LCD

Overview

LCD is designed for the Hackaday Badge 2019, 480 x 320. 16b / pixel. Arranged as 5’Red, 6’Green, 5’Blue. It has a frame buffer.

Mostly LCD will be used inside higher level modules to provide more than just fill and rectangle services.

Basic operations are Write Rectangle and Read Rectangle and Fill Rect.

Commands are issued on the command port.

Modules

There are several LCD Modules

• lcd
• lcd_proxy

LCD

LCD connects to the panel, sends the initialization command stream, then sits and waits for commands.

The module responds to a few commands (defined in lcd_defs.v)

• LCD_COMMAND_CONFIGURE - configures the panel - must be called before other commands will work
• LCD_COMMAND_FILL_RECT - puts a single color (fill_pixel) in the specified rectangle (rect_x0,rect_y0,rect_x1,rect_y1)
• LCD_COMMAND_WRITE_RECT - writes into the specified rectangle, pixels supplied to the rect_pixel_write port
• LCD_COMMAND_READ_RECT - reads pixels from a rectangle, pixels output to the rect_pixel_read_port

Many of the parameters of the design are brought out as module parameters, however the default values work with the present hardware, so they can be left untouched. Being able to change them helps with simulation (where sometimes, for example, smaller panels are created to shorten simulation time)

Parameters

Name	Description	Default	Comment
Width	Width of the panel	480
Height	Height of the panel	320
CoordinateWidth	Width of all co-ordinates	9
DataWidth	Width of the data path to the LCD	18
PixelWidth	Total width of all pixels	16
PixelRedWidth	Width of the Red component	5
PixelGreenWidth	Width of the Blue component	6
PixelBlueWidth	Width of the Green component	5
CommandWidth	Width of the Command line	3	(Room for Configure, Fill, Write, Read and None)
CommandDataTimerCount	Additional Clock cycles per Read/Write Op	0	0 is top speed
DelayTimerCount	How many cycles to delay between commands	10000	Could be optimized to less

Ports

Name	Dir	Width	Description	Comment
clock	In	1	Module clock	Tested at 48MHz
reset	In	1	Module reset
command	In	CommandWidth	Command	One of NOP, Configure, Fill Rect, Write Rect, Read Rect
abort	In	1	Stops the current operation
ready	Out	1	LCD is ready for a command
fill_pixel	In	PixelWidth	Pixel value for fill rect
rect_x0	In	CoordinateWidth	Rectangle to be used in commands
rect_x1	In	CoordinateWidth
rect_y0	In	CoordinateWidth
rect_y1	In	CoordinateWidth
pixel_x	Out	CoordinateWidth	Outputs X during Read or Write
pixel_y	Out	CoordinateWidth	Outputs Y during Read or Write
rect_pixel_write	In	PixelWidth	Pixel data to write
rect_pixel_write_valid	In	1	Pixel data is valid
rect_pixel_write_ready	Out	1	Module is ready
rect_pixel_read	Out	PixelWidth	Pixel data read
rect_pixel_read_valid	Out	1	Pixel data is valid
rect_pixel_read_ready	In	1	External module is ready
lcd_db	In/Out	DataWidth	LCD Data
lcd_rd	Out	1	LCD ~Read Enable
lcd_wr	Out	1	LCD ~Read Enable
lcd_rs	Out	1	LCD Data or Command
lcd_cs	Out	1	LCD Chip Select
lcd_id	In	1		What is this, again?
lcd_rst	Out	1
lcd_fmark	Out	1
lcd_blen	In	1	LCD Backlight

Hardware Connection

Hackaday Badge

The LCD is fixed on the board, and the hardware lines are named in the constraints file and presented as top level ports, so connection is easy. Just drop them in.

Invocation

    localparam CoordinateWidth = 9;
    localparam PixelWidth = 16;
    localparam PixelRedWidth = 5;
    localparam PixelGreenWidth = 6;
    localparam PixelBlueWidth = 5;
    localparam CommandWidth = 3;

    reg [ CommandWidth-1:0]   command;
    wire                      ready;

    reg [PixelWidth-1:0]      fill_pixel;

    reg [CoordinateWidth-1:0] rect_x0;
    reg [CoordinateWidth-1:0] rect_x1;
    reg [CoordinateWidth-1:0] rect_y0;
    reg [CoordinateWidth-1:0] rect_y1;

    reg [CoordinateWidth-1:0] pixel_x;
    reg [CoordinateWidth-1:0] pixel_y;

    reg [PixelWidth-1:0]      rect_pixel_write;
    reg                       rect_pixel_write_valid;
    wire                      rect_pixel_write_ready;
    wire [PixelWidth-1:0]     rect_pixel_read;
    wire                      rect_pixel_read_valid;
    reg                       rect_pixel_read_ready;

    lcd l (
            .clock( clock ),
            .reset( reset ),

            .command( command ),
            .ready( ready ),

            .fill_pixel( fill_pixel ),

            .rect_x0( rect_x0 ),
            .rect_x1( rect_x1 ),
            .rect_y0( rect_y0 ),
            .rect_y1( rect_y1 ),

            .pixel_x( pixel_x ),
            .pixel_y( pixel_y ),

            .rect_pixel_write( rect_pixel_write ),
            .rect_pixel_write_valid( rect_pixel_write_valid ),
            .rect_pixel_write_ready( rect_pixel_write_ready ),

            .rect_pixel_read( rect_pixel_read ),
            .rect_pixel_read_valid( rect_pixel_read_valid ),
            .rect_pixel_read_ready( rect_pixel_read_ready ),

            .lcd_db(lcd_db),
            .lcd_rd(lcd_rd),
            .lcd_wr(lcd_wr),
            .lcd_rs(lcd_rs),
            .lcd_cs(lcd_cs),
            .lcd_id(lcd_id),
            .lcd_rst(lcd_rst),
            .lcd_fmark(lcd_fmark),
            .lcd_blen(lcd_blen)
        );

Testing

Tested in lcd_tb.v

Tested on the Hackaday 2019 Badge (ECP5)

LCD Proxy

Implemented to provide something to test the lcd against. Connects to lcd via the 8 ports that would normally go to real hardware.

Implements Fill Rect and Write Buffer into a frame buffer.

Provides debug access to the frame buffer for testing.