之前探討過PS/2鍵盤編解碼以及數(shù)據(jù)傳輸協(xié)議，這次自己動手實現(xiàn)了利用FPGA接收鍵盤編碼，然后通過串口傳輸?shù)絇C。做的比較簡單，只是通過FPGA把大寫字母A-Z轉(zhuǎn)換成相應(yīng)的ASCII碼，只要字母按鍵被按下，就能在串口調(diào)試助手里顯示相應(yīng)大寫字母。下面就共享代碼吧！
    除了頂層模塊，三個底層模塊分別為PS/2傳輸處理模塊、串口傳輸模塊以及串口波特率選擇模塊（下面只給出頂層模塊和PS/2傳輸處理模塊的verilog代碼）。
module ps2_key(clk,rst_n,ps2k_clk,ps2k_data,rs232_tx);
input clk; //50M時鐘信號
input rst_n;  //復(fù)位信號
input ps2k_clk;   //PS2接口時鐘信號
input ps2k_data;  //PS2接口數(shù)據(jù)信號
output rs232_tx;  // RS232發(fā)送數(shù)據(jù)信號
wire[7:0] ps2_byte;  // 1byte鍵值
wire ps2_state;      //按鍵狀態(tài)標(biāo)志位
wire bps_start;   //接收到數(shù)據(jù)后，波特率時鐘啟動信號置位
wire clk_bps; // clk_bps的高電平為接收或者發(fā)送數(shù)據(jù)位的中間采樣點
ps2scan           ps2scan(   .clk(clk),            //按鍵掃描模塊
                            .rst_n(rst_n),             
                            .ps2k_clk(ps2k_clk),
                            .ps2k_data(ps2k_data),
                             .ps2_byte(ps2_byte),
                            .ps2_state(ps2_state)
                            );
speed_select  speed_select( .clk(clk),
                                   .rst_n(rst_n),
                                   .bps_start(bps_start),
                                   .clk_bps(clk_bps)
                                   );
my_uart_tx    my_uart_tx(       .clk(clk),
                                   .rst_n(rst_n),
                                   .clk_bps(clk_bps),
                                   .rx_data(ps2_byte),
                                   .rx_int(ps2_state),
                                   .rs232_tx(rs232_tx),
                                   .bps_start(bps_start)
                                   );
Endmodule
module ps2scan(clk,rst_n,ps2k_clk,ps2k_data,ps2_byte,ps2_state);
input clk; //50M時鐘信號
input rst_n;  //復(fù)位信號
input ps2k_clk;   //PS2接口時鐘信號
input ps2k_data;  //PS2接口數(shù)據(jù)信號
output[7:0] ps2_byte;    // 1byte鍵值，只做簡單的按鍵掃描
output ps2_state;    //鍵盤當(dāng)前狀態(tài)，ps2_state=1表示有鍵被按下
//------------------------------------------
reg ps2k_clk_r0,ps2k_clk_r1,ps2k_clk_r2;  //ps2k_clk狀態(tài)寄存器
//wire pos_ps2k_clk;     // ps2k_clk上升沿標(biāo)志位
wire neg_ps2k_clk;   // ps2k_clk下降沿標(biāo)志位
always @ (posedge clk or negedge rst_n) begin
    if(!rst_n) begin
           ps2k_clk_r0 <= 1'b0;
           ps2k_clk_r1 <= 1'b0;
           ps2k_clk_r2 <= 1'b0;
       end
    else begin                         //鎖存狀態(tài)，進行濾波
           ps2k_clk_r0 <= ps2k_clk;
           ps2k_clk_r1 <= ps2k_clk_r0;
           ps2k_clk_r2 <= ps2k_clk_r1;
       end
end
assign neg_ps2k_clk = ~ps2k_clk_r1 & ps2k_clk_r2;    //下降沿
//------------------------------------------
reg[7:0] ps2_byte_r;     //PC接收來自PS2的一個字節(jié)數(shù)據(jù)存儲器
reg[7:0] temp_data;  //當(dāng)前接收數(shù)據(jù)寄存器
reg[3:0] num; //計數(shù)寄存器
always @ (posedge clk or negedge rst_n) begin
    if(!rst_n) begin
           num <= 4'd0;
           temp_data <= 8'd0;
       end
    else if(neg_ps2k_clk) begin //檢測到ps2k_clk的下降沿
           case (num)
              4'd0:  num <= num+1'b1;
              4'd1:  begin
                         num <= num+1'b1;
                         temp_data[0] <= ps2k_data;  //bit0
                     end
              4'd2:  begin
                         num <= num+1'b1;
                         temp_data[1] <= ps2k_data;  //bit1
                     end
              4'd3:  begin
                         num <= num+1'b1;
                         temp_data[2] <= ps2k_data;  //bit2
                     end
              4'd4:  begin
                         num <= num+1'b1;
                         temp_data[3] <= ps2k_data;  //bit3
                     end
              4'd5:  begin
                         num <= num+1'b1;
                         temp_data[4] <= ps2k_data;  //bit4
                     end
              4'd6:  begin
                         num <= num+1'b1;
                         temp_data[5] <= ps2k_data;  //bit5
                     end
              4'd7:  begin
                         num <= num+1'b1;
                         temp_data[6] <= ps2k_data;  //bit6
                     end
              4'd8:  begin
                         num <= num+1'b1;
                         temp_data[7] <= ps2k_data;  //bit7
                     end
              4'd9:  begin
                         num <= num+1'b1;  //奇偶校驗位，不做處理
                     end
              4'd10: begin
                         num <= 4'd0;  // num清零
                     end
              default: ;
              endcase
       end
end
reg key_f0;       //松鍵標(biāo)志位，置1表示接收到數(shù)據(jù)8'hf0，再接收到下一個數(shù)據(jù)后清零
reg ps2_state_r;  //鍵盤當(dāng)前狀態(tài)，ps2_state_r=1表示有鍵被按下
always @ (posedge clk or negedge rst_n) begin //接收數(shù)據(jù)的相應(yīng)處理，這里只對1byte的鍵值進行處理
    if(!rst_n) begin
           key_f0 <= 1'b0;
           ps2_state_r <= 1'b0;
       end
    else if(num==4'd10) begin   //剛傳送完一個字節(jié)數(shù)據(jù)
           if(temp_data == 8'hf0) key_f0 <= 1'b1;
           else begin
                  if(!key_f0) begin //說明有鍵按下
                         ps2_state_r <= 1'b1;
                         ps2_byte_r <= temp_data; //鎖存當(dāng)前鍵值
                     end
                  else begin
                         ps2_state_r <= 1'b0;
                         key_f0 <= 1'b0;
                     end
              end
       end
end
reg[7:0] ps2_asci;   //接收數(shù)據(jù)的相應(yīng)ASCII碼
always @ (ps2_byte_r) begin
    case (ps2_byte_r)    //鍵值轉(zhuǎn)換為ASCII碼，這里做的比較簡單，只處理字母
       8'h15: ps2_asci <= 8'h51;   //Q
       8'h1d: ps2_asci <= 8'h57;   //W
       8'h24: ps2_asci <= 8'h45;   //E
       8'h2d: ps2_asci <= 8'h52;   //R
       8'h2c: ps2_asci <= 8'h54;   //T
       8'h35: ps2_asci <= 8'h59;   //Y
       8'h3c: ps2_asci <= 8'h55;   //U
       8'h43: ps2_asci <= 8'h49;   //I
       8'h44: ps2_asci <= 8'h4f;   //O
       8'h4d: ps2_asci <= 8'h50;   //P              
       8'h1c: ps2_asci <= 8'h41;   //A
       8'h1b: ps2_asci <= 8'h53;   //S
       8'h23: ps2_asci <= 8'h44;   //D
       8'h2b: ps2_asci <= 8'h46;   //F
       8'h34: ps2_asci <= 8'h47;   //G
       8'h33: ps2_asci <= 8'h48;   //H
       8'h3b: ps2_asci <= 8'h4a;   //J
       8'h42: ps2_asci <= 8'h4b;   //K
       8'h4b: ps2_asci <= 8'h4c;   //L
       8'h1z: ps2_asci <= 8'h5a;   //Z
       8'h22: ps2_asci <= 8'h58;   //X
       8'h21: ps2_asci <= 8'h43;   //C
       8'h2a: ps2_asci <= 8'h56;   //V
       8'h32: ps2_asci <= 8'h42;   //B
       8'h31: ps2_asci <= 8'h4e;   //N
       8'h3a: ps2_asci <= 8'h4d;   //M
       default: ;
       endcase
end
assign ps2_byte = ps2_asci;
assign ps2_state = ps2_state_r;
endmodule