基于Xilinx FPGA的通用信号采集器

上一篇写了基于Xilinx FPGA的通用信号发生器的案例，反响比较好，很多朋友和我探讨相关的技术，其中就涉及到信号的采集，为了使该文更有血有肉，我在写一篇基于Xilinx FPGA的通用信号采集器，望能形成呼应，以解答大家的疑问。目的：1.通过设计实现信号采集与分析，掌握组合逻辑设计方法；2.通过设计实现信号的采集与分析，掌握信号采集原理。原理：利用FPGA芯片，用verilog语言编写逻辑，控制AD0809进行AD转换。AD0809是带有8位AD转换器、8路多路开关以及微处理机兼容的控制逻辑的CMOS组件，它是逐次逼近式的AD转换器。AD0809的内部结构图如下：

由上图可知，多路开关可选通8 个模拟通道，允许8路模拟量分时输入，共用AD转换器进行转换，三态输出锁存器用于锁存AD转换完成后的数字量，当OE为高时才可以从锁存器取出转换后的数据。通道选择如下图所示：

START为转换启动信号。当START上跳沿时，所有内部寄存器清零；下跳沿时，开始进行A/D 转换；在转换期间，START应保持低电平。EOC 为转换结束信号。当EOC 为高电平时，表明转换结束；否则，表明正在进行A/D 转换。OE为输出允许信号，用于控制三条输出锁存器向单片机输出转换得到的数据。OE＝1，输出转换得到的数据；OE＝0，输出数据线呈高阻状态。时序如下图所示：

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254源代码1.Verilog源代码，dataCollect.vmodule dataCollect(sysclk, rst, adda, addb, addc, start, oe,         datain, led_sel, led_seg);    input sysclk, rst;    input wire [7:0] datain;    output reg adda, addb, addc, start, oe;    output reg[3:0] led_sel;    output reg[7:0] led_seg;     reg [3:0] counter1;    reg [7:0] readdata;     reg [9:0] counter2;    reg [15:0] sum;    reg [7:0] averdata;     reg [7:0] temp;    reg [3:0] dataout1, dataout2, dataout3;     reg [3:0] counter3;     parameter ZERO = 8'b11111100,ONE = 8'b01100000, TWO = 8'b11011010;    parameter THREE = 8'b11110010, FOUR =8'b01100110;    parameter FIVE = 8'b10110110, SIX = 8'b10111110, SEVEN =8'b11100000;    parameter EIGHT = 8'b11111110, NINE = 8'b11110110, BLANK = 8'b00000000;      always @(posedge sysclk or negedge rst)    begin        if (!rst)        begin            adda = 0;            addb = 0;            addc = 0;             oe = 1;             counter1 = 0;        end        else        begin            counter1 = counter1 + 1;            case (counter1)                3 : start = 0;                4 : start = 1;                5 : start = 0;                10 : readdata = datain;                15 : counter1 = 0;                default : counter1 = counter1;            endcase        end    end     always @(posedge sysclk or negedge rst)    begin        if (!rst)        begin            counter2 = 0;            sum = 0;            averdata = 0;        end        else        begin            counter2 = counter2 + 1;            if ((counter2%16) == 0)                sum = sum + readdata;            else if (counter2 > 512)            begin                averdata = sum / 32;                sum