之前探讨过PS/2键盘编解码以及数据传输协议，这次自己动手实现了利用FPGA接收键盘编码，然后通过串口传输到PC。做的比较简单，只是通过FPGA把大写字母A-Z转换成相应的ASCII码，只要字母按键被按下，就能在串口调试助手里显示相应大写字母。下面就共享代码吧！

除了顶层模块，三个底层模块分别为PS/2传输处理模块、串口传输模块以及串口波特率选择模块（下面只给出顶层模块和PS/2传输处理模块的verilog代码）。

module ps2_key(clk,rst_n,ps2k_clk,ps2k_data,rs232_tx);

input clk; //50M时钟信号

input rst_n;//复位信号

input ps2k_clk;//PS2接口时钟信号

input ps2k_data;//PS2接口数据信号

output rs232_tx;// RS232发送数据信号

wire[7:0] ps2_byte;// 1byte键值

wire ps2_state;//按键状态标志位

wire bps_start;//接收到数据后，波特率时钟启动信号置位

wire clk_bps; // clk_bps的高电平为接收或者发送数据位的中间采样点

ps2scanps2scan(.clk(clk),//按键扫描模块

.rst_n(rst_n),

.ps2k_clk(ps2k_clk),

.ps2k_data(ps2k_data),

.ps2_byte(ps2_byte),

.ps2_state(ps2_state)

);

speed_selectspeed_select( .clk(clk),

.rst_n(rst_n),

.bps_start(bps_start),

.clk_bps(clk_bps)

);

my_uart_txmy_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时钟信号

input rst_n;//复位信号

input ps2k_clk;//PS2接口时钟信号

input ps2k_data;//PS2接口数据信号

output[7:0] ps2_byte;// 1byte键值，只做简单的按键扫描

output ps2_state;//键盘当前状态，ps2_state=1表示有键被按下

//------------------------------------------

reg ps2k_clk_r0,ps2k_clk_r1,ps2k_clk_r2;//ps2k_clk状态寄存器

//wire pos_ps2k_clk;// ps2k_clk上升沿标志位

wire neg_ps2k_clk;// ps2k_clk下降沿标志位

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//锁存状态，进行滤波

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接收来自PS2的一个字节数据存储器

reg[7:0] temp_data;//当前接收数据寄存器

reg[3:0] num; //计数寄存器

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 //检测到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;//奇偶校验位，不做处理

end

4'd10: begin

num <= 4'd0;// num清零

end

default: ;

endcase

end

end

reg key_f0;//松键标志位，置1表示接收到数据8'hf0，再接收到下一个数据后清零

reg ps2_state_r;//键盘当前状态，ps2_state_r=1表示有键被按下

always @ (posedge clk or negedge rst_n) begin //接收数据的相应处理，这里只对1byte的键值进行处理

if(!rst_n) begin

key_f0 <= 1'b0;

ps2_state_r <= 1'b0;

end

else if(num==4'd10) begin//刚传送完一个字节数据

if(temp_data == 8'hf0) key_f0 <= 1'b1;

else begin

if(!key_f0) begin //说明有键按下

ps2_state_r <= 1'b1;

ps2_byte_r <= temp_data; //锁存当前键值

end

else begin

ps2_state_r <= 1'b0;

key_f0 <= 1'b0;

end

end

end

end

reg[7:0] ps2_asci;//接收数据的相应ASCII码

always @ (ps2_byte_r) begin

case (ps2_byte_r)//键值转换为ASCII码，这里做的比较简单，只处理字母

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