9.1 4*4矩阵键盘驱动

1. 4*4键盘的结构为4行4列，共16个交叉点，代表16个按键，行编号为A，列编号为B。按下某键后，辨别和读取键值一般采用如下方法：

    向A端口扫描输入一组只含有一个0的4位数据，若有按键按下，B端口会输出相应的数据，然后结合A、B端口的数据，判断按键的位置。

2. 整个键盘扫描检测，设计思想还是编码译码。扫描时钟用1KHz，用一个模4的计数器，每个计数值对应一行，编码A。组合读入的列编码，

   根据查找表，就很容易确定按键位置，按键值。

3. 4*4矩阵键盘扫描检测程序：

/*4*4 keyboard scan and display */
//2020-11-04
//by YongFengXie
module key4x4(rst,clk50M,a,b,led7s);
input clk50M;   //keyboard scan clock 
input rst;
input [3:0] b;
output reg [3:0] a; // output scan signal to keyboard
output reg [6:0] led7s;
reg [3:0] keyvalue;
reg [1:0] q;        //counter 4
reg clk;            // 1KHz
reg [14:0] count;   //div counter,50M to 1K

always @(posedge rst or posedge clk50M)
// 50M divide 25 000 to 1K Hz
begin
  if(rst)
  begin
    clk <= 0;
    count <= 0;
    q<=0;
  end
  else if(count == 25000)
  begin
    count <= 0;
    clk <= ~clk;
  end
  else
    count <= count + 1;
end

always @(posedge clk)
begin
  q <= q+1;
  case(q)     // send data to keyboard A port
    0: a<=4'b1110;
    1: a<=4'b1101;
    2: a<=4'b1011;
    3: a<=4'b0111;
    default: a<=4'b0000;
  endcase
  case({a,b})  // judge keyvalue
    8'b1110_0111: begin keyvalue<=4'b0000;
                        led7s<=7'b1000000;
                  end  // key0
    8'b1110_1011: begin keyvalue<=4'b0001;
                        led7s<=7'b1111001;
                  end  // key1     
    8'b1110_1101: begin keyvalue<=4'b0010;
                        led7s<=7'b0100100;
                  end  // key2
    8'b1110_1110: begin keyvalue<=4'b0011;
                        led7s<=7'b0110000;
                  end  // key3                 
    8'b1101_0111: begin keyvalue<=4'b0100;
                        led7s<=7'b0011001;
                  end  // key4
    8'b1101_1011: begin keyvalue<=4'b0101;
                        led7s<=7'b0010010;
                  end  // key5     
    8'b1101_1101: begin keyvalue<=4'b0110;
                        led7s<=7'b0000010;
                  end  // key6
    8'b1101_1110: begin keyvalue<=4'b0111;
                        led7s<=7'b1111000;
                  end  // key7 
    8'b1011_0111: begin keyvalue<=4'b1000;
                        led7s<=7'b0000000;
                  end  // key8
    8'b1011_1011: begin keyvalue<=4'b1001;
                        led7s<=7'b0010000;
                  end  // key9     
    8'b1011_1101: begin keyvalue<=4'b1010;
                        led7s<=7'b0001000;
                  end  // keyA
    8'b1011_1110: begin keyvalue<=4'b1011;
                        led7s<=7'b0000011;
                  end  // keyB
    8'b0111_0111: begin keyvalue<=4'b1100;
                        led7s<=7'b1000110;
                  end  // keyC
    8'b0111_1011: begin keyvalue<=4'b1101;
                        led7s<=7'b0100001;
                  end  // keyD     
    8'b1110_1101: begin keyvalue<=4'b1110;
                        led7s<=7'b0000110;
                  end  // keyE
    8'b0111_1110: begin keyvalue<=4'b1111;
                        led7s<=7'b0001110;
                  end  // keyF 
    default:begin keyvalue<=4'b0000;led7s<=7'b1111111;end
  endcase
end

endmodule


    

测试代码：

/*4*4 keyboard scan and display testbench */
//2020-11-04
//by YongFengXie
`timescale 10ns/1ns
module key4x4_tb;
reg clk50M;   //keyboard scan clock 
reg rst;
reg [3:0] b;
wire [3:0] a; // output scan signal to keyboard
wire [6:0] led7s;

key4x4 ub(rst,clk50M,a,b,led7s);

initial begin
          clk50M=0;
          rst=1;
          b=4'b0000;
          #2 rst=0;
          #1600000 $stop;
        end

always #1 clk50M=~clk50M;

initial begin #100000 b=4'b0111;
              #100000 b=4'b1011;
              #100000 b=4'b1101;
              #100000 b=4'b1110;
        end

endmodule

仿真结果：

4. 总结：

    参照王金明的设计，其实还是有很多问题：1。矩阵键盘需要淘；2。仿真因为包含分频，所以测试模块还不完善，16个按键，16种组合，每种持续时长都是需要考虑。