Verilog Code for FIR Filter

FIR filters are is widely used in different applications such as biomedical, communication and control due to its easily implementation, stability and best performance. Its simplicity makes it attractive for many applications where it is need to minimize computational requirements.

Below is the code for FIR Filter , Any comments/doubts are welcome.

Please contact me if you want a soft copy of the module.

Block diagram :

F is the flopped stage and C1/C2/C3/C4/C5  are the coefficient. One bug adder will required to add all the feedback.

Below is the verilog code for FIR filter with test bench.
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module fir_filter (  a, b, clk, rstn) ;

input signed [31:0] a;
output signed [31:0] b;
input clk;
input rstn;


parameter avg = 20;
parameter  c1 = avg*(8'h1) ;
parameter  c2 = avg*(8'h1) ;
parameter  c3 = avg*(8'h1) ;
parameter  c4 = avg*(8'h1) ;
parameter  c5 = avg*(8'h1) ;


reg signed [31:0] f1 ;
reg signed [31:0] f2 ;
reg signed [31:0] f3 ;
reg signed [31:0] f4 ;
reg signed [31:0] f5 ;


always @(posedge clk or negedge rstn) begin
  if(!rstn)  begin
    f1 <= 32'b0;
    f2 <= 32'b0;
    f3 <= 32'b0;
    f4 <= 32'b0;
    f5 <= 32'b0;
  end
  else begin
    f1 <= a;
    f2 <= f1;
    f3 <= f2;
    f4 <= f3;
    f5 <= f4;
  end
end


assign b = (f1*c1 + f2*c2 + f3*c3 + f4*c4 + f5*c5)/(5*avg) ;


endmodule

module tb_fir;

reg [31:0] in_signal;
reg clk =0;
reg rstn =0;
reg en =0;
wire [31:0] out_signal;

always #5 clk = ~clk;

integer cnt=0;

always @(clk) cnt = cnt +1 ;

always @(*) begin
   if(en ==1 && cnt[2:0] == 3'b111) begin
   #1;
  in_signal = cnt[7:0];
  end
  end

fir_filter dut (
.a(in_signal),
.b(out_signal),
.clk(clk),
.rstn(rstn));

initial begin
  rstn =0 ;
  #100;
  rstn = 1;
  en =1;
  #10000 ;
  $finish;
end

initial
 $monitor("Input signal = %d , out_signal = %d", in_signal, out_signal);

initial begin
  $recordfile("test.trn");
  $recordvars();
  end

endmodule

------------------------- verilog code end -------------------- 

Downloads the verilog file here. 

fir_filter.v