example of jah's MMFilter module for R engine

mmf_example.lua

engine.name = 'R'

local R = require 'r/lib/r'
local Option = require 'params/option'
local Formatters = require 'formatters'
local KEY2 = 0
local edit = "cutoff"

function init()
  engine.new("LP", "MMFilter")
  engine.new("HP", "MMFilter")
  engine.new("SoundIn", "SoundIn")
  engine.new("SoundOut", "SoundOut")

  engine.connect("SoundIn/Left", "LP/In")
  engine.connect("SoundIn/Right", "HP/In")
  engine.connect("LP/Lowpass", "SoundOut/Left")
  engine.connect("HP/Highpass", "SoundOut/Right")
  
  filter_frequency_spec = R.specs.MMFilter.Frequency:copy()
  filter_frequency_spec.default = 2000
  
  params:add {
    type="control",
    id="LPfrequency",
    name="LP.Frequency",
    controlspec=filter_frequency_spec,
    action=function(value) engine.set("LP.Frequency", value) end
  }
  
  params:add {
    type="control",
    id="HPfrequency",
    name="HP.Frequency",
    controlspec=filter_frequency_spec,
    action=function(value) engine.set("HP.Frequency", value) end
  }
  
  local filter_resonance_spec = R.specs.MMFilter.Resonance:copy()
  filter_resonance_spec.default = 0.4
  
  params:add {
    type="control",
    id="LPresonance",
    name="LP.Resonance",
    controlspec=filter_resonance_spec,
    formatter=Formatters.percentage,
    action=function(value) engine.set("LP.Resonance", value) end
  }

  params:add {
    type="control",
    id="HPresonance",
    name="HP.Resonance",
    controlspec=filter_resonance_spec,
    formatter=Formatters.percentage,
    action=function(value) engine.set("HP.Resonance", value) end
  }

  params:read()
  params:bang()

end

function enc(n, delta)
  if n == 1 then
    mix:delta("output", delta)
  elseif n == 2 then
    if KEY2 == 1 then
      params:delta("LPresonance", delta)
    else
      params:delta("LPfrequency", delta)
    end
  elseif n == 3 then
    if KEY2 == 1 then
      params:delta("HPresonance", delta)
    else
      params:delta("HPfrequency", delta)
    end
  end
  redraw()
end

function key(n,z)
  if n == 2 and z == 1 then
    KEY2 = 1
    edit = "resonance"
  else
    KEY2 = 0
    edit = "cutoff"
  end
  redraw()
end

function redraw()
  screen.clear()
  screen.font_size(8)
  screen.level(15)
  screen.move(0, 10)
  screen.level(edit=="cutoff" and 15 or 2)
  screen.text("LP Cutoff: "..params:string("LPfrequency"))
  screen.move(0, 20)
  screen.level(edit=="resonance" and 15 or 2)
  screen.text("LP Resonance: "..params:string("LPresonance"))
  screen.move(0,40)
  screen.level(edit=="cutoff" and 15 or 2)
  screen.text("HP Cutoff: "..params:string("HPfrequency"))
  screen.move(0, 50)
  screen.level(edit=="resonance" and 15 or 2)
  screen.text("HP Resonance: "..params:string("HPresonance"))
  screen.update()
end