add example architecture for second order direct-form IIR filter

examples/secondorderdirectformiir_architecture.py

+"""
+=====================================
+Second-order IIR Filter with Schedule
+=====================================
+
+"""
+
+from b_asic.architecture import Architecture, Memory, ProcessingElement
+from b_asic.core_operations import Addition, ConstantMultiplication
+from b_asic.schedule import Schedule
+from b_asic.signal_flow_graph import SFG
+from b_asic.special_operations import Delay, Input, Output
+
+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 execution 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)
+
+# %%
+# Create schedule
+
+schedule = Schedule(sfg, cyclic=True)
+schedule.show()
+
+# Rescheudle
+schedule.move_operation('add4', 3)
+schedule.move_operation('cmul5', -1)
+schedule.move_operation('cmul4', -1)
+schedule.move_operation('cmul5', -3)
+schedule.move_operation('cmul4', -3)
+schedule.move_operation('cmul4', -1)
+schedule.move_operation('cmul6', -1)
+schedule.move_operation('cmul6', -1)
+schedule.move_operation('cmul3', 1)
+schedule.move_operation('cmul4', 1)
+schedule.move_operation('cmul5', -1)
+
+# ARch
+operations = schedule.get_operations()
+adders = operations.get_by_type_name('add')
+mults = operations.get_by_type_name('cmul')
+inputs = operations.get_by_type_name('in')
+outputs = operations.get_by_type_name('out')
+p1 = ProcessingElement(adders, entity_name="adder")
+p2 = ProcessingElement(mults, entity_name="cmul")
+p_in = ProcessingElement(inputs, entity_name='in')
+p_out = ProcessingElement(outputs, entity_name='out')
+
+# Memories
+mem_vars = schedule.get_memory_variables()
+direct, mem_vars = mem_vars.split_on_length()
+mem = Memory(mem_vars, entity_name="memory")
+
+arch = Architecture({p1, p2, p_in, p_out}, {mem}, direct_interconnects=direct)