Same old RC Filter Simulation in Julia

rc_filter_simulation.jl

abstract PassiveComponent

type Resistor <: PassiveComponent
  value::Complex{Float64}
end

type Capacitor <: PassiveComponent
  value::Complex{Float64}
end

type RCFilter
  voltage::Real
  frequency::Real
  resistor::Resistor
  capacitor::Capacitor
end


function resistance(capacitor::Capacitor)
  0
end

function impedance(resistor::Resistor, frequency::Real = 0)
  resistor.value
end

function impedance(capacitor::Capacitor, frequency::Real = 0)
  (2π * frequency * capacitor.value)^-1
end

function set_input(filter::RCFilter, voltage::Real, frequency::Real = 0)
  filter.voltage = voltage
  filter.frequency = frequency
end

function cutoff(filter::RCFilter)
  (2π * filter.resistor.value * filter.capacitor.value)^-1
end

function total_impedance(filter::RCFilter)
  impedance(filter.resistor, filter.frequency) + impedance(filter.capacitor, filter.frequency)
end

function total_current(filter::RCFilter)
  filter.voltage / total_impedance(filter)
end

function voltage_across_resistor(filter::RCFilter)
  total_current(filter) * impedance(filter.resistor, filter.frequency)
end

function voltage_across_capacitor(filter::RCFilter)
  total_current(filter) * impedance(filter.capacitor, filter.frequency)
end

function frequency_sweep(filter::RCFilter)
  map(0:2:127) do midi
    f = 440 * 2^((midi - 69) / 12.0)
    set_input(filter, 1.0, f)
    abs(voltage_across_capacitor(filter))
  end
end

function print_frequency_response_graph(filter::RCFilter)
  line = repeat("-", 64)
  response = map(frequency_sweep(filter)) do voltage
    round(Int64, (voltage * 10))
  end

  println("Frequency Response:")
  println(line)
  for voltage in 10:-1:0
    print("|")
    for r in response
      print(voltage == r ? "*" : " ")
    end
    println("|")
  end
  println(line)
end

r1 = 1.0                # R1 = 220 Ohms
c1 = 0.0001            # C1 = 1uF

filter = RCFilter(1, 0, Resistor(r1), Capacitor(c1))
#fc = cutoff(filter)
print_frequency_response_graph(filter)