add reference generator

README.md

@@ -61,6 +61,7 @@ for (i,t) = enumerate(0:h:duration)
 end
 ```
 
+
 Often one finds the need to implement a stateful controller, i.e., a function
 that has a memory or state. To this end, the function [`sysfilter`](@ref) is
 provided. This function is used to implement control loops where a signal is

src/LabProcesses.jl

@@ -9,6 +9,7 @@ include("interface_documentation.jl")
 include("interface_implementations/ballandbeam.jl")
 
 include("utilities.jl")
+include("reference_generators.jl")
 include("controllers.jl")
 
 end # module

src/reference_generators.jl

+export PRBSGenerator
+
+#PRBS
+"""
+    r = PRBSGenerator(state = 1)
+Generates a pseudo-random binary sequence. Call like `random_input = r()`.
+"""
+mutable struct PRBSGenerator
+    state::Int
+end
+
+PRBSGenerator() = PRBSGenerator(Int(1))
+
+function (r::PRBSGenerator)(args...)
+    state = r.state
+    bit   = ((state >> 0) ⊻ (state >> 2) ⊻ (state >> 3) ⊻ (state >> 5) ) & 1
+    r.state = (state >> 1) | (bit << 15)
+    bit
+end

test/runtests.jl

 using LabProcesses
 using Base.Test
 
-# write your own tests here
-@test 1 == 2
+# Reference generators
+r = PRBSGenerator(Int(1))
+seq = [r() for i = 1:10]
+@test all(seq .==  [0, 0, 1, 0, 0, 1, 1, 0, 0, 1])
+foreach(r,1:10_000)