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http://www.johnloomis.org/digitallab/lcdlab/lcdlab3/lcdlab3.qdoc.html
Verilog Files
lcdlab3.v
module lcdlab3(
input CLOCK_50, // 50 MHz clock
input [3:0] KEY, // Pushbutton[3:0]
input [17:0] SW, // Toggle Switch[17:0]
output [6:0] HEX0,HEX1,HEX2,HEX3,HEX4,HEX5,HEX6,HEX7, // Seven Segment Digits
output [8:0] LEDG, // LED Green
output [17:0] LEDR, // LED Red
inout [35:0] GPIO_0,GPIO_1, // GPIO Connections
// LCD Module 16X2
output LCD_ON, // LCD Power ON/OFF
output LCD_BLON, // LCD Back Light ON/OFF
output LCD_RW, // LCD Read/Write Select, 0 = Write, 1 = Read
output LCD_EN, // LCD Enable
output LCD_RS, // LCD Command/Data Select, 0 = Command, 1 = Data
inout [7:0] LCD_DATA // LCD Data bus 8 bits
);
// All inout port turn to tri-state
assign GPIO_0 = 36'hzzzzzzzzz;
assign GPIO_1 = 36'hzzzzzzzzz;
wire [6:0] myclock;
wire RST;
assign RST = KEY[0];
// reset delay gives some time for peripherals to initialize
wire DLY_RST;
Reset_Delay r0( .iCLK(CLOCK_50),.oRESET(DLY_RST) );
// Send switches to red leds
assign LEDR = SW;
// turn LCD ON
assign LCD_ON = 1'b1;
assign LCD_BLON = 1'b1;
wire [3:0] hex1, hex0;
assign hex1 = SW[7:4];
assign hex0 = SW[3:0];
LCD_Display u1(
// Host Side
.iCLK_50MHZ(CLOCK_50),
.iRST_N(DLY_RST),
.hex0(hex0),
.hex1(hex1),
// LCD Side
.DATA_BUS(LCD_DATA),
.LCD_RW(LCD_RW),
.LCD_E(LCD_EN),
.LCD_RS(LCD_RS)
);
// blank unused 7-segment digits
assign HEX0 = 7'b111_1111;
assign HEX1 = 7'b111_1111;
assign HEX2 = 7'b111_1111;
assign HEX3 = 7'b111_1111;
assign HEX4 = 7'b111_1111;
assign HEX5 = 7'b111_1111;
assign HEX6 = 7'b111_1111;
assign HEX7 = 7'b111_1111;
endmodule
LCD_Display.v
/*
SW8 (GLOBAL RESET) resets LCD
ENTITY LCD_Display IS
-- Enter number of live Hex hardware data values to display
-- (do not count ASCII character constants)
GENERIC(Num_Hex_Digits: Integer:= 2);
-----------------------------------------------------------------------
-- LCD Displays 16 Characters on 2 lines
-- LCD_display string is an ASCII character string entered in hex for
-- the two lines of the LCD Display (See ASCII to hex table below)
-- Edit LCD_Display_String entries above to modify display
-- Enter the ASCII character's 2 hex digit equivalent value
-- (see table below for ASCII hex values)
-- To display character assign ASCII value to LCD_display_string(x)
-- To skip a character use 8'h20" (ASCII space)
-- To dislay "live" hex values from hardware on LCD use the following:
-- make array element for that character location 8'h0" & 4-bit field from Hex_Display_Data
-- state machine sees 8'h0" in high 4-bits & grabs the next lower 4-bits from Hex_Display_Data input
-- and performs 4-bit binary to ASCII conversion needed to print a hex digit
-- Num_Hex_Digits must be set to the count of hex data characters (ie. "00"s) in the display
-- Connect hardware bits to display to Hex_Display_Data input
-- To display less than 32 characters, terminate string with an entry of 8'hFE"
-- (fewer characters may slightly increase the LCD's data update rate)
-------------------------------------------------------------------
-- ASCII HEX TABLE
-- Hex Low Hex Digit
-- Value 0 1 2 3 4 5 6 7 8 9 A B C D E F
------\----------------------------------------------------------------
--H 2 | SP ! " # $ % & ' ( ) * + , - . /
--i 3 | 0 1 2 3 4 5 6 7 8 9 : ; < = > ?
--g 4 | @ A B C D E F G H I J K L M N O
--h 5 | P Q R S T U V W X Y Z [ \ ] ^ _
-- 6 | ` a b c d e f g h i j k l m n o
-- 7 | p q r s t u v w x y z { | } ~ DEL
-----------------------------------------------------------------------
-- Example "A" is row 4 column 1, so hex value is 8'h41"
-- *see LCD Controller's Datasheet for other graphics characters available
*/
module LCD_Display(iCLK_50MHZ, iRST_N, hex1, hex0,
LCD_RS,LCD_E,LCD_RW,DATA_BUS);
input iCLK_50MHZ, iRST_N;
input [3:0] hex1, hex0;
output LCD_RS, LCD_E, LCD_RW;
inout [7:0] DATA_BUS;
parameter
HOLD = 4'h0,
FUNC_SET = 4'h1,
DISPLAY_ON = 4'h2,
MODE_SET = 4'h3,
Print_String = 4'h4,
LINE2 = 4'h5,
RETURN_HOME = 4'h6,
DROP_LCD_E = 4'h7,
RESET1 = 4'h8,
RESET2 = 4'h9,
RESET3 = 4'ha,
DISPLAY_OFF = 4'hb,
DISPLAY_CLEAR = 4'hc;
reg [3:0] state, next_command;
// Enter new ASCII hex data above for LCD Display
reg [7:0] DATA_BUS_VALUE;
wire [7:0] Next_Char;
reg [19:0] CLK_COUNT_400HZ;
reg [4:0] CHAR_COUNT;
reg CLK_400HZ, LCD_RW_INT, LCD_E, LCD_RS;
// BIDIRECTIONAL TRI STATE LCD DATA BUS
assign DATA_BUS = (LCD_RW_INT? 8'bZZZZZZZZ: DATA_BUS_VALUE);
LCD_display_string u1(
.index(CHAR_COUNT),
.out(Next_Char),
.hex1(hex1),
.hex0(hex0));
assign LCD_RW = LCD_RW_INT;
always @(posedge iCLK_50MHZ or negedge iRST_N)
if (!iRST_N)
begin
CLK_COUNT_400HZ <= 20'h00000;
CLK_400HZ <= 1'b0;
end
else if (CLK_COUNT_400HZ < 20'h0F424)
begin
CLK_COUNT_400HZ <= CLK_COUNT_400HZ + 1'b1;
end
else
begin
CLK_COUNT_400HZ <= 20'h00000;
CLK_400HZ <= ~CLK_400HZ;
end
// State Machine to send commands and data to LCD DISPLAY
always @(posedge CLK_400HZ or negedge iRST_N)
if (!iRST_N)
begin
state <= RESET1;
end
else
case (state)
RESET1:
// Set Function to 8-bit transfer and 2 line display with 5x8 Font size
// see Hitachi HD44780 family data sheet for LCD command and timing details
begin
LCD_E <= 1'b1;
LCD_RS <= 1'b0;
LCD_RW_INT <= 1'b0;
DATA_BUS_VALUE <= 8'h38;
state <= DROP_LCD_E;
next_command <= RESET2;
CHAR_COUNT <= 5'b00000;
end
RESET2:
begin
LCD_E <= 1'b1;
LCD_RS <= 1'b0;
LCD_RW_INT <= 1'b0;
DATA_BUS_VALUE <= 8'h38;
state <= DROP_LCD_E;
next_command <= RESET3;
end
RESET3:
begin
LCD_E <= 1'b1;
LCD_RS <= 1'b0;
LCD_RW_INT <= 1'b0;
DATA_BUS_VALUE <= 8'h38;
state <= DROP_LCD_E;
next_command <= FUNC_SET;
end
// EXTRA STATES ABOVE ARE NEEDED FOR RELIABLE PUSHBUTTON RESET OF LCD
FUNC_SET:
begin
LCD_E <= 1'b1;
LCD_RS <= 1'b0;
LCD_RW_INT <= 1'b0;
DATA_BUS_VALUE <= 8'h38;
state <= DROP_LCD_E;
next_command <= DISPLAY_OFF;
end
// Turn off Display and Turn off cursor
DISPLAY_OFF:
begin
LCD_E <= 1'b1;
LCD_RS <= 1'b0;
LCD_RW_INT <= 1'b0;
DATA_BUS_VALUE <= 8'h08;
state <= DROP_LCD_E;
next_command <= DISPLAY_CLEAR;
end
// Clear Display and Turn off cursor
DISPLAY_CLEAR:
begin
LCD_E <= 1'b1;
LCD_RS <= 1'b0;
LCD_RW_INT <= 1'b0;
DATA_BUS_VALUE <= 8'h01;
state <= DROP_LCD_E;
next_command <= DISPLAY_ON;
end
// Turn on Display and Turn off cursor
DISPLAY_ON:
begin
LCD_E <= 1'b1;
LCD_RS <= 1'b0;
LCD_RW_INT <= 1'b0;
DATA_BUS_VALUE <= 8'h0C;
state <= DROP_LCD_E;
next_command <= MODE_SET;
end
// Set write mode to auto increment address and move cursor to the right
MODE_SET:
begin
LCD_E <= 1'b1;
LCD_RS <= 1'b0;
LCD_RW_INT <= 1'b0;
DATA_BUS_VALUE <= 8'h06;
state <= DROP_LCD_E;
next_command <= Print_String;
end
// Write ASCII hex character in first LCD character location
Print_String:
begin
state <= DROP_LCD_E;
LCD_E <= 1'b1;
LCD_RS <= 1'b1;
LCD_RW_INT <= 1'b0;
// ASCII character to output
if (Next_Char[7:4] != 4'h0)
DATA_BUS_VALUE <= Next_Char;
// Convert 4-bit value to an ASCII hex digit
else if (Next_Char[3:0] >9)
// ASCII A...F
DATA_BUS_VALUE <= {4'h4,Next_Char[3:0]-4'h9};
else
// ASCII 0...9
DATA_BUS_VALUE <= {4'h3,Next_Char[3:0]};
// Loop to send out 32 characters to LCD Display (16 by 2 lines)
if ((CHAR_COUNT < 31) && (Next_Char != 8'hFE))
CHAR_COUNT <= CHAR_COUNT + 1'b1;
else
CHAR_COUNT <= 5'b00000;
// Jump to second line?
if (CHAR_COUNT == 15)
next_command <= LINE2;
// Return to first line?
else if ((CHAR_COUNT == 31) || (Next_Char == 8'hFE))
next_command <= RETURN_HOME;
else
next_command <= Print_String;
end
// Set write address to line 2 character 1
LINE2:
begin
LCD_E <= 1'b1;
LCD_RS <= 1'b0;
LCD_RW_INT <= 1'b0;
DATA_BUS_VALUE <= 8'hC0;
state <= DROP_LCD_E;
next_command <= Print_String;
end
// Return write address to first character postion on line 1
RETURN_HOME:
begin
LCD_E <= 1'b1;
LCD_RS <= 1'b0;
LCD_RW_INT <= 1'b0;
DATA_BUS_VALUE <= 8'h80;
state <= DROP_LCD_E;
next_command <= Print_String;
end
// The next three states occur at the end of each command or data transfer to the LCD
// Drop LCD E line - falling edge loads inst/data to LCD controller
DROP_LCD_E:
begin
LCD_E <= 1'b0;
state <= HOLD;
end
// Hold LCD inst/data valid after falling edge of E line
HOLD:
begin
state <= next_command;
end
endcase
endmodule
module LCD_display_string(index,out,hex0,hex1);
input [4:0] index;
input [3:0] hex0,hex1;
output [7:0] out;
reg [7:0] out;
// ASCII hex values for LCD Display
// Enter Live Hex Data Values from hardware here
// LCD DISPLAYS THE FOLLOWING:
//----------------------------
//| Count=XX |
//| DE2 |
//----------------------------
// Line 1
always
case (index)
5'h00: out <= 8'h43;
5'h01: out <= 8'h6F;
5'h02: out <= 8'h75;
5'h03: out <= 8'h6E;
5'h04: out <= 8'h74;
5'h05: out <= 8'h3D;
5'h06: out <= {4'h0,hex1};
5'h07: out <= {4'h0,hex0};
// Line 2
5'h10: out <= 8'h44;
5'h11: out <= 8'h45;
5'h12: out <= 8'h32;
default: out <= 8'h20;
endcase
endmodule
reset_delay.v
module Reset_Delay(iCLK,oRESET);
input iCLK;
output reg oRESET;
reg [19:0] Cont;
always@(posedge iCLK)
begin
if(Cont!=20'hFFFFF)
begin
Cont <= Cont+1'b1;
oRESET <= 1'b0;
end
else
oRESET <= 1'b1;
end
endmodule
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