How to Interface LCD with LPC2148 ARM7 Development Board
The ARM7 LPC2148 Development Board is specifically designed to help students to master the required skills in the area of embedded systems. The kit is designed in such way that all the possible features of the microcontroller will be easily used by the students. The kit supports in system programming (ISP) which is done through serial port.
NXP’s ARM7 (LPC2148), ARM Development Kit is proposed to smooth the progress of developing and debugging of various designs encompassing of High speed 32-bit Microcontrollers.
LCD (Liquid Crystal Display)
Liquid Crystal Display also called as LCD is very helpful in providing user interface as well as for debugging purpose. A liquid crystal display (LCD) is a flat panel display that uses the light modulating properties of liquid crystals (LCs). LCD Modules can present textual information to user.
Interfacing LCD
Fig. 1 shows how to interface the LCD to the microcontroller. The 2×16 character LCD interface card supports both modes 4-bit and 8-bit interface, and also a facility to adjust contrast through the trim pot. In 4-bit interface 7 lines needed to create a 4-bit interface; 4 data bits (D0 – D3), three control lines, address bit (RS), read/write bit (R/W), and the control signal (E).
Interfacing 4 bit LCD with LPC2148
We now want to display a text in LPC2148 Development Board by using 4 bit LCD module.
The ARM7 LPC2148 Development Board has seven numbers of LCD connections are needed to create 4-bit interface; connected with 4 data bits (P0.19 – P0.22, D4-D7), address bit (RS-P0.16), read/write bit (R/W-P0.17) and control signal (E-P0.18) to make LCD display.
Pin Assignment with LPC2148
Circuit Diagram to Interface 4 bit LCD with LPC2148
Source Code
The Interfacing 4 bit LCD with LPC2148 program is very simple and straight forward, which display a text in 2 X 16 LCD module using 4 data lines only. Some delay is occurring when a single command / data is executed.
C Program to display a text in 4 bit LCD using LPC2148
***************************************************************************************
Title : Program to 4 bit LCD display
***************************************************************************************
#include
#define RS 0x10000
#define RW 0x20000
#define EN 0x40000
void lcd_cmd (unsigned char);
void lcd_data (unsigned char);
void lcd_initialize (void);
void lcd_display (void);
void LCD4_Convert(unsigned char);
const unsigned char cmd[4] = {0x28,0x0c,0x06,0x01}; //lcd commands
unsigned char msg[] = {">PS-Development 2148<"}; //msg
unsigned char msg1[]= {":: LCD Demo! ::"}; //msg1
void delay(unsigned int n)
{
unsigned int i,j;
for(i=0;i<n;i++)
{
for(j=0;j<12000;j++)
{;}
}
}
//----------------------------------
// LCD Command Send
//----------------------------------
void lcd_cmd(unsigned char data)
{
IOCLR0 |= RS; //0x1000; //RS
IOCLR0 |= RW; //0x2000; //RW
LCD4_Convert(data);
}
void lcd_initialize(void)
{
int i;
for(i=0;i<4;i++)
{
IOCLR0 = 0xF << 19; //IOCLR 0/1
lcd_cmd(cmd[i]);
delay(15);
}
}
//----------------------------------
// LCD Data Send
//----------------------------------
void lcd_data (unsigned char data)
{
IOSET0 |= RS; //0x1000; //RS
IOCLR0 |= RW; //0x2000; //RW
LCD4_Convert(data);
}
//----------------------------------
// LCD Display Msg
//----------------------------------
void lcd_display (void)
{
char i;
/* first line message */
lcd_cmd(0x80);
delay(15);
i=0;
while(msg[i]!='\0')
{
delay(5);
lcd_data(msg[i]);
i++;
}
delay(15);
/* second line message */
lcd_cmd(0xc0);
delay(15);
i=0;
while(msg1[i]!='\0')
{
delay(5);
lcd_data(msg1[i]);
i++;
}
delay(15);
}
void LCD4_Convert(unsigned char c)
{
if(c & 0x80) IOSET0 = 1 << 22; else IOCLR0 = 1 << 22;
if(c & 0x40) IOSET0 = 1 << 21; else IOCLR0 = 1 << 21;
if(c & 0x20) IOSET0 = 1 << 20; else IOCLR0 = 1 << 20;
if(c & 0x10) IOSET0 = 1 << 19; else IOCLR0 = 1 << 19;
IOSET0 = EN; //0x4000; //EN
delay(15);
IOCLR0 = EN; //0x4000; //EN
if(c & 0x08) IOSET0 = 1 << 22; else IOCLR0 = 1 << 22;
if(c & 0x04) IOSET0 = 1 << 21; else IOCLR0 = 1 << 21;
if(c & 0x02) IOSET0 = 1 << 20; else IOCLR0 = 1 << 20;
if(c & 0x01) IOSET0 = 1 << 19; else IOCLR0 = 1 << 19;
IOSET0 = EN; //0x4000; //EN
delay(15);
IOCLR0 = EN; //0x4000; //EN
}
void main()
{
PINSEL1 = 0; //Configure P0.16 - P0.31 as GPIO
IODIR0 = 0xFF << 16; //Configure Pins P0.16 - P0.22 as Output Pins
lcd_initialize(); //Initialize LCD!
lcd_display(); //Display Message in LCD
while(1);
}
To compile the above C code you need the KEIL software. They must be properly set up and a project with correct settings must be created in order to compile the code. To compile the above code, the C file must be added to the project.
In Keil, you want to develop or debug the project without any hardware setup. You must compile the code for generating HEX file. In debugging Mode, you want to check the port output without microcontroller Board.
The Flash Magic software is used to download the hex file into your microcontroller through UART0.
Testing the LCD Module with LPC2148
Give +3.3V power supply to LPC2148 Development Board; the LCD is connected with microcontroller LPC2148 Development Board. When the program is downloading into LPC2148 in DevelopmentBoard, the screen should show the text messages.
If you not reading any text from LCD, then you just check the jumper connections & adjust the trim pot level. Otherwise you just check it with debugging mode in Keil. If you want to see more details about debugging just see the videos in below link.
☞How to Create & Debug a Project in Keil.
General Information
☞For proper working use the components of exact values as shown in Circuit file. Wherever possible use new components.
☞Solder everything in a clean way. A major problem arises due to improper soldering, solder jumps and loose joints.
☞Use the exact value crystal shown in schematic.
☞More instructions are available in following articles,
