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--- fpga16_instrument [2021/02/23 16:35]
gongyusu
+++ fpga16_instrument [2021/03/08 17:38] (当前版本)
gongyusu [OLED显示及按键控制]
@@ 行 2: / 行 2: @@
 {{ :fpga16dds1.jpg |口袋仪器的3D效果图}} <WRAP centeralign> 口袋仪器的3D效果图</WRAP>
-### 主要功能
+### 板上功能介绍
 它的核心是一个基于Lattice的XO2、自带下载器的FPGA最小系统模块，做了一个简单的扩展板，主要支持以下的功能：
   - 输入/输出：
@@ 行 24: / 行 24: @@
 因此在实际的使用中，我们一般避免将占空比用到0%或100%，比如可以从10% - 90%之间变化，经过低通滤波器平滑输出后的直流在3.3*10% ~ 3.3 * 90% - 0.33V - 2.97V
-#### DDS+PWM产生任意波形
+在生成PWM的波形的时候要充分理解PWM的时序关系，见下图：
-{{ :fpga_pwm_awg.jpg |}} <WRAP centeralign> 任意波形发生器模拟电路部分原理图 </WRAP>
+{{ :pwm_timing.png |}}<WRAP centeralign> PWM的时序关系 </WRAP>
-通过调节PWM的占空比（0.5/3.3 ~ 3/3.3）得到等效幅度为0.5V - 3V之间的模拟信号，幅度变化的范围为2.5V，要得到幅度为5Vpp的模拟信号，则放大器的增益设定为G = 2：
-也就是在电路原理图中放大器的增益为：R14/(R6+R7+R2) = 2
-取R14 = 4.3K，则R6+R7+R2 = 2.15K
-PWM波形的中间值为（0.5+3.0）/2 = 1.75V，因此：
-  - 在PWM的输出为1.75V的时候，运算放大器的输出应为0V
-  - PWM的输出为0.5V的时候，运算放大器的输出为2.5V
-  - PWM的输出为3V的时候，运算放大器的输出为-2.5V
-由此直流偏移的要求可以得到R10 + R13 = 6.5V
+t为生成PWM信号的主时钟，通过对这个高频时钟计数，得到一个周期T内电平进行0、1反转的脉宽不同的信号。一个T内有多少个t，也就决定了PWM的分辨率，转换到模拟信号的时候也就对应于DAC的位数。根据最高频率/分辨率，也就可以推算出T的最小值。
-同时R6、C6，R7、C7以及R14、C11共同构成低通滤波器。
+比如采用12MHz（t=83ns）的时钟作为PWM的主时钟，如果要生成8位精度的DAC，对应的一个PWM周期T ～ 12MHz/256 = 21μs，最高的频率为47KHz
+如果通过FPGA内部PLL产生高倍频的时钟，比如12M * 16 ～ 192MHz，生成8位精度的DAC，其最高频率可以达到47KHz * 16
+同样192MHz的主时钟来产生12位精度的DAC，则能够生成PWM信号的频率为47KHz
+### OLED显示及按键控制
+本平台采用了128*64分辨率的OLED显示屏，并有4个按键进行参数的设置或菜单的控制，这些按键的功能可以根据自己的需要进行定制。
-{{ :undefined:fpgascope_simulation.jpg |}} <WRAP centeralign> 任意波形发生器模拟电路部分的仿真 </WRAP>
+下面的代码完成了OLED显示屏的驱动，并在屏幕上显示一些与口袋仪器相关的参数，4个按键的扫描控制功能也一并包含在内。
+<code verilog>
+// --------------------------------------------------------------------
+// >>>>>>>>>>>>>>>>>>>>>>>>> COPYRIGHT NOTICE <<<<<<<<<<<<<<<<<<<<<<<<<
+// --------------------------------------------------------------------
+// Module: OLED12832
+//
+// Author: Step
+//
+// Description: OLED12832_Driver
+//
+// Web: www.stepfpga.com
+//
+// --------------------------------------------------------------------
+// Code Revision History :
+// --------------------------------------------------------------------
+// Version: |Mod. Date:   |Changes Made:
+// V1.0     |2015/11/11   |Initial ver
+// --------------------------------------------------------------------
+module OLED12832
+(
+	input clk,	//
+	input rst_n,	//
+	input [3:0]  sw,// 4 push buttons as control input
+	input [7:0]  freq_100,
+	input [7:0]  freq_10,
+	input [7:0]  freq_1,
+	input [7:0]  dc1_10,
+	input [7:0]  dc1_1,
+	input [7:0]  dc1_01,
+	input [7:0]  dc2_10,
+	input [7:0]  dc2_1,
+	input [7:0]  dc2_01,
+	output	reg oled_csn,	//
+	output	reg oled_rst,	//
+	output	reg oled_dcn,	//
+	output	reg oled_clk,	//
+	output	reg oled_dat
+);
+	localparam INIT_DEPTH = 16'd28; //
+	localparam IDLE = 6'h1, MAIN = 6'h2, INIT = 6'h4, SCAN = 6'h8, WRITE = 6'h10, DELAY = 6'h20;
+	localparam HIGH	= 1'b1, LOW = 1'b0;
+	localparam DATA	= 1'b1, CMD = 1'b0;
+	reg [7:0] cmd [27:0];
+	reg [39:0] mem [122:0];
+	reg [7:0] y_p, x_ph, x_pl;
+	reg [(8*21-1):0] char;
+	reg [7:0] num, char_reg;				//
+	reg [4:0] cnt_main, cnt_init, cnt_scan, cnt_write;
+	reg [15:0] num_delay, cnt_delay, cnt;
+	reg [5:0] state, state_back;
+	always@(posedge clk or negedge rst_n) begin
+		if(!rst_n) begin
+			cnt_main <= 1'b0; cnt_init <= 1'b0; cnt_scan <= 1'b0; cnt_write <= 1'b0;
+			y_p <= 1'b0; x_ph <= 1'b0; x_pl <= 1'b0;
+			num <= 1'b0; char <= 1'b0; char_reg <= 1'b0;
+			num_delay <= 16'd5; cnt_delay <= 1'b0; cnt <= 1'b0;
+			oled_csn <= HIGH; oled_rst <= HIGH; oled_dcn <= CMD; oled_clk <= HIGH; oled_dat <= LOW;
+			state <= IDLE; state_back <= IDLE;
+		end else begin
+			case(state)
+				IDLE:begin
+						cnt_main <= 1'b0; cnt_init <= 1'b0; cnt_scan <= 1'b0; cnt_write <= 1'b0;
+						y_p <= 1'b0; x_ph <= 1'b0; x_pl <= 1'b0;
+						num <= 1'b0; char <= 1'b0; char_reg <= 1'b0;
+						num_delay <= 16'd5; cnt_delay <= 1'b0; cnt <= 1'b0;
+						oled_csn <= HIGH; oled_rst <= HIGH; oled_dcn <= CMD; oled_clk <= HIGH; oled_dat <= LOW;
+						state <= MAIN; state_back <= MAIN;
+					end
+				MAIN:begin
+						if(cnt_main >= 5'd16) cnt_main <= 5'd9;
+						else cnt_main <= cnt_main + 1'b1;
+						case(cnt_main)	//MAIN状态
+'d0:	begin state <= INIT; end
+'d1:	begin y_p <= 8'hb0; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd16; char <= "----------------";state <= SCAN; end
+'d2:	begin y_p <= 8'hb1; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd16; char <= " FPGA Training  ";state <= SCAN; end
+'d3:	begin y_p <= 8'hb2; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd16; char <= " www.eetree.cn  ";state <= SCAN; end
+'d4:	begin y_p <= 8'hb3; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd16; char <= "----------------";state <= SCAN; end
+'d5:	begin y_p <= 8'hb4; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd16; char <= "                 ";state <= SCAN; end
+'d6:	begin y_p <= 8'hb5; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd16; char <= "                 ";state <= SCAN; end
+'d7:	begin y_p <= 8'hb6; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd16; char <= "                 ";state <= SCAN; end
+'d8:	begin y_p <= 8'hb7; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd16; char <= "                ";state <= SCAN; end
+'d9:	begin y_p <= 8'hb4; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd13; char <= {"I-->W,DC-1KHz"} ;state <= SCAN; end
+'d10:	begin y_p <= 8'hb5; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd10; char <= {"DC1: +3.0V"}   ;state <= SCAN; end
+'d11:	begin y_p <= 8'hb6; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd10; char <= {"DC2: -3.0V"}   ;state <= SCAN; end
+'d12:	begin y_p <= 8'hb7; x_ph <= 8'h10; x_pl <= 8'h00; num <= 5'd12; char <= {"Have Fun! :)" };state <= SCAN; end
+'d13:	begin y_p <= 8'hb4; x_ph <= 8'h17; x_pl <= 8'h08; num <= 5'd 1; char <= sw; state <= SCAN; end
+'d14:	begin y_p <= 8'hb5; x_ph <= 8'h17; x_pl <= 8'h08; num <= 5'd 1; char <= sw; state <= SCAN; end
+'d15:	begin y_p <= 8'hb6; x_ph <= 8'h17; x_pl <= 8'h08; num <= 5'd 1; char <= sw; state <= SCAN; end
+'d16:	begin y_p <= 8'hb7; x_ph <= 8'h17; x_pl <= 8'h08; num <= 5'd 1; char <= sw; state <= SCAN; end
-#### 产生可调电压
+							default: state <= IDLE;
-{{ :fpga_pwm_dc.jpg |}}<WRAP centeralign> 通过PWM产生可变直流电压的模拟电路原理图 </WRAP>
+						endcase
+					end
+				INIT:begin	//
+						case(cnt_init)
+'d0:	begin oled_rst <= LOW; cnt_init <= cnt_init + 1'b1; end	//
+'d1:	begin num_delay <= 16'd25000; state <= DELAY; state_back <= INIT; cnt_init <= cnt_init + 1'b1; end	//
+'d2:	begin oled_rst <= HIGH; cnt_init <= cnt_init + 1'b1; end	//
+'d3:	begin num_delay <= 16'd25000; state <= DELAY; state_back <= INIT; cnt_init <= cnt_init + 1'b1; end	//
+'d4:	begin
+										if(cnt>=INIT_DEPTH) begin	//
+											cnt <= 1'b0;
+											cnt_init <= cnt_init + 1'b1;
+										end else begin
+											cnt <= cnt + 1'b1; num_delay <= 16'd5;
+											oled_dcn <= CMD; char_reg <= cmd[cnt]; state <= WRITE; state_back <= INIT;
+										end
+									end
+'d5:	begin cnt_init <= 1'b0; state <= MAIN; end	//
+							default: state <= IDLE;
+						endcase
+					end
+				SCAN:begin	//
+						if(cnt_scan == 5'd11) begin
+							if(num) cnt_scan <= 5'd3;
+							else cnt_scan <= cnt_scan + 1'b1;
+						end else if(cnt_scan == 5'd12) cnt_scan <= 1'b0;
+						else cnt_scan <= cnt_scan + 1'b1;
+						case(cnt_scan)
+'d 0:	begin oled_dcn <= CMD; char_reg <= y_p; state <= WRITE; state_back <= SCAN; end		//
+'d 1:	begin oled_dcn <= CMD; char_reg <= x_pl; state <= WRITE; state_back <= SCAN; end	//
+'d 2:	begin oled_dcn <= CMD; char_reg <= x_ph; state <= WRITE; state_back <= SCAN; end	//
+'d 3:	begin num <= num - 1'b1;end
+'d 4:	begin oled_dcn <= DATA; char_reg <= 8'h00; state <= WRITE; state_back <= SCAN; end	//
+'d 5:	begin oled_dcn <= DATA; char_reg <= 8'h00; state <= WRITE; state_back <= SCAN; end	//
+'d 6:	begin oled_dcn <= DATA; char_reg <= 8'h00; state <= WRITE; state_back <= SCAN; end	//
+'d 7:	begin oled_dcn <= DATA; char_reg <= mem[char[(num*8)+:8]][39:32]; state <= WRITE; state_back <= SCAN; end
+'d 8:	begin oled_dcn <= DATA; char_reg <= mem[char[(num*8)+:8]][31:24]; state <= WRITE; state_back <= SCAN; end
+'d 9:	begin oled_dcn <= DATA; char_reg <= mem[char[(num*8)+:8]][23:16]; state <= WRITE; state_back <= SCAN; end
+'d10:	begin oled_dcn <= DATA; char_reg <= mem[char[(num*8)+:8]][15: 8]; state <= WRITE; state_back <= SCAN; end
+'d11:	begin oled_dcn <= DATA; char_reg <= mem[char[(num*8)+:8]][ 7: 0]; state <= WRITE; state_back <= SCAN; end
+'d12:	begin state <= MAIN; end
+							default: state <= IDLE;
+						endcase
+					end
+				WRITE:begin	//
+						if(cnt_write >= 5'd17) cnt_write <= 1'b0;
+						else cnt_write <= cnt_write + 1'b1;
+						case(cnt_write)
+'d 0:	begin oled_csn <= LOW; end	//
+'d 1:	begin oled_clk <= LOW; oled_dat <= char_reg[7]; end	//
+'d 2:	begin oled_clk <= HIGH; end
+'d 3:	begin oled_clk <= LOW; oled_dat <= char_reg[6]; end
+'d 4:	begin oled_clk <= HIGH; end
+'d 5:	begin oled_clk <= LOW; oled_dat <= char_reg[5]; end
+'d 6:	begin oled_clk <= HIGH; end
+'d 7:	begin oled_clk <= LOW; oled_dat <= char_reg[4]; end
+'d 8:	begin oled_clk <= HIGH; end
+'d 9:	begin oled_clk <= LOW; oled_dat <= char_reg[3]; end
+'d10:	begin oled_clk <= HIGH; end
+'d11:	begin oled_clk <= LOW; oled_dat <= char_reg[2]; end
+'d12:	begin oled_clk <= HIGH; end
+'d13:	begin oled_clk <= LOW; oled_dat <= char_reg[1]; end
+'d14:	begin oled_clk <= HIGH; end
+'d15:	begin oled_clk <= LOW; oled_dat <= char_reg[0]; end	//
+'d16:	begin oled_clk <= HIGH; end
+'d17:	begin oled_csn <= HIGH; state <= DELAY; end	//
+							default: state <= IDLE;
+						endcase
+					end
+				DELAY:begin	//
+						if(cnt_delay >= num_delay) begin
+							cnt_delay <= 16'd0; state <= state_back;
+						end else cnt_delay <= cnt_delay + 1'b1;
+					end
+				default:state <= IDLE;
+			endcase
+		end
+	end
+	//
+	always@(negedge rst_n)
-#### 通过高速比较器实现ADC的功能
+		begin
+			cmd[ 0] = {8'hae};
+			cmd[ 1] = {8'h00};
+			cmd[ 2] = {8'h10};
+			cmd[ 3] = {8'h40};
+			cmd[ 4] = {8'h81};
+			cmd[ 5] = {8'hcf};
+			cmd[ 6] = {8'ha1};
+			cmd[ 7] = {8'hc8};
+			cmd[ 8] = {8'ha6};
+			cmd[ 9] = {8'ha8};
+			cmd[10] = {8'h3f};
+			cmd[11] = {8'hd3};
+			cmd[12] = {8'h00};
+			cmd[13] = {8'hd5};
+			cmd[14] = {8'h80};
+			cmd[15] = {8'hd9};
+			cmd[16] = {8'hf1};
+			cmd[17] = {8'hda};
+			cmd[18] = {8'h12};
+			cmd[19] = {8'hdb};
+			cmd[20] = {8'h40};
+			cmd[21] = {8'h20};
+			cmd[22] = {8'h02};
+            cmd[23] = {8'h8d};
+			cmd[24] = {8'h14};
+            cmd[25] = {8'ha4};
+            cmd[26] = {8'ha6};
+			cmd[27] = {8'haf};
+		end
+	always@(negedge rst_n)
+	//initial
+		begin
+			mem[  0] = {8'h3E, 8'h51, 8'h49, 8'h45, 8'h3E};   // 48  0
+			mem[  1] = {8'h00, 8'h42, 8'h7F, 8'h40, 8'h00};   // 49  1
+			mem[  2] = {8'h42, 8'h61, 8'h51, 8'h49, 8'h46};   // 50  2
+			mem[  3] = {8'h21, 8'h41, 8'h45, 8'h4B, 8'h31};   // 51  3
+			mem[  4] = {8'h18, 8'h14, 8'h12, 8'h7F, 8'h10};   // 52  4
+			mem[  5] = {8'h27, 8'h45, 8'h45, 8'h45, 8'h39};   // 53  5
+			mem[  6] = {8'h3C, 8'h4A, 8'h49, 8'h49, 8'h30};   // 54  6
+			mem[  7] = {8'h01, 8'h71, 8'h09, 8'h05, 8'h03};   // 55  7
+			mem[  8] = {8'h36, 8'h49, 8'h49, 8'h49, 8'h36};   // 56  8
+			mem[  9] = {8'h06, 8'h49, 8'h49, 8'h29, 8'h1E};   // 57  9
+			mem[ 10] = {8'h7C, 8'h12, 8'h11, 8'h12, 8'h7C};   // 65  A
+			mem[ 11] = {8'h7F, 8'h49, 8'h49, 8'h49, 8'h36};   // 66  B
+			mem[ 12] = {8'h3E, 8'h41, 8'h41, 8'h41, 8'h22};   // 67  C
+			mem[ 13] = {8'h7F, 8'h41, 8'h41, 8'h22, 8'h1C};   // 68  D
+			mem[ 14] = {8'h7F, 8'h49, 8'h49, 8'h49, 8'h41};   // 69  E
+			mem[ 15] = {8'h7F, 8'h09, 8'h09, 8'h09, 8'h01};   // 70  F
+			mem[ 32] = {8'h00, 8'h00, 8'h00, 8'h00, 8'h00};   // 32  sp
+			mem[ 33] = {8'h00, 8'h00, 8'h2f, 8'h00, 8'h00};   // 33  !
+			mem[ 34] = {8'h00, 8'h07, 8'h00, 8'h07, 8'h00};   // 34
+			mem[ 35] = {8'h14, 8'h7f, 8'h14, 8'h7f, 8'h14};   // 35  #
+			mem[ 36] = {8'h24, 8'h2a, 8'h7f, 8'h2a, 8'h12};   // 36  $
+			mem[ 37] = {8'h62, 8'h64, 8'h08, 8'h13, 8'h23};   // 37  %
+			mem[ 38] = {8'h36, 8'h49, 8'h55, 8'h22, 8'h50};   // 38  &
+			mem[ 39] = {8'h00, 8'h05, 8'h03, 8'h00, 8'h00};   // 39  '
+			mem[ 40] = {8'h00, 8'h1c, 8'h22, 8'h41, 8'h00};   // 40  (
+			mem[ 41] = {8'h00, 8'h41, 8'h22, 8'h1c, 8'h00};   // 41  )
+			mem[ 42] = {8'h14, 8'h08, 8'h3E, 8'h08, 8'h14};   // 42  *
+			mem[ 43] = {8'h08, 8'h08, 8'h3E, 8'h08, 8'h08};   // 43  +
+			mem[ 44] = {8'h00, 8'h00, 8'hA0, 8'h60, 8'h00};   // 44  ,
+			mem[ 45] = {8'h08, 8'h08, 8'h08, 8'h08, 8'h08};   // 45  -
+			mem[ 46] = {8'h00, 8'h60, 8'h60, 8'h00, 8'h00};   // 46  .
+			mem[ 47] = {8'h20, 8'h10, 8'h08, 8'h04, 8'h02};   // 47  /
+			mem[ 48] = {8'h3E, 8'h51, 8'h49, 8'h45, 8'h3E};   // 48  0
+			mem[ 49] = {8'h00, 8'h42, 8'h7F, 8'h40, 8'h00};   // 49  1
+			mem[ 50] = {8'h42, 8'h61, 8'h51, 8'h49, 8'h46};   // 50  2
+			mem[ 51] = {8'h21, 8'h41, 8'h45, 8'h4B, 8'h31};   // 51  3
+			mem[ 52] = {8'h18, 8'h14, 8'h12, 8'h7F, 8'h10};   // 52  4
+			mem[ 53] = {8'h27, 8'h45, 8'h45, 8'h45, 8'h39};   // 53  5
+			mem[ 54] = {8'h3C, 8'h4A, 8'h49, 8'h49, 8'h30};   // 54  6
+			mem[ 55] = {8'h01, 8'h71, 8'h09, 8'h05, 8'h03};   // 55  7
+			mem[ 56] = {8'h36, 8'h49, 8'h49, 8'h49, 8'h36};   // 56  8
+			mem[ 57] = {8'h06, 8'h49, 8'h49, 8'h29, 8'h1E};   // 57  9
+			mem[ 58] = {8'h00, 8'h36, 8'h36, 8'h00, 8'h00};   // 58  :
+			mem[ 59] = {8'h00, 8'h56, 8'h36, 8'h00, 8'h00};   // 59  ;
+			mem[ 60] = {8'h08, 8'h14, 8'h22, 8'h41, 8'h00};   // 60  <
+			mem[ 61] = {8'h14, 8'h14, 8'h14, 8'h14, 8'h14};   // 61  =
+			mem[ 62] = {8'h00, 8'h41, 8'h22, 8'h14, 8'h08};   // 62  >
+			mem[ 63] = {8'h02, 8'h01, 8'h51, 8'h09, 8'h06};   // 63  ?
+			mem[ 64] = {8'h32, 8'h49, 8'h59, 8'h51, 8'h3E};   // 64  @
+			mem[ 65] = {8'h7C, 8'h12, 8'h11, 8'h12, 8'h7C};   // 65  A
+			mem[ 66] = {8'h7F, 8'h49, 8'h49, 8'h49, 8'h36};   // 66  B
+			mem[ 67] = {8'h3E, 8'h41, 8'h41, 8'h41, 8'h22};   // 67  C
+			mem[ 68] = {8'h7F, 8'h41, 8'h41, 8'h22, 8'h1C};   // 68  D
+			mem[ 69] = {8'h7F, 8'h49, 8'h49, 8'h49, 8'h41};   // 69  E
+			mem[ 70] = {8'h7F, 8'h09, 8'h09, 8'h09, 8'h01};   // 70  F
+			mem[ 71] = {8'h3E, 8'h41, 8'h49, 8'h49, 8'h7A};   // 71  G
+			mem[ 72] = {8'h7F, 8'h08, 8'h08, 8'h08, 8'h7F};   // 72  H
+			mem[ 73] = {8'h00, 8'h41, 8'h7F, 8'h41, 8'h00};   // 73  I
+			mem[ 74] = {8'h20, 8'h40, 8'h41, 8'h3F, 8'h01};   // 74  J
+			mem[ 75] = {8'h7F, 8'h08, 8'h14, 8'h22, 8'h41};   // 75  K
+			mem[ 76] = {8'h7F, 8'h40, 8'h40, 8'h40, 8'h40};   // 76  L
+			mem[ 77] = {8'h7F, 8'h02, 8'h0C, 8'h02, 8'h7F};   // 77  M
+			mem[ 78] = {8'h7F, 8'h04, 8'h08, 8'h10, 8'h7F};   // 78  N
+			mem[ 79] = {8'h3E, 8'h41, 8'h41, 8'h41, 8'h3E};   // 79  O
+			mem[ 80] = {8'h7F, 8'h09, 8'h09, 8'h09, 8'h06};   // 80  P
+			mem[ 81] = {8'h3E, 8'h41, 8'h51, 8'h21, 8'h5E};   // 81  Q
+			mem[ 82] = {8'h7F, 8'h09, 8'h19, 8'h29, 8'h46};   // 82  R
+			mem[ 83] = {8'h46, 8'h49, 8'h49, 8'h49, 8'h31};   // 83  S
+			mem[ 84] = {8'h01, 8'h01, 8'h7F, 8'h01, 8'h01};   // 84  T
+			mem[ 85] = {8'h3F, 8'h40, 8'h40, 8'h40, 8'h3F};   // 85  U
+			mem[ 86] = {8'h1F, 8'h20, 8'h40, 8'h20, 8'h1F};   // 86  V
+			mem[ 87] = {8'h3F, 8'h40, 8'h38, 8'h40, 8'h3F};   // 87  W
+			mem[ 88] = {8'h63, 8'h14, 8'h08, 8'h14, 8'h63};   // 88  X
+			mem[ 89] = {8'h07, 8'h08, 8'h70, 8'h08, 8'h07};   // 89  Y
+			mem[ 90] = {8'h61, 8'h51, 8'h49, 8'h45, 8'h43};   // 90  Z
+			mem[ 91] = {8'h00, 8'h7F, 8'h41, 8'h41, 8'h00};   // 91  [
+			mem[ 92] = {8'h55, 8'h2A, 8'h55, 8'h2A, 8'h55};   // 92  .
+			mem[ 93] = {8'h00, 8'h41, 8'h41, 8'h7F, 8'h00};   // 93  ]
+			mem[ 94] = {8'h04, 8'h02, 8'h01, 8'h02, 8'h04};   // 94  ^
+			mem[ 95] = {8'h40, 8'h40, 8'h40, 8'h40, 8'h40};   // 95  _
+			mem[ 96] = {8'h00, 8'h01, 8'h02, 8'h04, 8'h00};   // 96  '
+			mem[ 97] = {8'h20, 8'h54, 8'h54, 8'h54, 8'h78};   // 97  a
+			mem[ 98] = {8'h7F, 8'h48, 8'h44, 8'h44, 8'h38};   // 98  b
+			mem[ 99] = {8'h38, 8'h44, 8'h44, 8'h44, 8'h20};   // 99  c
+			mem[100] = {8'h38, 8'h44, 8'h44, 8'h48, 8'h7F};   // 100 d
+			mem[101] = {8'h38, 8'h54, 8'h54, 8'h54, 8'h18};   // 101 e
+			mem[102] = {8'h08, 8'h7E, 8'h09, 8'h01, 8'h02};   // 102 f
+			mem[103] = {8'h18, 8'hA4, 8'hA4, 8'hA4, 8'h7C};   // 103 g
+			mem[104] = {8'h7F, 8'h08, 8'h04, 8'h04, 8'h78};   // 104 h
+			mem[105] = {8'h00, 8'h44, 8'h7D, 8'h40, 8'h00};   // 105 i
+			mem[106] = {8'h40, 8'h80, 8'h84, 8'h7D, 8'h00};   // 106 j
+			mem[107] = {8'h7F, 8'h10, 8'h28, 8'h44, 8'h00};   // 107 k
+			mem[108] = {8'h00, 8'h41, 8'h7F, 8'h40, 8'h00};   // 108 l
+			mem[109] = {8'h7C, 8'h04, 8'h18, 8'h04, 8'h78};   // 109 m
+			mem[110] = {8'h7C, 8'h08, 8'h04, 8'h04, 8'h78};   // 110 n
+			mem[111] = {8'h38, 8'h44, 8'h44, 8'h44, 8'h38};   // 111 o
+			mem[112] = {8'hFC, 8'h24, 8'h24, 8'h24, 8'h18};   // 112 p
+			mem[113] = {8'h18, 8'h24, 8'h24, 8'h18, 8'hFC};   // 113 q
+			mem[114] = {8'h7C, 8'h08, 8'h04, 8'h04, 8'h08};   // 114 r
+			mem[115] = {8'h48, 8'h54, 8'h54, 8'h54, 8'h20};   // 115 s
+			mem[116] = {8'h04, 8'h3F, 8'h44, 8'h40, 8'h20};   // 116 t
+			mem[117] = {8'h3C, 8'h40, 8'h40, 8'h20, 8'h7C};   // 117 u
+			mem[118] = {8'h1C, 8'h20, 8'h40, 8'h20, 8'h1C};   // 118 v
+			mem[119] = {8'h3C, 8'h40, 8'h30, 8'h40, 8'h3C};   // 119 w
+			mem[120] = {8'h44, 8'h28, 8'h10, 8'h28, 8'h44};   // 120 x
+			mem[121] = {8'h1C, 8'hA0, 8'hA0, 8'hA0, 8'h7C};   // 121 y
+			mem[122] = {8'h44, 8'h64, 8'h54, 8'h4C, 8'h44};   // 122 z
+		end
+endmodule
+</code>
+### 通过DDS+PWM产生任意波形
+参见：[[pwm_awg|通过PWM生成任意波形模拟信号]]
+### 通过PWM产生可调电压
+参见：[[pwm_dc|通过PWM生成可调直流电压]]
+### 通过PWM和高速比较器实现低速串行ADC的功能
 {{ :fpga_adc.jpg |}}<WRAP centeralign> Sigma Delta实现ADC的模拟电路原理图 </WRAP>
-#### 通过高速比较器实现频率计的功能
-#### 板上电压的产生
+### 通过高速比较器实现频率计的功能
+参见[[digital_frequency_meter|全国大学生电子设计竞赛中的数字频率计的实现]]
+### 板上电压的产生
 如前面所述，模拟电路部分需要如下几组电压：
   * +3.3V/-3.3V，为运算放大器提供双轨的供电电压
   * +3.0V/+1.5V，为AWG的输出和DC的调节提供运算放大器的直流偏移
-### 参考资料