From 57a87b33165d778101c275d30d58a1f67b67c130 Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sebastien@milkymist.org>
Date: Thu, 8 Mar 2012 20:49:36 +0100
Subject: [PATCH] examples: FIR filter simulation

---
 examples/fir.py | 61 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 examples/fir.py

diff --git a/examples/fir.py b/examples/fir.py
new file mode 100644
index 000000000..b5d366e8d
--- /dev/null
+++ b/examples/fir.py
@@ -0,0 +1,61 @@
+from scipy import signal
+from math import cos, pi
+
+from migen.fhdl.structure import *
+from migen.fhdl import verilog
+from migen.corelogic.misc import optree
+from migen.fhdl import autofragment
+from migen.sim.generic import Simulator
+from migen.sim.icarus import Runner
+
+class FIR:
+	def __init__(self, coef, wsize=16):
+		self.coef = coef
+		self.wsize = wsize
+		self.i = Signal(BV(self.wsize, True))
+		self.o = Signal(BV(self.wsize, True))
+	
+	def get_fragment(self):
+		muls = []
+		sync = []
+		src = self.i
+		for c in self.coef:
+			sreg = Signal(BV(self.wsize, True))
+			sync.append(sreg.eq(src))
+			src = sreg
+			c_fp = int(c*2**(self.wsize - 1))
+			c_e = Constant(c_fp, BV(bits_for(c_fp), True))
+			muls.append(c_e*sreg)
+		sum_full = Signal(BV(2*self.wsize-1, True))
+		sync.append(sum_full.eq(optree("+", muls)))
+		comb = [self.o.eq(sum_full[self.wsize-1:])]
+		return Fragment(comb, sync)
+
+class TB:
+	def __init__(self, fir, frequency):
+		self.fir = fir
+		self.frequency = frequency
+		self.inputs = []
+		self.outputs = []
+	
+	def do_simulation(self, s):
+		f = 2**(self.fir.wsize - 1)
+		v = 0.1*cos(2*pi*self.frequency*s.cycle_counter)
+		s.wr(self.fir.i, int(f*v))
+		self.inputs.append(v)
+		self.outputs.append(s.rd(self.fir.o)/f)
+	
+	def get_fragment(self):
+		return Fragment(sim=[self.do_simulation])
+
+def main():
+	coef = signal.remez(80, [0, 0.1, 0.1, 0.5], [1, 0])
+	fir = FIR(coef)
+	tb = TB(fir, 0.3)
+	fragment = autofragment.from_local()
+	sim = Simulator(fragment, Runner())
+	sim.run(200)
+	print(tb.inputs)
+	print(tb.outputs)
+
+main()