Add second-order direct form IIR example

b_asic/__init__.py

@@ -5,7 +5,7 @@ ASIC toolbox that simplifies circuit design and optimization.
 # NOTE: If this import gives an error,
 # make sure the C++ module has been compiled and installed properly.
 # See the included README.md for more information on how to build/install.
-from _b_asic import *
+# from _b_asic import *
 # Python modules.
 from b_asic.core_operations import *
 from b_asic.graph_component import *

b_asic/schedule.py

@@ -317,10 +317,11 @@ class Schedule:
             x = np.array(_x)
             y = np.array(_y)
             plt.fill(x + op_start_time, y + ypos)
-            _x, _y = zip(*execution_time_coords)
-            x = np.array(_x)
-            y = np.array(_y)
-            plt.plot(x + op_start_time, y + ypos, color='black', linewidth=3, alpha=0.5)
+            if execution_time_coords:
+                _x, _y = zip(*execution_time_coords)
+                x = np.array(_x)
+                y = np.array(_y)
+                plt.plot(x + op_start_time, y + ypos, color='black', linewidth=3, alpha=0.5)
             ytickpositions.append(ypos + 0.5)
             yticklabels.append(self._sfg.find_by_id(op_id).name)
             ypositions[op_id] = ypos

examples/secondorderdirectformiir.py

+"""A sfg with delays and interesting layout for precednce list generation.
+     .                                          .
+IN1>--->C0>--->ADD1>----------+--->A0>--->ADD4>--->OUT1
+     .           ^            |            ^    .
+     .           |            T1           |    .
+     .           |            |            |    .
+     .         ADD2<---<B1<---+--->A1>--->ADD3  .
+     .           ^            |            ^    .
+     .           |            T2           |    .
+     .           |            |            |    .
+     .           +-----<B2<---+--->A2>-----+    .
+"""
+
+from b_asic.core_operations import Addition, ConstantMultiplication
+from b_asic.special_operations import Delay, Input, Output
+from b_asic.signal_flow_graph import SFG
+from b_asic.schedule import Schedule
+
+
+in1 = Input("IN1")
+c0 = ConstantMultiplication(5, in1, "C0")
+add1 = Addition(c0, None, "ADD1")
+# Not sure what operation "Q" is supposed to be in the example
+T1 = Delay(add1, 0, "T1")
+T2 = Delay(T1, 0, "T2")
+b2 = ConstantMultiplication(0.2, T2, "B2")
+b1 = ConstantMultiplication(0.3, T1, "B1")
+add2 = Addition(b1, b2, "ADD2")
+add1.input(1).connect(add2)
+a1 = ConstantMultiplication(0.4, T1, "A1")
+a2 = ConstantMultiplication(0.6, T2, "A2")
+add3 = Addition(a1, a2, "ADD3")
+a0 = ConstantMultiplication(0.7, add1, "A0")
+add4 = Addition(a0, add3, "ADD4")
+out1 = Output(add4, "OUT1")
+
+sfg = SFG(inputs=[in1], outputs=[out1], name="Second-order direct form IIR filter")
+
+# Set latencies and exection times
+sfg.set_latency_of_type(ConstantMultiplication.type_name(), 2)
+sfg.set_latency_of_type(Addition.type_name(), 1)
+sfg.set_execution_time_of_type(ConstantMultiplication.type_name(), 1)
+sfg.set_execution_time_of_type(Addition.type_name(), 1)
+
+schedule = Schedule(sfg)