之前探討過PS/2鍵盤編解碼以及數據傳輸協議，這次自己動手實現了利用FPGA接收鍵盤編碼，然后通過串口傳輸到PC。做的比較簡單，只是通過FPGA把大寫字母A-Z轉換成相應的ASCII碼，只要字母按鍵被按下，就能在串口調試助手里顯示相應大寫字母。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; //復位信號

Input Ps2k_clk; //PS2接口時鐘信號

Input Ps2k_data; //PS2接口數據信號

Output Rs232_tx; // RS232發送數據信號

Wire[7:0] Ps2_byte; // 1byte鍵值

Wire Ps2_state; //按鍵狀態標志位

Wire Bps_start; //接收到數據后，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送數據位的中間采樣點

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; //復位信號

Input Ps2k_clk; //PS2接口時鐘信號

Input Ps2k_data; //PS2接口數據信號

Output[7:0] Ps2_byte; // 1byte鍵值，只做簡單的按鍵掃描

Output Ps2_state; //鍵盤當前狀態，Ps2_state=1表示有鍵被按下

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

Reg Ps2k_clk_r0,Ps2k_clk_r1,Ps2k_clk_r2; //Ps2k_clk狀態寄存器

//Wire Pos_ps2k_clk; // Ps2k_clk上升沿標志位

Wire Neg_ps2k_clk; // Ps2k_clk下降沿標志位

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，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的一個字節數據存儲器

Reg[7:0] Temp_data; //當前接收數據寄存器

Reg[3:0] Num; //計數寄存器

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; //松鍵標志位，置1表示接收到數據8''Hf0，再接收到下一個數據后清零

Reg Ps2_state_r; //鍵盤當前狀態，Ps2_state_r=1表示有鍵被按下

Always @ (Posedge Clk Or Negedge Rst_n) Begin //接收數據的相應處理，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 //剛傳送完一個字節數據

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; //接收數據的相應ASCII碼

Always @ (Ps2_byte_r) Begin

Case (Ps2_byte_r) //鍵值轉換為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: ;