Optrex LCD in NIOSOptrex LCD in NIOS

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Optrex LCD introductionOptrex LCD introduction

The Optrex 16207 LCD controller core with Avalon® Interface (LCD controller core) provides the hardware interface and software driver required for a Nios® II processor to display characters on an Optrex 16207 (or equivalent) 16×2-character LCD panel

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Functional DescriptionFunctional Description

E—Enable (output)

RS—Register Select (output)

R/W—Read or Write (output)

DB0 through DB7—Data Bus (bidirectional)

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Source and header filesSource and header files

altera_avalon_lcd_16207_regs.h — This file defines the core's register map, providing symbolic constants to access the low-level hardware.

altera_avalon_lcd_16207.h, altera_avalon_lcd_16207.c — These files implement the LCD controller device drivers for the HAL system library

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Register mapRegister map

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LCD register I/OLCD register I/O

IOADDR_ALTERA_AVALON_LCD_16207_COMMAND(base) Write to command register

IORD_ALTERA_AVALON_LCD_16207_STATUS(base) Read from status register

IOWR_ALTERA_AVALON_LCD_16207_DATA(base, data) IORD_ALTERA_AVALON_LCD_16207_DATA(base) Write to/ Read from data register

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Command wordsCommand words

LCD_CMD_WRITE_DATA = 0x80/* Bits 6:0 hold character RAM address */

LCD_CMD_ONOFF = 0x08, LCD_CMD_ENABLE_DISP = 0x04, LCD_CMD_ENABLE_CURSOR = 0x02, LCD_CMD_ENABLE_BLINK = 0x01/* On/Off command */ LCD_CMD_CLEAR = 0x01/* Clear command */

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Write command word to LCDWrite command word to LCD

static int lcd_write_command(unsigned char * base, unsigned char command)

{ int i = 1000000;/* Wait until LCD isn't busy. */ while (IORD_ALTERA_AVALON_LCD_16207_STATUS(base) &

ALTERA_AVALON_LCD_16207_STATUS_BUSY_MSK) if (--i == 0) return 0; usleep(100); IOWR_ALTERA_AVALON_LCD_16207_COMMAND(base, command); return 1}

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Write data to LCDWrite data to LCD

static int lcd_write_data(unsigned char * base,unsigned char data){int i = 1000000;while (IORD_ALTERA_AVALON_LCD_16207_STATUS(base) &

ALTERA_AVALON_LCD_16207_STATUS_BUSY_MSK) if (--i == 0) return 0;usleep(100);IOWR_ALTERA_AVALON_LCD_16207_DATA(base, data);return 1;}

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LCD coordinates and display LCD coordinates and display addressesaddresses

Display cell in LCD is identified by display address

Address(x,y)= x+colstart[y] x: column y: row colstart[2] = { 0x00, 0x40}

A B C D …

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LCD display bufferLCD display buffer

Display buffer is located in memory, storing the displayed contents on LCD screen

Dynamically updated by software

Keep LCD display in memory, provide a convenient way to read data from LCD

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Data structure of display bufferData structure of display buffer

#define MAX_WIDTH 16#define MAX_HEIGHT 2

struct lcd_buffer_type{ int x,y; // Current display coordinate char buffer[MAX_HEIGHT][MAX_WIDTH]; // Buffer} lcd_buffer;

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Update display bufferUpdate display buffer

When sending command to LCD, corresponding display buffer status also need to be updated

Writing character to LCD

Screen scrolling

Screen clearing

Special character: \t, \b, \n

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Write character to LCDWrite character to LCD

command=LCD_CMD_WRITE_DATA | (x+colstart[y]) Compose write command word, lower 6 bits are the display

address of the character character=<character to be output> lcd_write_command(base,command) // Write command to command register lcd_write_data(base,character)// Write data to data register <Update display buffer>

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Write character to LCDWrite character to LCD

static int lcd_print_char(unsigned char * base, int y, int x, unsigned char c)

{ unsigned char command=0; command=LCD_CMD_WRITE_DATA | (x+colstart[y]);

lcd_write_command(base,command); lcd_write_data(base,c); lcd_buffer.buffer[y][x]=c;}

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Clear ScreenClear Screen

static void lcd_clear_screen(unsigned char * base)

{

int y;

int i,j;

lcd_write_command(base, LCD_CMD_CLEAR);

lcd_buffer.x=0;

lcd_buffer.y=0;

for(i=0;i<MAX_HEIGHT;i++)

{

for(j=0;j<MAX_WIDTH;j++)

{

lcd_buffer.buffer[i][j]=' ';

}

}

}

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Repaint ScreenRepaint Screen

static int lcd_repaint(unsigned char * base){ int i,j; for(i=0;i<MAX_WIDTH;i++) { for(j=0;j<MAX_HEIGHT;j++) { lcd_print_char(base,j,i,lcd_buffer.buffer[j][i]); } }return 1;}

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Scroll ScreenScroll Screen

static int lcd_scroll_up(unsigned char *base){ int i,j; for(i=0;i<MAX_WIDTH;i++) { lcd_buffer.buffer[0][i]=lcd_buffer.buffer[1][i]; lcd_buffer.buffer[1][i]=' '; } lcd_repaint(base); return 1;}

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Control CharactersControl Characters

Special character used to control display format

‘\n’: New line ‘\b’: backspace …

When print control characters on LCD, updating need to be applied to both LCD screen and display buffer

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Handle new line character ‘\n’Handle new line character ‘\n’

Pseudo code: if characer=‘\n’ if ( cursor doesn’t reach the bottom of the screen ) coordinate.y++ coordinate.x=0 else coordinate.x=0 scroll screen up one line

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Handle backspace character ‘\b’Handle backspace character ‘\b’

Pseudo code: if characer=‘\b’ if ( cursor doesn’t located at the start of line ) coordinate.x++ else do nothing

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SummarySummary

JTAR UART on DE2 board Introduction HAL supports Register file and register access Interrupts

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HW2 answer keysHW2 answer keys

1 [a] what is the purpose of I/O on a board Moving information into and out of the board to I/O

devices [b] List five categories of board I/O, with two real-world

examples under each category Networking and communication I/O (wireless & wire

network card) Input(keyboard mouse) Graphic and output I/O(touch screen, CRT) Storage I/O (hard drive, CD ROM) Debugging I/O (BDM, JTAG)

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2 Name and describe the six logical units into which I/O hardware can be classified

Transmission medium Communication port Communication interface I/O controller I/O buses Master processor integrated I/O

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3 In figure 6-26a and b indicate what I/O component fall under what I/O logical unit

Look at page 255 Figure 6-3 a and b

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4 [a] what is the difference between serial and parallel I/O

Serial: data are transferred one bit at a time Parallel: multiple bits simutaneously

[b] Give a real world I/O example of each

Serial: RS-232 Parallel: PCI

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5 [a] What is the difference between simplex, half-duplex and full duplex

Simplex: one way only Half duplex: bidirection, but one direction only at a time Full duplex: bidirection anytime

[b] Indicate which transmission scheme is shown in Figure 6-27a,b,c

Look at Figure 6-4a,b,c

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6 [a] what is asynchronous transfer of serial data Data are transferred intermittently at irregular intervals

[b] Draw a diagram that describes how asynchronous transfer of serial data works

Figure 6-5

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7 The baud rate is A. the bandwidth of the serial interface B. the total number of bits that can be transmitted C. the total number of bits per unit time that can be

transmitted D. None of above

C

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What is the bit rate of a serial interface

A measurement for the data transmission rate

Write the equation

Number of actual data bits per frame/total number of bits per frame* baud rate

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9 [a] what is synchronous transfer of serial data Data transmission is regulated by CPU’s clock

[b] Draw and describe how synchronous transfer of serial data works

Figure 6-6

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10 A UART is an example of a synchronous serial interface

FALSE

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12 [a] What is a serial portcommunication interface connects serial I/O devices and

serial I/O on board [b] Give a real world example of serial port USB port

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[20] How board I/O negatively impact a system’s performance

Slow I/O will make processor waiting for data in most cycles

Fast I/O will not be efficient when combined with a slow CPU

Synchronization between CPU and I/O Strategy for I/O communication (polling<interrupt<DMA)

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21 If there is no mechanism to synchronize the speed differences between I/O devices and the master CPU

A. data will lost B. nothing can go wrong C. the entire system could crush D. A and C only E None of the above

D