rlm@8: // The MIT License
rlm@8: 
rlm@8: // Copyright (c) 2009 Massachusetts Institute of Technology
rlm@8: 
rlm@8: // Permission is hereby granted, free of charge, to any person obtaining a copy
rlm@8: // of this software and associated documentation files (the "Software"), to deal
rlm@8: // in the Software without restriction, including without limitation the rights
rlm@8: // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
rlm@8: // copies of the Software, and to permit persons to whom the Software is
rlm@8: // furnished to do so, subject to the following conditions:
rlm@8: 
rlm@8: // The above copyright notice and this permission notice shall be included in
rlm@8: // all copies or substantial portions of the Software.
rlm@8: 
rlm@8: // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
rlm@8: // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
rlm@8: // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
rlm@8: // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
rlm@8: // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
rlm@8: // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
rlm@8: // THE SOFTWARE.
rlm@8: 
rlm@8: // Author: Kermin Fleming kfleming@mit.edu
rlm@8: 
rlm@8: import Connectable::*;
rlm@8: import GetPut::*;
rlm@8: import ClientServer::*;
rlm@8: import FIFO::*;
rlm@8: import FixedPoint::*;
rlm@8: import Vector::*;
rlm@8: 
rlm@8: //AWB includes.   These import the structure whcih allow us to communicate
rlm@8: // with the outside world, and are part of the AWB library code
rlm@8: 
rlm@8: `include "asim/provides/soft_connections.bsh"
rlm@8: `include "asim/provides/common_services.bsh"
rlm@8: 
rlm@8: // Local includes. Look for the correspondingly named .awb files
rlm@8: // workspace/labs/src/mit-6.375/modules/bluespec/mit-6.375/common/
rlm@8: // to find the actual Bluespec files which are used to generate
rlm@8: // these includes.  These files are specific to this audio processing
rlm@8: // pipeline
rlm@8: 
rlm@8: `include "asim/provides/audio_pipeline_types.bsh"
rlm@8: `include "asim/provides/audio_processor_types.bsh"
rlm@8: 
rlm@8: typedef 8 Taps;
rlm@8: 
rlm@8: module [Connected_Module] mkFIRFilter (FIRFilter);
rlm@8: 
rlm@8: 
rlm@8:   // instantiate an input FIFO and an Output FIFO
rlm@8:   // mkFIFO returns a fifo of length 2 (by default)  
rlm@8:   // AudioProcessorUnit is the name given to the packets
rlm@8:   // of DATA processed by our audio pipeline.  For their 
rlm@8:   // definition, look in the file
rlm@8:   // workspace/labs/src/mit-6.375/modules/bluespec/mit-6.375/common/AudioProcessorTypes.bsv
rlm@8: 
rlm@8:   FIFO#(AudioProcessorUnit) infifo <- mkFIFO;
rlm@8:   FIFO#(AudioProcessorUnit) outfifo <- mkFIFO;
rlm@8: 
rlm@8: 
rlm@8:   // an alternate syntax for instantiating the samples vector
rlm@8:   // would have been as follows:
rlm@8:   //
rlm@8:   // Vector#(Taps,Reg#(Sample)) samples <- replicateM(mkReg(0));
rlm@8:   // 
rlm@8:   // we have used an explicit loop here, to demonstrate how
rlm@8:   // vectors can be instantiated during the static elaboration 
rlm@8:   // phase, even though replicateM is far more concise.
rlm@8: 
rlm@8:   Vector#(Taps,Reg#(Sample)) samples = newVector();
rlm@8:   for(Integer i = 0; i < valueof(Taps); i=i+1)
rlm@8:      samples[i] <- mkReg(0);
rlm@8: 
rlm@8:   Vector#(9,Reg#(FixedPoint#(16,16))) pr <- replicateM(mkReg(0));
rlm@8:   
rlm@8: 
rlm@8:   // fromReal takes a Real number and converts it to a FixedPoint
rlm@8:   // representation.   The compiler is smart enough to infer the 
rlm@8:   // type (bit width) of the fixed point (in this case, we have 16 
rlm@8:   // bits of integer, and 16 bits of fraction.
rlm@8: 
rlm@8:   FixedPoint#(16,16) firCoefs [9] = {fromReal(-0.0124),
rlm@8:                                      fromReal(0.0),
rlm@8:                                      fromReal(-0.0133),
rlm@8:                                      fromReal(0.0),
rlm@8:                                      fromReal(0.8181),
rlm@8:                                      fromReal(0.0),
rlm@8:                                      fromReal(-0.0133),
rlm@8:                                      fromReal(0.0),
rlm@8:                                      fromReal(-0.0124)};
rlm@8: 
rlm@8: 
rlm@8:   // This rule implements a fir filter.  We do the fir computations in
rlm@8:   // 16.16 fixed point.  This preserves the magnitude of the input
rlm@8:   // pcm.  This code was implemented using for loops so as to be more
rlm@8:   // clear. Using the functions map, fold, readVReg, and writeVReg
rlm@8:   // would have been more concise.
rlm@8: 
rlm@8:   rule process (infifo.first matches tagged Sample .sample);
rlm@8: 
rlm@8:     // Advance the fir filter, by shifting all the elements
rlm@8:     // down the Vector of registers (like a shift register)
rlm@8: 
rlm@8:     samples[0] <= sample;
rlm@8:     for(Integer i = 0; i < valueof(Taps) - 1; i = i + 1)
rlm@8:        begin
rlm@8:          samples[i+1] <= samples[i];           
rlm@8:        end
rlm@8: 
rlm@8:     // Filter the values, using an inefficient adder chain.  You will
rlm@8:     // need to shorten the combinatorial path, by pipelining this logic.
rlm@8: 
rlm@8:     FixedPoint#(16,16) accumulate= firCoefs[0] * fromInt(sample);  
rlm@8:     for(Integer i = 0; i < valueof(Taps); i = i + 1)
rlm@8:       begin
rlm@8:         accumulate = accumulate + firCoefs[1+i] * fromInt(samples[i]);  
rlm@8:       end 
rlm@8: 
rlm@8:     outfifo.enq(tagged Sample fxptGetInt(accumulate));
rlm@8:     
rlm@8:     infifo.deq;
rlm@8:   endrule
rlm@8:   
rlm@8:   // Handle the end of stream condition.  Look at the two rule guards,
rlm@8:   // these are obviously mutually exclusive.  The definition of
rlm@8:   // AudioProcessorUnit shows that it can be tagged only as a Sample, or
rlm@8:   // EndOfFile; nothing else!
rlm@8: 
rlm@8:   rule endOfFile (infifo.first matches tagged EndOfFile);
rlm@8: 
rlm@8:     $display("FIR got end of file");
rlm@8: 
rlm@8:     // Reset state for next invocation
rlm@8:     for(Integer i = 0; i < valueof(Taps); i = i + 1)
rlm@8:       begin
rlm@8:         samples[i] <= 0;
rlm@8:         pr[i] <= 0;
rlm@8:       end
rlm@8: 
rlm@8:     // pass the end-of-file token down the pipeline, eventually this will
rlm@8:     // make it back to the software side, to notify it that the stream
rlm@8:     // has been processed completely
rlm@8: 
rlm@8:     outfifo.enq(infifo.first);
rlm@8:     infifo.deq;
rlm@8:   endrule
rlm@8: 
rlm@8: 
rlm@8:   // this section connects the fifos instantiated internally to the 
rlm@8:   // externally visible interface
rlm@8: 
rlm@8:   interface sampleInput = fifoToPut(infifo);
rlm@8:   interface sampleOutput = fifoToGet(outfifo);
rlm@8: 
rlm@8: endmodule