前面说过，在C,C++等语言学习中，“Hello World”将会是第一个学习的代码，但是在FPGA中由于电路驱动的复杂性，与单片机雷同，我们无法在电脑上实现“Hello World”的显示，而必须依靠相关硬件。因此我们不得不在一定的基础上，才能讲解关于LCD1602字符液晶的驱动，以及Hello World的显示。

雷同于前面MCU按键消抖动移植代码，此处也可以移植MCU LCD1602驱动代码。本例程不是Bingo原创，是按照网友“小时不识月”的代码，移植修改最后定型为Bingo版本(O(∩_∩)O哈哈~)。

电路图此处不解释，太简单了。

(资料图)

一、驱动说明

由于FPGA的高速并行操作，并非顺序执行，在代码上与MCU有所不同。此处先讲解驱动原理：

(1)分频以得到500KHz固定的频率，初始化LCD1602。如下图所示，LCD_EN的频率应该控制在2M以内(不同的LCD1602参数会有所不同)。

(2)通过三段式状态机，来初始化以及给数据。

(3)通过循环读取某一“数组”，循环给LCD1602数据，以接口形式方便改变。

二、FPGA LCD1602 FSM

1. 代码

/*************************************************

* Module Name : lcd1602_driver

* Engineer : Crazy Bingo

* Target Device : EP2C8Q208C8

* Tool versions : Quartus II 11.0

* Create Date : 2011-7-3

* Revision : v1.0

* Description :

**************************************************/

module lcd1602_driver

(

input clk,

input rst_n,

output lcd_en, // lcd enable

output reg lcd_rs, // record,statement

output lcd_rw,

output reg [7:0] lcd_data

);

parameter [127:0] line_rom1 = "I am CrazyBingo!";

parameter [127:0] line_rom2 = "Hello World*^_^*";

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

reg [15:0] cnt;

always @ (posedge clk or negedge rst_n)

begin

if(!rst_n)

cnt <= 0;

else

cnt <= cnt + 1"b1;

end

assign lcd_en = cnt[15]; //lcd enable,keep same time

assign lcd_rw = 1"b0; //write only

wire cmd_flag = (cnt == 16"h7FFF) ? 1"b1 : 1"b0; //when lcd_en is steady,write a cmd

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

// Gray code : 40 states

parameter IDLE = 8"h00; // IDLE

// lcd init

parameter DISP_SET = 8"h01; // display mode

parameter DISP_OFF = 8"h03; // off display

parameter CLR_SCR = 8"h02; // clear the lcd

parameter CURSOR_SET1 = 8"h06; // cursor set

parameter CURSOR_SET2 = 8"h07; // on display, cursor set

// display 1th line

parameter ROW1_ADDR = 8"h05;

parameter ROW1_0 = 8"h04;

parameter ROW1_1 = 8"h0C;

parameter ROW1_2 = 8"h0D;

parameter ROW1_3 = 8"h0F;

parameter ROW1_4 = 8"h0E;

parameter ROW1_5 = 8"h0A;

parameter ROW1_6 = 8"h0B;

parameter ROW1_7 = 8"h09;

parameter ROW1_8 = 8"h08;

parameter ROW1_9 = 8"h18;

parameter ROW1_A = 8"h19;

parameter ROW1_B = 8"h1B;

parameter ROW1_C = 8"h1A;

parameter ROW1_D = 8"h1E;

parameter ROW1_E = 8"h1F;

parameter ROW1_F = 8"h1D;

// display 2th line

parameter ROW2_ADDR = 8"h1C;

parameter ROW2_0 = 8"h14;

parameter ROW2_1 = 8"h15;

parameter ROW2_2 = 8"h17;

parameter ROW2_3 = 8"h16;

parameter ROW2_4 = 8"h12;

parameter ROW2_5 = 8"h13;

parameter ROW2_6 = 8"h11;

parameter ROW2_7 = 8"h10;

parameter ROW2_8 = 8"h30;

parameter ROW2_9 = 8"h31;

parameter ROW2_A = 8"h33;

parameter ROW2_B = 8"h32;

parameter ROW2_C = 8"h36;

parameter ROW2_D = 8"h37;

parameter ROW2_E = 8"h35;

parameter ROW2_F = 8"h34;

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

reg [5:0] current_state, next_state;

// FSM: always1

always @ (posedge clk or negedge rst_n)

begin

if(!rst_n)

current_state <= IDLE;

else if(cmd_flag)

current_state <= next_state;

end

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

// FSM: always2

always@*

begin

case(current_state)

// lcd init

IDLE : next_state = DISP_SET;

DISP_SET : next_state = DISP_OFF;

DISP_OFF : next_state = CLR_SCR;

CLR_SCR : next_state = CURSOR_SET1;

CURSOR_SET1 : next_state = CURSOR_SET2;

CURSOR_SET2 : next_state = ROW1_ADDR;

// display 1th line

ROW1_ADDR : next_state = ROW1_0;

ROW1_0 : next_state = ROW1_1;

ROW1_1 : next_state = ROW1_2;

ROW1_2 : next_state = ROW1_3;

ROW1_3 : next_state = ROW1_4;

ROW1_4 : next_state = ROW1_5;

ROW1_5 : next_state = ROW1_6;

ROW1_6 : next_state = ROW1_7;

ROW1_7 : next_state = ROW1_8;

ROW1_8 : next_state = ROW1_9;

ROW1_9 : next_state = ROW1_A;

ROW1_A : next_state = ROW1_B;

ROW1_B : next_state = ROW1_C;

ROW1_C : next_state = ROW1_D;

ROW1_D : next_state = ROW1_E;

ROW1_E : next_state = ROW1_F;

ROW1_F : next_state = ROW2_ADDR;

// display 2th line

ROW2_ADDR : next_state = ROW2_0;

ROW2_0 : next_state = ROW2_1;

ROW2_1 : next_state = ROW2_2;

ROW2_2 : next_state = ROW2_3;

ROW2_3 : next_state = ROW2_4;

ROW2_4 : next_state = ROW2_5;

ROW2_5 : next_state = ROW2_6;

ROW2_6 : next_state = ROW2_7;

ROW2_7 : next_state = ROW2_8;

ROW2_8 : next_state = ROW2_9;

ROW2_9 : next_state = ROW2_A;

ROW2_A : next_state = ROW2_B;

ROW2_B : next_state = ROW2_C;

ROW2_C : next_state = ROW2_D;

ROW2_D : next_state = ROW2_E;

ROW2_E : next_state = ROW2_F;

ROW2_F : next_state = ROW1_ADDR;

default : next_state = IDLE ;

endcase

end

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

// FSM: always3

always @ (posedge clk or negedge rst_n)

begin

if(!rst_n)

begin

lcd_rs <= 0;

lcd_data <= 8"hXX;

end

else if(cmd_flag)

begin

// write statement

case(next_state)

IDLE : lcd_rs <= 0; //statement

//lcd init

DISP_SET : lcd_rs <= 0; //statement

DISP_OFF : lcd_rs <= 0; //statement

CLR_SCR : lcd_rs <= 0; //statement

CURSOR_SET1 : lcd_rs <= 0; //statement

CURSOR_SET2 : lcd_rs <= 0; //statement

// display 1th line

ROW1_ADDR : lcd_rs <= 0; //statement

ROW1_0 : lcd_rs <= 1; //record

ROW1_1 : lcd_rs <= 1; //record

ROW1_2 : lcd_rs <= 1; //record

ROW1_3 : lcd_rs <= 1; //record

ROW1_4 : lcd_rs <= 1; //record

ROW1_5 : lcd_rs <= 1; //record

ROW1_6 : lcd_rs <= 1; //record

ROW1_7 : lcd_rs <= 1; //record

ROW1_8 : lcd_rs <= 1; //record

ROW1_9 : lcd_rs <= 1; //record

ROW1_A : lcd_rs <= 1; //record

ROW1_B : lcd_rs <= 1; //record

ROW1_C : lcd_rs <= 1; //record

ROW1_D : lcd_rs <= 1; //record

ROW1_E : lcd_rs <= 1; //record

ROW1_F : lcd_rs <= 1; //record

// display 2th line

ROW2_ADDR : lcd_rs <= 0; //statement

ROW2_0 : lcd_rs <= 1; //record

ROW2_1 : lcd_rs <= 1; //record

ROW2_2 : lcd_rs <= 1; //record

ROW2_3 : lcd_rs <= 1; //record

ROW2_4 : lcd_rs <= 1; //record

ROW2_5 : lcd_rs <= 1; //record

ROW2_6 : lcd_rs <= 1; //record

ROW2_7 : lcd_rs <= 1; //record

ROW2_8 : lcd_rs <= 1; //record

ROW2_9 : lcd_rs <= 1; //record

ROW2_A : lcd_rs <= 1; //record

ROW2_B : lcd_rs <= 1; //record

ROW2_C : lcd_rs <= 1; //record

ROW2_D : lcd_rs <= 1; //record

ROW2_E : lcd_rs <= 1; //record

ROW2_F : lcd_rs <= 1; //record

endcase

// write lcd_data

case(next_state)

IDLE : lcd_data <= 8"hxx;

//lcd init

DISP_SET : lcd_data <= 8"h38; //set 16X2,5X7 ,8 bits record

DISP_OFF : lcd_data <= 8"h08; //off display

CLR_SCR : lcd_data <= 8"h01; //clear lcd

CURSOR_SET1 : lcd_data <= 8"h06; //cursor set

CURSOR_SET2 : lcd_data <= 8"h0C; //on display

// display 1th line

ROW1_ADDR : lcd_data <= 8"h80;

ROW1_0 : lcd_data <= line_rom1[127:120];

ROW1_1 : lcd_data <= line_rom1[119:112];

ROW1_2 : lcd_data <= line_rom1[111:104];

ROW1_3 : lcd_data <= line_rom1[103: 96];

ROW1_4 : lcd_data <= line_rom1[ 95: 88];

ROW1_5 : lcd_data <= line_rom1[ 87: 80];

ROW1_6 : lcd_data <= line_rom1[ 79: 72];

ROW1_7 : lcd_data <= line_rom1[ 71: 64];

ROW1_8 : lcd_data <= line_rom1[ 63: 56];

ROW1_9 : lcd_data <= line_rom1[ 55: 48];

ROW1_A : lcd_data <= line_rom1[ 47: 40];

ROW1_B : lcd_data <= line_rom1[ 39: 32];

ROW1_C : lcd_data <= line_rom1[ 31: 24];

ROW1_D : lcd_data <= line_rom1[ 23: 16];

ROW1_E : lcd_data <= line_rom1[ 15: 8];

ROW1_F : lcd_data <= line_rom1[ 7: 0];

// display 2th line

ROW2_ADDR : lcd_data <= 8"hC0;

ROW2_0 : lcd_data <= line_rom2[127:120];

ROW2_1 : lcd_data <= line_rom2[119:112];

ROW2_2 : lcd_data <= line_rom2[111:104];

ROW2_3 : lcd_data <= line_rom2[103: 96];

ROW2_4 : lcd_data <= line_rom2[ 95: 88];

ROW2_5 : lcd_data <= line_rom2[ 87: 80];

ROW2_6 : lcd_data <= line_rom2[ 79: 72];

ROW2_7 : lcd_data <= line_rom2[ 71: 64];

ROW2_8 : lcd_data <= line_rom2[ 63: 56];

ROW2_9 : lcd_data <= line_rom2[ 55: 48];

ROW2_A : lcd_data <= line_rom2[ 47: 40];

ROW2_B : lcd_data <= line_rom2[ 39: 32];

ROW2_C : lcd_data <= line_rom2[ 31: 24];

ROW2_D : lcd_data <= line_rom2[ 23: 16];

ROW2_E : lcd_data <= line_rom2[ 15: 8];

ROW2_F : lcd_data <= line_rom2[ 7: 0];

endcase

end

end

endmodule

2. 状态机

(1)以下是State machine如下所示：

(2)模块可分为一下几个状态

3. “Hello World”实物显示

parameter [127:0] line_rom1 = "I am CrazyBingo!";

parameter [127:0] line_rom2 = "Hello World*^_^*";