module FM_Demodulation (
    input             EOC                      ,
    input      [ 2:0] Channel                  ,
    input      [ 3:0] FM_HW_state              ,
    input             RSTn                     ,
    input      [11:0] ADC_Data                 ,
    input             demod_en                 ,
    output reg [ 9:0] demodulated_signal_sample,
    output            clk_fm_demo_sampling
);

// workable filter, filtering audio data:
    parameter fir_0  = 8'h11 ;
    parameter fir_1  = 8'h22 ;
    parameter fir_2  = 8'h39 ;
    parameter fir_3  = 8'h55 ;
    parameter fir_4  = 8'h76 ;
    parameter fir_5  = 8'h98 ;
    parameter fir_6  = 8'hb9 ;
    parameter fir_7  = 8'hd7 ;
    parameter fir_8  = 8'hef ;
    parameter fir_9  = 9'hfe ;
    parameter fir_10 = 9'h103;
    parameter fir_11 = 8'hfe ;
    parameter fir_12 = 8'hef ;
    parameter fir_13 = 8'hd7 ;
    parameter fir_14 = 8'hb9 ;
    parameter fir_15 = 8'h98 ;
    parameter fir_16 = 8'h76 ;
    parameter fir_17 = 8'h55 ;
    parameter fir_18 = 8'h39 ;
    parameter fir_19 = 8'h22 ;
    parameter fir_20 = 8'h11 ;

    reg [ 7:0] IdataN_1                = 8'h0 ;
    reg [ 7:0] IdataN                  = 8'h0 ;
    reg [ 7:0] QdataN_1                = 8'h0 ;
    reg [ 7:0] QdataN                  = 8'h0 ;
    reg        EOC_Count_Demodulate    = 1'b0 ;
    reg [16:0] demodulated_signal_temp = 17'h0;


    reg [ 9:0] dmd_data_filter  [20:0];
    reg [23:0] dmd_data_filtered      ;

    integer ii;

    initial begin
        for(ii=0;ii<5'd21;ii=ii+1) begin
            dmd_data_filter[ii]=10'b0;
        end
    end

    always@(posedge EOC) begin
        if(FM_HW_state == 4'b0010) begin //normal FM receiver
            if(Channel==3'b110) begin     //CH6 is the I Path
                IdataN   <= IdataN_1;
                IdataN_1 <= ADC_Data[11:4];
            end
            if(Channel==3'b100) begin     //CH4 is the Q Path
                QdataN   <= QdataN_1;
                QdataN_1 <= ADC_Data[11:4];
            end
        end
    end



    always@(posedge EOC) begin
        if(FM_HW_state == 4'b0010) begin //normal FM receiver
            if(EOC_Count_Demodulate == 1'b0)
                EOC_Count_Demodulate <= 1'b1;
            else EOC_Count_Demodulate<=1'b0;
        end
    end

    always@(posedge EOC_Count_Demodulate  or negedge RSTn ) begin
        if(~RSTn)
            demodulated_signal_temp <= 17'h0;
        else demodulated_signal_temp <=((IdataN*QdataN_1+17'h10000) - QdataN*IdataN_1);
    end

//filtering

    always@(posedge EOC_Count_Demodulate  or negedge RSTn ) begin
        if(~RSTn)
            dmd_data_filtered <= 24'h0;
        else begin
            dmd_data_filter[20] <= demodulated_signal_temp[16:7];
            dmd_data_filter[19] <= dmd_data_filter[20];
            dmd_data_filter[18] <= dmd_data_filter[19];
            dmd_data_filter[17] <= dmd_data_filter[18];
            dmd_data_filter[16] <= dmd_data_filter[17];
            dmd_data_filter[15] <= dmd_data_filter[16];
            dmd_data_filter[14] <= dmd_data_filter[15];
            dmd_data_filter[13] <= dmd_data_filter[14];
            dmd_data_filter[12] <= dmd_data_filter[13];
            dmd_data_filter[11] <= dmd_data_filter[12];
            dmd_data_filter[10] <= dmd_data_filter[11];
            dmd_data_filter[9]  <= dmd_data_filter[10];
            dmd_data_filter[8]  <= dmd_data_filter[9];
            dmd_data_filter[7]  <= dmd_data_filter[8];
            dmd_data_filter[6]  <= dmd_data_filter[7];
            dmd_data_filter[5]  <= dmd_data_filter[6];
            dmd_data_filter[4]  <= dmd_data_filter[5];
            dmd_data_filter[3]  <= dmd_data_filter[4];
            dmd_data_filter[2]  <= dmd_data_filter[3];
            dmd_data_filter[1]  <= dmd_data_filter[2];
            dmd_data_filter[0]  <= dmd_data_filter[1];

            dmd_data_filtered <= dmd_data_filter[20]*fir_0 + dmd_data_filter[19]*fir_1 + dmd_data_filter[18]*fir_2 +
                dmd_data_filter[17]*fir_3 + dmd_data_filter[16]*fir_4 + dmd_data_filter[15]*fir_5 +
                dmd_data_filter[14]*fir_6 + dmd_data_filter[13]*fir_7 + dmd_data_filter[12]*fir_8 +
                dmd_data_filter[11]*fir_9 + dmd_data_filter[10]*fir_10 + dmd_data_filter[9]*fir_11 +
                dmd_data_filter[8]*fir_12 + dmd_data_filter[7]*fir_13 + dmd_data_filter[6]*fir_14 +
                dmd_data_filter[5]*fir_15 + dmd_data_filter[4]*fir_16 + dmd_data_filter[3]*fir_17 +
                dmd_data_filter[2]*fir_18 + dmd_data_filter[1]*fir_19 + dmd_data_filter[0]*fir_20;
            /*
            dmd_data_filtered <= (32768+dmd_data_filter[19]*fir_1 + dmd_data_filter[18]*fir_2 +
            dmd_data_filter[17]*fir_3 + dmd_data_filter[13]*fir_7 + dmd_data_filter[12]*fir_8 +
            dmd_data_filter[11]*fir_9 + dmd_data_filter[10]*fir_10 + dmd_data_filter[9]*fir_11 +
            dmd_data_filter[8]*fir_12 + dmd_data_filter[7]*fir_13 + dmd_data_filter[3]*fir_17 +
            dmd_data_filter[2]*fir_18 + dmd_data_filter[1]*fir_19)  -
            (dmd_data_filter[20]*fir_0 +dmd_data_filter[16]*fir_4 + dmd_data_filter[15]*fir_5 +
            dmd_data_filter[14]*fir_6 + dmd_data_filter[6]*fir_14 + dmd_data_filter[5]*fir_15 +
            dmd_data_filter[4]*fir_16 + dmd_data_filter[0]*fir_20);
            */
        end

    end


    clk_fm_demo_sample_pwm fm_sample (
        .FM_demod_en         (demod_en            ),
        .EOC                 (EOC                 ),
        .RSTn                (RSTn                ),
        .clk_fm_demo_sampling(clk_fm_demo_sampling)
    );


//downsampling
    always@(posedge clk_fm_demo_sampling  or negedge RSTn  ) begin
        if(~RSTn)
            demodulated_signal_sample <= 10'h0;
        else begin             //normal FM receiver
            demodulated_signal_sample[9:0] <= dmd_data_filtered[22:13];
        end
    end


endmodule