【国产FPGA高云GW1N-4系列开发板测评】——11、点个LCD1602屏

gs001588 发表于 2022-1-20 20:55

本帖最后由 gs001588 于 2022-1-20 20:55 编辑

   【国产FPGA高云GW1N-4系列开发板测评】——11、点个LCD1602屏

   

   之前用在FPGA上写过12864带字库屏的显示应用，间隔时间比较长了，之前备份的资料暂时没有找到。手头正好有LCD1602的LCD屏，不妨先拿LCD1602来做个显示实验。LCD1602作为一款经典的LCD屏，在各种学习平台上的应用自然是少不了的，在FPGA上也不例外。

   本着拿来主义的想法，参考网友资料，做了适当修改。原本打算做成显存方式模块，对外接口为异步RAM方式，模块内部完成LCD初始化，有新显存数据后自动显示刷新操作。这样就需要写顶层文件，需要提供变化的数据源，把问题复杂化，因此可作为之后的改进实验。本贴先显示一下LCD1602。

   参考网址（<a href="https://blog.csdn.net/qq_33231534/article/details/108484995" target="_blank">基于FPGA的LCD1602显示屏驱动 https://blog.csdn.net/qq_33231534/article/details/108484995</a>）

 

   本实验使用到的FPGA管脚资源配置如下： 


 

  GWIN-4B与LCD1602屏之间对应关系接线表：

<table align="center" border="1" cellpadding="1" cellspacing="1">
<tbody>
<tr>
<td>LCD1602</td>
<td>功能说明</td>
<td>GWIN-4B</td>
</tr>
<tr>
<td>1、VCC</td>
<td>电源地</td>
<td>JP7.2-5V</td>
</tr>
<tr>
<td>2、GND</td>
<td>电源正极</td>
<td>J19.1-GND</td>
</tr>
<tr>
<td rowspan="1">
3、V0（接5.1K到GND）
</td>
<td rowspan="1">液晶显示偏压</td>
<td rowspan="1"> </td>
</tr>
<tr>
<td>4、RS</td>
<td>命令/数据选择</td>
<td>J4.1-32</td>
</tr>
<tr>
<td>5、RW</td>
<td>读/写选择</td>
<td>J4.2-34</td>
</tr>
<tr>
<td>6、EN</td>
<td>使能信号</td>
<td>J4.3-38</td>
</tr>
<tr>
<td>7、DATA0</td>
<td>数据0</td>
<td>J4.4-39</td>
</tr>
<tr>
<td>
8、DATA1
</td>
<td>数据1</td>
<td>J4.5-40</td>
</tr>
<tr>
<td>9、DATA2</td>
<td>数据2</td>
<td>J4.6-41</td>
</tr>
<tr>
<td>10、DATA3</td>
<td>数据3</td>
<td>J4.7-42</td>
</tr>
<tr>
<td>11、DATA4</td>
<td>数据4</td>
<td>J4.8-43</td>
</tr>
<tr>
<td>12、DATA5</td>
<td>数据5</td>
<td>J4.9-44</td>
</tr>
<tr>
<td>
13、DATA6
</td>
<td>数据6</td>
<td>J4.10-45</td>
</tr>
<tr>
<td>14、DATA7</td>
<td>数据7</td>
<td>J4.11-46</td>
</tr>
<tr>
<td>15、A（5V）</td>
<td>背光正极</td>
<td>JP7.1-5V</td>
</tr>
<tr>
<td>16、K（GND）</td>
<td>背光负极</td>
<td>J19.16-GND</td>
</tr>
</tbody>
</table>

 

   LCD1602的1、3脚之间并个5.1K直插电阻，为3脚的液晶显示偏置电压V0提供参考。一般开发板上使用的话会在1、3脚之间接个10K的电位器来调节电压，为啥是5.1K？之前修过一块开发板，在板上3脚接到GND了，导致普通LCD1602不能显示。查询LCD1602数据手册，此管脚V0为液晶显示偏压，接地时对比度最高，对比度过高时会产生“鬼影”，显示发黑不易区分正常显示与底色；接正电源电压时对比度最弱，显示发白几乎看不见。接个5K左右的电阻即可正常显示，电阻不需要精确4到6K都可以。



 

   正好JP7有两针5V引出，其中一个给LCD逻辑供电，另一个给背光正极供电；GND比较多，随意选了两个，一个作为电源地，另一个作为背光负极。



 

   剩余11条数据线分别一一对应接到JP14的1到11脚。



 

   逻辑代码见下。具体功能及LCD1602相关寄存器功能等可以参考上面的“参考网址”中相关内容。

<pre>
<code>module lcd(
input clk ,
input rst_n ,

output reg lcd_rs ,
output wire lcd_rw ,
output reg lcd_en ,
output reg lcd_data
);

reg cnt ;
reg state_c ;
reg state_n ;
reg char_cnt ;
reg data_display ;

localparam
IDLE = 4'd0 ,
INIT = 4'd1 ,
S0 = 4'd2 ,
S1 = 4'd3 ,
S2 = 4'd4 ,
S3 = 4'd5 ,
ROW1_ADDR = 4'd6 ,
WRITE = 4'd7 ,
ROW2_ADDR = 4'd8 ,
stop = 4'd9 ;

reg disp_memory ;
reg disp_cnt;

assign lcd_rw = 1'b0;

always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
cnt <= 17'd0;
end
else begin
if (cnt==17'd100_000 - 1) begin
cnt <= 17'd0;
end
else begin
cnt <= cnt + 1'b1;
end
end
end

always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
lcd_en <= 0;
end
else if (cnt==17'd50_000 - 1) begin
lcd_en <= 1;
end
else if (cnt==17'd100_000 - 1) begin
lcd_en <= 0;
end
end

always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
char_cnt <= 0;
end
else if (state_c==WRITE && cnt==17'd50_000 - 1) begin
if (char_cnt==5'd31) begin
char_cnt <= 5'd0;
end
else begin
char_cnt <= char_cnt + 1'b1;
end
end
end

integer i;

always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
 for(i=0;i<32;i=i+1)
 begin
 case(i)
 5'd0: data_display = "W";
 5'd1: data_display = "e";
 5'd2: data_display = "l";
 5'd3: data_display = "c";
 5'd4: data_display = "o";
 5'd5: data_display = "m";
 5'd6: data_display = "e";
 5'd7: data_display = " ";
 5'd8: data_display = "t";
 5'd9: data_display = "o";
 5'd10: data_display= " ";
 5'd11: data_display= "G";
 5'd12: data_display= "O";
 5'd13: data_display= "W";
 5'd14: data_display= "I";
 5'd15: data_display= "N";

 5'd16: data_display= "M";
 5'd17: data_display= "i";
 5'd18: data_display= "n";
 5'd19: data_display= "i";
 5'd20: data_display= " ";
 5'd21: data_display= "K";
 5'd22: data_display= "i";
 5'd23: data_display= "T";
 5'd24: data_display= " ";
 5'd25: data_display= "G";
 5'd26: data_display= "W";
 5'd27: data_display= "I";
 5'd28: data_display= "N";
 5'd29: data_display= "-";
 5'd30: data_display= "4";
 5'd31: data_display= "B";

 default:data_display = "P";
 endcase

 disp_memory = data_display;
 end
end
end

always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
state_c <= IDLE;
end
else if(cnt==17'd50_000 - 1) begin
state_c <= state_n;
end
end

reg cnt_15ms;
reg flag ;
always@(posedge clk or negedge rst_n)begin
if (!rst_n) begin
cnt_15ms <= 0;
end
else if (state_c == IDLE) begin
cnt_15ms <= cnt_15ms + 1'b1;
end
end

always@(posedge clk or negedge rst_n)begin
if (!rst_n) begin
flag <= 0;
end
else if (state_c==IDLE && cnt_15ms==20'd750000) begin
flag <= 1;
end
end

always @(*) begin
case(state_c)
IDLE :
begin
if (flag) begin
state_n = INIT;
end
else begin
state_n = state_c;
end
end
INIT :
begin
state_n = S0;
end
S0 :
begin
state_n = S1;
end
S1 :
begin
state_n = S2;
end
S2 :
begin
state_n = S3;
end
S3 :
begin
state_n = ROW1_ADDR;
end
ROW1_ADDR:
begin
state_n = WRITE;
end
WRITE :
begin
if (char_cnt==5'd15) begin
state_n = ROW2_ADDR;
end
else if (char_cnt==5'd31) begin
state_n = stop;
end
else begin
state_n = state_c;
end
end
ROW2_ADDR:
begin
state_n = WRITE;
end
stop :
begin
state_n = stop;
end
default:state_n = IDLE;
endcase
end

always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
lcd_data <= 8'd0;
end
else begin
case(state_c)
IDLE :begin lcd_data <= 8'h38; lcd_rs <= 0;end
INIT :begin lcd_data <= 8'h38; lcd_rs <= 0;end
S0 :begin lcd_data <= 8'h08; lcd_rs <= 0;end
S1 :begin lcd_data <= 8'h01; lcd_rs <= 0;end
S2 :begin lcd_data <= 8'h06; lcd_rs <= 0;end
S3 :begin lcd_data <= 8'h0c; lcd_rs <= 0;end
ROW1_ADDR :begin lcd_data <= 8'h80; lcd_rs <= 0;end
//WRITE :begin lcd_data <= data_display; lcd_rs <= 1;end
 WRITE :begin lcd_data <= disp_memory; lcd_rs <= 1;end
ROW2_ADDR :begin lcd_data <= 8'hc0; lcd_rs <= 0;end
stop :begin lcd_data <= 8'h38; lcd_rs <= 0;end
default:;
endcase
end
end
endmodule
</code></pre>

 

   本实验用到了复位功能，将双功能管脚选项中的RECONFIG_N作为普通IO选项打勾。



 

   逻辑代码编译通过，下载到开发板，LCD1602两行分别显示“Welcome to GOWIN”、“Mini KiT GWIN-4B”，效果见下图。



 

   本实验完成将LCD1602屏点亮显示字符。

   疫情原因无法正常上般，家里条件有限，手头缺少扩展模块来实验，更多扩展功能之后有时间补上。

nmg 发表于 2022-1-21 10:08

熟悉的lcd1602，我以为它已经被淘汰了

希望是疫情最后一波，明年可以解放啦

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【国产FPGA高云GW1N-4系列开发板测评】——11、点个LCD1602屏