examples/fir.py

   1 from scipy import signal
   2 from math import cos, pi
   3
   4 from migen.fhdl.structure import *
   5 from migen.fhdl import verilog
   6 from migen.corelogic.misc import optree
   7 from migen.fhdl import autofragment
   8 from migen.sim.generic import Simulator
   9 from migen.sim.icarus import Runner
  10
  11 class FIR:
  12         def __init__(self, coef, wsize=16):
  13                 self.coef = coef
  14                 self.wsize = wsize
  15                 self.i = Signal(BV(self.wsize, True))
  16                 self.o = Signal(BV(self.wsize, True))
  17
  18         def get_fragment(self):
  19                 muls = []
  20                 sync = []
  21                 src = self.i
  22                 for c in self.coef:
  23                         sreg = Signal(BV(self.wsize, True))
  24                         sync.append(sreg.eq(src))
  25                         src = sreg
  26                         c_fp = int(c*2**(self.wsize - 1))
  27                         c_e = Constant(c_fp, BV(bits_for(c_fp), True))
  28                         muls.append(c_e*sreg)
  29                 sum_full = Signal(BV(2*self.wsize-1, True))
  30                 sync.append(sum_full.eq(optree("+", muls)))
  31                 comb = [self.o.eq(sum_full[self.wsize-1:])]
  32                 return Fragment(comb, sync)
  33
  34 class TB:
  35         def __init__(self, fir, frequency):
  36                 self.fir = fir
  37                 self.frequency = frequency
  38                 self.inputs = []
  39                 self.outputs = []
  40
  41         def do_simulation(self, s):
  42                 f = 2**(self.fir.wsize - 1)
  43                 v = 0.1*cos(2*pi*self.frequency*s.cycle_counter)
  44                 s.wr(self.fir.i, int(f*v))
  45                 self.inputs.append(v)
  46                 self.outputs.append(s.rd(self.fir.o)/f)
  47
  48         def get_fragment(self):
  49                 return Fragment(sim=[self.do_simulation])
  50
  51 def main():
  52         coef = signal.remez(80, [0, 0.1, 0.1, 0.5], [1, 0])
  53         fir = FIR(coef)
  54         tb = TB(fir, 0.3)
  55         fragment = autofragment.from_local()
  56         sim = Simulator(fragment, Runner())
  57         sim.run(200)
  58         print(tb.inputs)
  59         print(tb.outputs)
  60
  61 main()