Spinning a servo with elixir_ale

README.md

Spinny is an Elixir port of the Adafruit_PWM_Servo_Driver code in Adafruit's Raspberry-Pi Python Code Library

https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/tree/master/Adafruit_PWM_Servo_Driver

It uses Elixir ALE for low-level i2c communication:

https://github.com/fhunleth/elixir_ale

Page numbers refer to the PCA9685 Datasheet: https://www.adafruit.com/datasheets/PCA9685.pdf

See LICENSE.md for more info

Usage

At the command line:

$ mix run -e Spinny.start # repeatedly spin left and right

(to quit, time your ctrl-c's for when it's idle)

$ mix run -e Spinny.swrst # software reset

In iex:

$ iex -S mix
> {:ok,pid}= I2c.start_link("i2c-1", 0x40)
> Spinny.init(pid)
> Spinny.prescale(pid)
> Spinny.bump(pid)

LICENSE.md

Copyright 2015 Wendy Smoak

Spinny is an Elixir port of the Adafruit_PWM_Servo_Driver code in Adafruit's Raspberry-Pi Python Code Library

https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/tree/master/Adafruit_PWM_Servo_Driver

As such, it inherits the BSD license and the additional information shown below:

Adafruit's Raspberry-Pi Python Code Library

Here is a growing collection of libraries and example python scripts for controlling a variety of Adafruit electronics with a Raspberry Pi

In progress!

Adafruit invests time and resources providing this open source code, please support Adafruit and open-source hardware by purchasing products from Adafruit!

Written by Limor Fried, Kevin Townsend and Mikey Sklar for Adafruit Industries. BSD license, all text above and below must be included in any redistribution

To download, we suggest logging into your Pi with Internet accessibility and typing:

git clone https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code.git

============ Copyright (c) 2012-2013 Limor Fried, Kevin Townsend and Mikey Sklar for Adafruit Industries. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. * Neither the name of the nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

mix.exs

defmodule Spinny.Mixfile do
  use Mix.Project

  def project do
    [app: :spinny,
     version: "0.0.1",
     elixir: "~> 1.2-rc",
     build_embedded: Mix.env == :prod,
     start_permanent: Mix.env == :prod,
     deps: deps]
  end

  # Configuration for the OTP application
  #
  # Type "mix help compile.app" for more information
  def application do
    [applications: [:logger]]
  end

  # Dependencies can be Hex packages:
  #
  #   {:mydep, "~> 0.3.0"}
  #
  # Or git/path repositories:
  #
  #   {:mydep, git: "https://github.com/elixir-lang/mydep.git", tag: "0.1.0"}
  #
  # Type "mix help deps" for more examples and options
  defp deps do
    [ 
      {:elixir_ale, "~> 0.4.0"},          
    ]
  end
end

spinny.ex

defmodule Spinny do
  require Logger
  use Bitwise 
  
  @mode1      0x00 # bit 4 is SLEEP 000X0000
  @mode2      0x01
  @prescale   0xFE

  @all_on_l   0xFA
  @all_on_h   0xFB
  @all_off_l  0xFC
  @all_off_h  0xFD

  @led0_on_l  0x06
  @led0_on_h  0x07
  @led0_off_l 0x08
  @led0_off_h 0x09
  
  @allcall 0x01
  @outdrv 0x04
  @swrst 0x06

  def start do
    Logger.debug "Starting..."
    {:ok,pid}= I2c.start_link("i2c-1", 0x40) # PCA9685 default address

    init(pid)
    prescale(pid, 60) # set pwm to 60 Hz 
    spin(pid)
  end

  # PCA9685 Software Reset (Section 7.6 on pg 28)
  def swrst do
    Logger.debug "PCA9685 Software Reset..."
    {:ok,pid}=I2c.start_link("i2c-1", 0x00)
    :timer.sleep 10
    I2c.write(pid,<<@swrst>>)
  end

  def init(pid) do
    Logger.debug "Initializing..."
    
    set_all_pwm(pid,0,0) 

    I2c.write(pid, <<@mode2, @outdrv>>) # external driver, see docs
    I2c.write(pid, <<@mode1, @allcall>>) # program all PCA9685's at once
    :timer.sleep 5 
  end

  def prescale(pid,freq) do
    Logger.debug "Setting prescale to #{freq} Hz" 

    # pg 14 and solve for prescale or example on pg 25
    prescaleval = trunc(Float.round( 25000000.0 / 4096.0 / freq ) - 1 )
    Logger.debug "prescale value is #{prescaleval}"

    oldmode = I2c.write_read(pid, <<@mode1>>, 1)
    :timer.sleep 5
    I2c.write(pid, <<@mode1, 0x11>>) # set bit 4 (sleep) to allow setting prescale
    I2c.write(pid, <<@prescale, prescaleval>> )
    I2c.write(pid, <<@mode1, 0x01>> ) #un-set sleep bit
    :timer.sleep 5 # pg 14 it takes 500 us for the oscillator to be ready

    I2c.write(pid, <<@mode1>> <> oldmode ) # put back old mode

  end
 
  # spin one way
  def min(pid) do
    Logger.debug "min"
    set_pwm(pid, 0, 0, 0x0096)
  end
 
  # spin the other way  
  def max(pid) do
    Logger.debug "max"
    set_pwm(pid, 0, 0, 0x0258)
  end
 
  # stop 
  def mid(pid) do
    Logger.debug "mid"
    set_pwm(pid, 0, 0, 0)
  end

  # spins just a bit in one direction and stops
  def bump(pid) do
    Logger.debug "bump"
    max(pid)
    :timer.sleep 200
    mid(pid)
  end

  # repeatedly spins one way, then the other
  # to quit, time your ctrl-c's for when it is idle
  # or it will be left spinning forever
  def spin(pid) do
    min(pid) 
    :timer.sleep 1000
  
    mid(pid)
    :timer.sleep 1000
   
    max(pid)
    :timer.sleep 1000
    
    mid(pid)
    :timer.sleep 1000
 
    spin(pid)
  end

  # The registers for each of the 16 channels are sequential
  # so the address can be calculated as an offset from the first one
  def set_pwm(pid, channel, on, off) do
    I2c.write(pid, <<@led0_on_l+4*channel, on &&& 0xFF>>)
    I2c.write(pid, <<@led0_on_h+4*channel, on >>> 8>>)
    I2c.write(pid, <<@led0_off_l+4*channel, off &&& 0xFF>>) 
    I2c.write(pid, <<@led0_off_h+4*channel, off >>> 8>>)
  end

  # The PCA9685 has special registers for setting ALL channels
  # (or 1/3 of them) to the same value. 
  def set_all_pwm(pid, on, off) do
    I2c.write(pid, <<@all_on_l, on &&& 0xFF>>)
    I2c.write(pid, <<@all_on_h, on >>> 8>>)
    I2c.write(pid, <<@all_off_l, off &&& 0xFF>>)
    I2c.write(pid, <<@all_off_h, off >>> 8>>)
  end
end