Estoy implementando un filtro FIR en Verilog, usando la placa DE2. Por alguna razón, la salida de los altavoces está llena de estática, aunque parece que filtra algunas frecuencias. Aquí está el código para el FIR:
// Local wires.
wire read_ready, write_ready, read, write;
wire [23:0] readdata_left, readdata_right;
wire [23:0] writedata_left, writedata_right;
assign writedata_left = output_sample;
assign writedata_right = output_sample;
assign read = 1;
assign write = 1;
wire [23:0] input_sample = readdata_left;
reg [23:0] output_sample;
La muestra de entrada se coloca a través del FIR y la muestra de salida se coloca en los altavoces izquierdo y derecho para simplificar.
//The FIR filter
parameter N = 40;
reg signed[23:0] coeffs[39:0];
reg [23:0] holderBefore[39:0];
wire [23:0] toAdd[39:0];
// -- 1000-1100
always @(*)
begin
coeffs[0]=24'b100000000110101001111110; // -- 1
coeffs[1]=24'b100000000110100011011011; // -- 2
coeffs[2]=24'b100000000111000100001100; // -- 3
coeffs[3]=24'b100000000111111000101000;// -- 4
coeffs[4]=24'b100000001000011111111100;// -- 5
coeffs[5]=24'b100000001000011001011001;// -- 6
coeffs[6]=24'b100000000111010001010011;// -- 7
coeffs[7]=24'b100000000100100110111010;// -- 8
coeffs[8]=24'b100000000000011010001101;// -- 9
coeffs[9]=24'b000000000101101111000000;// -- 10
coeffs[10]=24'b000000001101100001000100;// -- 11
coeffs[11]=24'b000000010110111100000000;// -- 12
coeffs[12]=24'b000000100001011111000001;// -- 13
coeffs[13]=24'b000000101100101001010111;// -- 14
coeffs[14]=24'b000000111000000000110100;// -- 15
coeffs[15]=24'b000001000010101010011001;// -- 16
coeffs[16]=24'b000001001100001011111000;// -- 17
coeffs[17]=24'b000001010011111101111100;// -- 18
coeffs[18]=24'b000001011001011001010010;// -- 19
coeffs[19]=24'b000001011100010000110010;// -- 20
coeffs[20]=24'b000001011100010000110010;// -- 20
coeffs[21]=24'b000001011001011001010010;// -- 19
coeffs[22]=24'b000001001100001011111000;// -- 18
coeffs[23]=24'b000001001100001011111000;// -- 17
coeffs[24]=24'b000001000010101010011001;// -- 16
coeffs[25]=24'b000000111000000000110100;// -- 15
coeffs[26]=24'b000000101100101001010111;// -- 14
coeffs[27]=24'b000000100001011111000001;// -- 13
coeffs[28]=24'b000000010110111100000000;// -- 12
coeffs[29]=24'b000000001101100001000100;// -- 11
coeffs[30]=24'b000000000101101111000000;// -- 10
coeffs[31]=24'b100000000000011010001101;// -- 9
coeffs[32]=24'b100000000100100110111010;// -- 8
coeffs[33]=24'b100000000111010001010011;// -- 7
coeffs[34]=24'b100000001000011001011001;// -- 6
coeffs[35]=24'b100000001000011111111100;// -- 5
coeffs[36]=24'b100000000111111000101000;// -- 4
coeffs[37]=24'b100000000111000100001100;// -- 3
coeffs[38]=24'b100000000110100011011011;// -- 2
coeffs[39]=24'b100000000110101001111110;// -- 1
end
genvar i;
generate
for (i=0; i<N; i=i+1)
begin: mult
multiplier mult1(
.dataa(coeffs[i]),
.datab(holderBefore[i]),
.out(toAdd[i]));
end
endgenerate
always @(posedge CLOCK_50 or posedge reset)
begin
if(reset)
begin
holderBefore[39] <= 0;
holderBefore[38] <= 0;
holderBefore[37] <= 0;
holderBefore[36] <= 0;
holderBefore[35] <= 0;
holderBefore[34] <= 0;
holderBefore[33] <= 0;
holderBefore[32] <= 0;
holderBefore[31] <= 0;
holderBefore[30] <= 0;
holderBefore[29] <= 0;
holderBefore[28] <= 0;
holderBefore[27] <= 0;
holderBefore[26] <= 0;
holderBefore[25] <= 0;
holderBefore[24] <= 0;
holderBefore[23] <= 0;
holderBefore[22] <= 0;
holderBefore[21] <= 0;
holderBefore[20] <= 0;
holderBefore[19] <= 0;
holderBefore[18] <= 0;
holderBefore[17] <= 0;
holderBefore[16] <= 0;
holderBefore[15] <= 0;
holderBefore[14] <= 0;
holderBefore[13] <= 0;
holderBefore[12] <= 0;
holderBefore[11] <= 0;
holderBefore[10] <= 0;
holderBefore[9] <= 0;
holderBefore[8] <= 0;
holderBefore[7] <= 0;
holderBefore[6] <= 0;
holderBefore[5] <= 0;
holderBefore[4] <= 0;
holderBefore[3] <= 0;
holderBefore[2] <= 0;
holderBefore[1] <= 0;
holderBefore[0] <= 0;
output_sample <= 0;
end
else
begin
holderBefore[39] <= holderBefore[38];
holderBefore[38] <= holderBefore[37];
holderBefore[37] <= holderBefore[36];
holderBefore[36] <= holderBefore[35];
holderBefore[35] <= holderBefore[34];
holderBefore[34] <= holderBefore[33];
holderBefore[33] <= holderBefore[32];
holderBefore[32] <= holderBefore[31];
holderBefore[31] <= holderBefore[30];
holderBefore[30] <= holderBefore[29];
holderBefore[29] <= holderBefore[28];
holderBefore[28] <= holderBefore[27];
holderBefore[27] <= holderBefore[26];
holderBefore[26] <= holderBefore[25];
holderBefore[25] <= holderBefore[24];
holderBefore[24] <= holderBefore[23];
holderBefore[23] <= holderBefore[22];
holderBefore[22] <= holderBefore[21];
holderBefore[21] <= holderBefore[20];
holderBefore[20] <= holderBefore[19];
holderBefore[19] <= holderBefore[18];
holderBefore[18] <= holderBefore[17];
holderBefore[17] <= holderBefore[16];
holderBefore[16] <= holderBefore[15];
holderBefore[15] <= holderBefore[14];
holderBefore[14] <= holderBefore[13];
holderBefore[13] <= holderBefore[12];
holderBefore[12] <= holderBefore[11];
holderBefore[11] <= holderBefore[10];
holderBefore[10] <= holderBefore[9];
holderBefore[9] <= holderBefore[8];
holderBefore[8] <= holderBefore[7];
holderBefore[7] <= holderBefore[6];
holderBefore[6] <= holderBefore[5];
holderBefore[5] <= holderBefore[4];
holderBefore[4] <= holderBefore[3];
holderBefore[3] <= holderBefore[2];
holderBefore[2] <= holderBefore[1];
holderBefore[1] <= holderBefore[0];
holderBefore[0] <= input_sample;
output_sample <= (input_sample + toAdd[0] + toAdd[1] +
toAdd[2] + toAdd[3] + toAdd[4] + toAdd[5] +
toAdd[6] + toAdd[7] + toAdd[8] + toAdd[9] +
toAdd[10] + toAdd[11] + toAdd[12]+ toAdd[13] + toAdd[14] +
toAdd[15] + toAdd[16] + toAdd[17] + toAdd[18] +
toAdd[19] + toAdd[20] + toAdd[21] + toAdd[22] +
toAdd[23] + toAdd[24] + toAdd[25] +toAdd[26] + toAdd[27] + toAdd[28] + toAdd[29] +
toAdd[19] + toAdd[20] + toAdd[21] + toAdd[22] +
toAdd[30] + toAdd[31] + toAdd[32]+ toAdd[33] + toAdd[34] + toAdd[35] + toAdd[36] +
toAdd[37] + toAdd[38] + toAdd[39]);
end
end
//The multiplier
module multiplier (dataa,datab,out);
input [23:0]dataa;
input [23:0]datab;
reg [47:0]result;
output[23:0]out;
always@(*)begin
result = dataa*datab;
end
assign out = result[46:24];
endmodule
Concedido que los coeficientes son correctos, ¿hay algún problema con el código? Supongo que hay un problema con la representación de los coeficientes en binario, o el multiplicador es incorrecto, pero no puedo resolverlo.