4*4矩阵键盘的FPGA驱动

一、硬件原理

4*4矩阵键盘有4行与4列，在按键按下时一行与一列即导通。其驱动方法非常简单。本设计中以一定的时间频率分别将每一行的引脚电平拉高，并在拉高某个引脚的同时检测每一列的电平变化，当检测到某列引脚有上升沿跳变时，即为该行与该列导通对应的那个按键被按下。
例如上图中，拉高PD4,此时检测到PD2引脚有上升沿电平跳变，则按键S5被按下。其余同理。

二、Verilog代码实现

//////////////////////////////////////////////////////////////////////////////////
// Company: NanJing University of Information Science & Technology
// Engineer: Yang Cheng Yu
// 
// Create Date: 2020/01/13 20:01:50
// Design Name: keyboard_4_4
// Module Name: keyboard_4_4
// Project Name: Clock
// Target Devices: 
// Tool Versions: 
// Description: 
// 
// Dependencies: 
// 
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
// 
//////////////////////////////////////////////////////////////////////////////////
module keyboard_4_4(
	input 					clk,//时钟
	input 					rst,//复位
	output reg[3:0] 		c_pin,//行引脚
	input[3:0] 				r_pin,//列引脚
	output reg[3:0]			key_out//按键编号输出
);
	reg[15:0] 				div_cnt;//分频计数器
	reg[2:0]				state;
	reg						cnt_full;//分频计数器计满逻辑
	localparam				CHECK_R1=3'b000;//检测R1
	localparam				CHECK_R2=3'b001;//检测R2
	localparam				CHECK_R3=3'b011;//检测R3
	localparam				CHECK_R4=3'b010;//检测R4
	//分频计数器逻辑
	[e-mail](posedge clk or negedge rst)begin//此处设计每次拉高一行时间为1ms
		if(!rst)begin
			div_cnt <= 16'd0;
			cnt_full <= 1'b0;
		end
		else
			if(div_cnt==16'd49999)begin
				div_cnt <= 16'd0;
				cnt_full <= 1'b1;
			end
			else begin
				div_cnt <= div_cnt + 1'b1;
				cnt_full <= 1'b0;
			end
	end

	//状态组合判断
	[e-mail](posedge cnt_full or negedge rst)begin
		if(!rst)
			state <= CHECK_R1;
		else
			case(state)
				CHECK_R1:
					if(cnt_full)
						state <= CHECK_R2;
					else
						state <= CHECK_R1;
				CHECK_R2:
					if(cnt_full)
						state <= CHECK_R3;
					else
						state <= CHECK_R2;
				CHECK_R3:
					if(cnt_full)
						state <= CHECK_R4;
					else
						state <= CHECK_R3;
				CHECK_R4:
					if(cnt_full)
						state <= CHECK_R1;
					else
						state <= CHECK_R4;
				default:
					state <= state;
			endcase
	end
	//状态机输出逻辑
	[e-mail](posedge clk or negedge rst)begin
		if(!rst)
			c_pin <= 4'b0000;
		else
			case(state)
				CHECK_R1:begin
					c_pin <= 4'b1000;
					case(r_pin)
						4'b1000:key_out <= 4'd0;
						4'b0100:key_out <= 4'd1;
						4'b0010:key_out <= 4'd2;
						4'b0001:key_out <= 4'd3;
					endcase
				end
				CHECK_R2:begin
					c_pin <= 4'b0100;
					case(r_pin)
						4'b1000:key_out <= 4'd4;
						4'b0100:key_out <= 4'd5;
						4'b0010:key_out <= 4'd6;
						4'b0001:key_out <= 4'd7;
					endcase
				end
				CHECK_R3:begin
					c_pin <= 4'b0010;
					case(r_pin)
						4'b1000:key_out <= 4'd8;
						4'b0100:key_out <= 4'd9;
						4'b0010:key_out <= 4'd10;
						4'b0001:key_out <= 4'd11;
					endcase
				end
				CHECK_R4:begin
					c_pin <= 4'b0001;
					case(r_pin)
						4'b1000:key_out <= 4'd12;
						4'b0100:key_out <= 4'd13;
						4'b0010:key_out <= 4'd14;
						4'b0001:key_out <= 4'd15;
					endcase
				end	
				default:begin
					c_pin <= 4'b0000;
					key_out <= 4'd0;
				end
			endcase
	end
endmodule

状态转移图