LEDC Module

Since Origin / Contributor Maintainer Source
2017-07-05 Lars Stenberg Lars Stenberg ledc.c

This module provides access to the LEDC PWM driver.

LEDC Overview

The LED control module is primarily designed to control the intensity of LEDs, although it can be used to generate PWM signals for other purposes as well. It has 16 channels which can generate independent waveforms that can be used to drive e.g. RGB LED devices. For maximum flexibility, the high-speed as well as the low-speed channels can be driven from one of four high-speed/low-speed timers. The PWM controller also has the ability to automatically increase or decrease the duty cycle gradually, allowing for fades without any processor interference.

ledc.newChannel()

Configures a PIN to be controlled by the LEDC system.

Syntax

myChannel = ledc.newChannel({
  gpio=x,
  bits=ledc.TIMER_10_BIT || ledc.TIMER_11_BIT || ledc.TIMER_12_BIT || ledc.TIMER_13_BIT || ledc.TIMER_14_BIT || ledc.TIMER_15_BIT,
  mode=ledc.HIGH_SPEED || ledc.LOW_SPEED,
  timer=ledc.TIMER_0 || ledc.TIMER_1 || ledc.TIMER_2 || ledc.TIMER_3,
  channel=ledc.CHANNEL_0 || ledc.CHANNEL_1 || ledc.CHANNEL_2 || ledc.CHANNEL_3 || ledc.CHANNEL_4 || ledc.CHANNEL_5 || ledc.CHANNEL_6 || ledc.CHANNEL_7,
  frequency=x,
  duty=x
});

Parameters

List of configuration tables:

  • gpio one or more (given as list) pins, see GPIO Overview
  • bits Channel duty depth. Defaults to ledc.TIMER_13_BIT. Otherwise one of
    • ledc.TIMER_10_BIT
    • ...
    • ledc.TIMER_15_BIT
  • mode High-speed mode or low-speed mode
    • ledc.HIGH_SPEED
    • ledc.LOW_SPEED
  • timer The timer source of channel
    • ledc.TIMER_0
    • ...
    • ledc.TIMER_3
  • channel The timer source of channel
    • ledc.CHANNEL_0
    • ...
    • ledc.CHANNEL_7
  • frequency Timer frequency(Hz)
  • duty Channel duty, the duty range is [0, (2**bit_num) - 1]. Example: if ledc.TIMER_13_BIT is used maximum value is 4096 x 2 -1 = 8091

Returns

channel ledc.channel

Example

myChannel = ledc.newChannel({
  gpio=19,
  bits=ledc.TIMER_13_BIT,
  mode=ledc.HIGH_SPEED,
  timer=ledc.TIMER_0,
  channel=ledc.CHANNEL_0,
  frequency=1000,
  duty=4096
});

LEDC channel module

All interactions with the LEDC subsystem is done on the channel object created using the newChannel method.

ledc.channel:stop()

Disable LEDC output, and set idle level.

Syntax

channel:stop(idleLevel)

Parameters

  • idleLevel Set output idle level after LEDC stops.
    • ledc.IDLE_LOW
    • ledc.IDLE_HIGH

Returns

nil

Example

channel:stop(ledc.IDLE_LOW)

ledc.channel:setfreq()

Set channel frequency (Hz)

Syntax

channel:setfreq(frequency)

Parameters

  • frequency What frequency should be set

Returns

nil

Example

channel:setfreq(2000)

ledc.channel:getfreq()

Get channel frequency (Hz)

Syntax

channel:getfreq()

Parameters

None

Returns

  • 0 error
  • Others current LEDC frequency

Example

channel:getfreq()

ledc.channel:setduty()

Set channel duty

Syntax

channel:setdutyduty)

Parameters

  • duty What duty should be set

Returns

nil

Example

channel:setduty(4096)

ledc.channel:getduty()

Get channel duty

Syntax

channel:getduty()

Parameters

None

Returns

  • (-1) parameter error
  • Others current LEDC duty

Example

channel:getduty()

ledc.channel:reset()

Resets the timer

Syntax

channel:reset()

Parameters

None

Returns

nil

Example

channel:reset();

ledc.channel:pause()

Pauses the timer

Syntax

channel:pause()

Parameters

None

Returns

nil

Example

channel:pause();

ledc.channel:resume()

Resumes a paused timer

Syntax

channel:resume()

Parameters

None

Returns

nil

Example

channel:resume()

ledc.channel:fadewithtime()

Set LEDC fade function, with a limited time.

Syntax

channel:fadewithtime(targetDuty, maxFadeTime[, wait])

Parameters

  • targetDuty Target duty of fading.
  • maxFadeTime The maximum time of the fading ( ms ).
  • wait Whether to block until fading done.
    • ledc.FADE_NO_WAIT (default)
    • ledc.FADE_WAIT_DONE

Returns

nil

Example

channel:fadewithtime(4096, 1000);

ledc.channel:fadewithstep()

Set LEDC fade function, with step.

Syntax

channel:fadewithstep(targetDuty, scale, cycleNum[, wait])

Parameters

  • targetDuty Target duty of fading.
  • scale Controls the increase or decrease step scale.
  • cycleNum Increase or decrease the duty every cycle_num cycles
  • wait Whether to block until fading done.
    • ledc.FADE_NO_WAIT (default)
    • ledc.FADE_WAIT_DONE

Returns

nil

Example

channel:fadewithstep(1000, 10, 10);

ledc.channel:fade()

Set LEDC fade function.

Syntax

channel:fadewithstep(duty, direction, scale, cycleNum, stepNum [, wait])

Parameters

  • duty Set the start of the gradient duty.
  • direction Set the direction of the gradient.
    • ledc.FADE_DECREASE
    • ledc.FADE_INCREASE
  • scale Set gradient change amplitude.
  • cycleNum Set how many LEDC tick each time the gradient lasts.
  • stepNum Set the number of the gradient.
  • wait Whether to block until fading done.
    • ledc.FADE_NO_WAIT (default)
    • ledc.FADE_WAIT_DONE

Returns

nil

Example

channel:fade(0, ledc.FADE_INCREASE, 100, 100, 1000);