FPGA（6）电压测量（ADC）_fpga中adc采样参考电压码值怎么写

module  adc8_5v(sys_clk,sys_rst,data8_in,data16_out,adc_clkout,sign,data_medium_out);
 
    input   wire    sys_clk,sys_rst;
    input   wire    [7:0]   data8_in;
output     [7:0]     data_medium_out;
    output  wire     adc_clkout;
    output  wire     [15:0]  data16_out;
    output  wire     sign;
    
    reg     [1:0]   cnt_sysclk;
    reg             adc_clkin;
    reg             adc_en;
    reg     [10:0]   cnt_medium;
    reg     [18:0]   adc_data_sum_medium;
    reg     [7:0]    adc_data_medium;
    reg     [27:0]      volt_reg;
    
    wire        [27:0]  data_PN_p;
    wire        [27:0]  data_PN_n;
parameter   cnt_medium_MAX=1024;
parameter   cnt_mediumBit_MAX=10;
    
    
assign  data_medium_out=data8_in;
//时钟4分频（频率为12.5MHz）（做为AD的驱动时钟）
always@(posedge sys_clk or negedge  sys_rst)
begin
    if(!sys_rst)
    begin
        adc_clkin<=1'b0;
        cnt_sysclk<=2'd0;
    end
    else    if(cnt_sysclk==2'd1)
        begin
            cnt_sysclk<=2'd0;
            adc_clkin<=~adc_clkin;
        end
    else
        begin
            cnt_sysclk<=cnt_sysclk+1'b1;
            adc_clkin<=adc_clkin;
        end
end
//用于产生前期默认的数据(使能采样)
always@(posedge adc_clkin or negedge  sys_rst)
begin
    if(!sys_rst)
        begin
            adc_en<=1'b0;
            cnt_medium<=11'd0;
        end
    else    if(cnt_medium==cnt_medium_MAX)
        begin
            adc_en<=1'b1;
            cnt_medium<=cnt_medium;
        end
    else
        begin
            adc_en<=adc_en;
            cnt_medium<=cnt_medium+1'b1;
        end
end
//用于收集多个接地的基础数据(这里为2^10)
always@(posedge adc_clkin or negedge  sys_rst)
begin
    if(!sys_rst)
        adc_data_sum_medium<=19'd0;
    else    if(cnt_medium==cnt_medium_MAX)
        adc_data_sum_medium<=adc_data_sum_medium;
    else
        adc_data_sum_medium<=adc_data_sum_medium+data8_in;
end
//取平均值
always@(posedge adc_clkin or negedge  sys_rst)
begin
    if(!sys_rst)
        adc_data_medium<=8'd0;
    else    if(cnt_medium==cnt_medium_MAX)
        adc_data_medium<=adc_data_sum_medium>>cnt_mediumBit_MAX;
    else
        adc_data_medium<=adc_data_medium;
end
 
//放大(2^13*1000倍)
assign  data_PN_p=(adc_en==1'b1)? 8192_0000/((255-adc_data_medium)*2):0;
assign  data_PN_n=(adc_en==1'b1)? 8192_0000/((adc_data_medium+1)*2):0;
 
//测量数据放大1000倍
always@(posedge adc_clkin or negedge  sys_rst)
begin
    if(!sys_rst)
        volt_reg<=28'd0;
    else    if(adc_en==1'b1)
        if((data8_in>(adc_data_medium-3))&&(data8_in<(adc_data_medium+3)))
            volt_reg<=28'd0;
    else    if(data8_in<adc_data_medium)
            volt_reg<=(data_PN_n*(adc_data_medium-data8_in))>>13;
    else    if(data8_in>adc_data_medium)
            volt_reg<=(data_PN_p*(data8_in-adc_data_medium))>>13;
    else
            volt_reg<=28'd0;
end
 
//数据在上升沿更新，所以adc驱动程序为下降沿采样数据
assign  adc_clkout=~adc_clkin;
assign  sign=(data8_in<adc_data_medium)? 1'b1:1'b0;
 
 
assign  data16_out=volt_reg;
 
 
endmodule