequency of the base clock.

Returns: The actual value of the base clock, which might be different from data depending on the hardware

u32 platform_pwm_get_clock( unsigned id );

Gets the base clock of the specified PWM channel

Arguments:

  • id - PWM channel ID
  • clock - the desired frequency of the base clock.

Returns: the value of the base clock