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Arduino/Wiring SoftPWM Library

What's New?

Version 0005:

• Fixed Arduino 1.0 mess.
• Added Polarity control.
• Up to 20 channels can be defined.

Download

• Temporary: http://rogue-code.googlecode.com/files/Wiring-Library-SoftPWM-V0005.zip
• (will update to GitHub releases)

Installation

TODO

Description

An Arduino and Wiring Library to produce PWM signals on any arbitrary pin.

It was originally designed for use controlling the brightness of LEDs, but could be modified to control servos and other low frequency PWM controlled devices as well.

It uses a single hardware timer (Timer 2) on the microcontroller to generate up to 20 PWM channels.

Features

• Arbitrary output pins.
• Up to 20 different channels can be created.
• True zero level, i.e. off = off
• Separate fade rates for on and off.

Notes:

This library doesn't work well with servos, so beware that it may not work as you may expect if used to control servos.

The reason being is that the SoftPWM range of values is over the entire pulse width, whereas a servo expects a pulse over a tight range (0.5 mS to 2.5 mS and repeated every 20 mS). Hence, the range of usable values for a servo or such would be something like 40 to 50 resulting in big jumps in the servo position.

Usage Example

#include <SoftPWM.h>

void setup()
{
  // Initialize
  SoftPWMBegin();

  // Create and set pin 13 to 0 (off)
  SoftPWMSet(13, 0);

  // Set fade time for pin 13 to 100 ms fade-up time, and 500 ms fade-down time
  SoftPWMSetFadeTime(13, 100, 500);
}

void loop()
{
  // Turn on - set to 100%
  SoftPWMSetPercent(13, 100);

  // Wait for LED to turn on - you could do other tasks here
  delay(100);

  // Turn off - set to 0%
  SoftPWMSetPercent(13, 0);

  // Wait for LED to turn off
  delay(500);
}

Function Descriptions

SoftPWMBegin([defaultPolarity])

• Initializes the library - sets up the timer and other tasks.
• optional defaultPolarity allows all newly defined pins to take on this polarity.
  • Values: SOFTPWM_NORMAL, SOFTPWM_INVERTED

SoftPWMSet(pin, value)

• pin is the output pin.
• value is a value between 0 and 255 (inclusive).

SoftPWMSetPercent(pin, percent)

• pin is the output pin.
• percent is a value between 0 and 100 (inclusive).

SoftPWMSetFadeTime(pin, fadeUpTime, fadeDownTime)

• pin is the output pin.
• fadeuptime is the time in milliseconds that it will take the channel to fade from 0 to 255.
  • Range: 0 to 4000
• fadedowntime is the time in milliseconds that it will take the channel to fade from 255 to 0.
  • Range: 0 to 4000

SoftPWMSetPolarity(pin, polarity)

• pin is the output pin.
• polarity is the polarity for the given pin.

Notes

• You can use ALL in place of the pin number to have the function act on all currently set channels.
  • e.g. SoftPWMSetFadeTime(ALL, 100, 400) - this will set all created channels to have a fade-up time of 100 ms and a fade-down time of 400.
• The polarity setting of the pin is as follows:
  • SOFTPWM_NORMAL means that the pin LOW when the PWM value is 0, whereas SOFTPWM_INVERTED indicates the pin should be HIGH when the PWM value is 0.

Demonstrations

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Arduino Duemilanove LED Blink example - available as library example:

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rDuino LEDHead Bounce example - available as library example:

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More demos:

http://www.youtube.com/view_play_list?p=33BB5D2E20609C52

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