LM032L LCD Controller: Hello World!

Introduction

This page is about an old LM032L LCD module from Hitachi. I found an old one and tried to make it work. The module can display 2 lines with 20 characters each. This page will describe how I got the module to work on a PIC 16F84A microcontroller.

The LM032L LCD module

First I had to find the datasheet for the LM032L LCD, which is no big deal when you use Google. The datasheet will show you how to connect the LCD module. It turned out the LM032L has 14 connections: 8 data lines (DB0...DB7), the power supply (Vss,Vdd,Vo) and some additional control lines (RS,RW,E).

So our module uses 8 parallel lines to send data to it. We can also use it with only 4 lines of data, this saves us some I/O lines on the PIC microcontroller. In this 4-bit mode each byte is transmitted in two phases: first the 4 upper bits are transmitted, then the the 4 lower bits. THIS is the approach I will use for my LCD controller: the PIC16F84A only has 13 I/O pins. We can't afford to use 11 of them just to control an LCD module.

The datasheet of the LM032L does not tell us how to control the LCD module. This is because the LM032L uses another chip to do the actual controlling of the LCD module: the HD44780. This HD44780 has its own datasheet and counts no less than 59 pages! The information in this datasheet applies to the LM032L module as well.

Connections of the LM032L module

The LM032L module has 14 connections that can be soldered. The connections are not numbered but you can find the numbering in the datasheet of the LM032L. The image is not very clear but at the left of the module there are 14 soldering contacts, formed by 2 vertical rows with 7 connections each. The numbering #1 starts with the right connection of the last row.

Pin	Vss	Function
#1	Vss	Power Supply 0V
#2	Vdd	Power Supply +5V
#3	Vo	Contrast (0V)
#4	RS	1=data,0=instruction
#5	RW	1=read, 0=write
#6	E	1=enable
#7	DB0	databus A0
#8	DB1	databus A1
#9	DB2	databus A2
#10	DB3	databus A3
#11	DB4	databus A4
#12	DB5	databus A5
#13	DB6	databus A6
#14	DB7	databus A7

The schematic design

The used circuit is very easy. It is the basic implementation of the PIC16F84A: the chip is powered by applying 5 VDC between the VDD and VSS pins. The capacitor C3 will filter out the high frequency noise. The PIC is driven by an external 4 MHz crystal. C1 and C2 are needed to work properly.

The LCD module is connected to the connector J2. The PIC's Ports RB7:RB4 will drive the DB data pins. The ports RB3:RB1 will drive E (Enable), RW (Read/Write) and RS (Instruction/Data). The Vo connection, to regulate the contrast of the module, is connected to the GND (fixed contrast).

The circuit should be powered by a 5 VDC stabilized voltage. You need to add a voltage regulator (7805) and some capacitors if you don't have a stabilized voltage.

PIC Firmware: V1

My software for the PIC is written in High-Tech C Lite (free version). The software will just initialize the LCD and show you the words "Hello World!". My application defines an array of characters containing the String to show on the LCD. A pointer to this array is then passed to the writeString function. This function will transmit the bytes to the LCD module.

/**************************************************** * This sample application for the PIC 16F84A drives * the LM032L LCD module. * * The application uses a 4-bit data bus ****************************************************/ #include <htc.h>; // define crystal speed #define _XTAL_FREQ 4000000 // define names #define RS RB1 // RS word. 0=Instr, 1=Data #define RW RB2 // RW word. 0=write, 1=read #define CE RB3 // CE word. 0=disabled, 1=enabled #define busy RB7 #define MODE_DATA 1 #define MODE_CMD 0 // function prototypes //void write (char data, char mode); void writeFourbits(char data); void writeData(char data); void writeString(char *pMsg); void writeCommand(char data); void LCDbusy(); void LCDinitialize(); void main(); // Initialize the LCD module // Set to 4-bit operation, no cursor void LCDinitialize() { writeCommand(0x28); // busy flag & address writeCommand(0x28); // busy flag & address writeCommand(0x28); // busy flag & address writeCommand(0x06); // cursor move direction writeCommand(0x0C); // LCD enable, cursor off writeCommand(0x01); // clear LCD } // LCDbusy() will wait until the LCD isn't busy void LCDbusy() { TRISB7=1; // put port into input mode RS=0; RW=1; CE=1; while (busy==1); CE=0; TRISB7=0; // put port into output mode } // writeFourBits writes a sequence of 4 bits to the LCD void writeFourbits(char data) { PORTB=(PORTB&0x0F)|data; RW=0; __delay_us(1); CE=1; __delay_us(2); CE=0; __delay_us(3); } // writeCommand writes a character to the LCD void writeData(char data) { RS=MODE_DATA; writeFourbits(data&0xF0); writeFourbits((data&0x0F)<<4); LCDbusy(); } // writeCommand writes a command to the LCD void writeCommand(char data) { RS=MODE_CMD; writeFourbits(data&0xF0); writeFourbits((data&0x0F)<<4); LCDbusy(); } // writeString() will write a String to the LCD void writeString(char *pMsg) { writeCommand(0x01); // clear LCD while(*pMsg!='\0') writeData(*pMsg++); } // Program Main Loop void main () { // define all ports as outputs TRISA=0x00; TRISB=0x00; PORTA=0x00; PORTB=0x00; // initialize the LCD module LCDinitialize(); // define a character array (String) and show on the LCD char lcd[]="Hello World!"; writeString(&lcd); // run an endless loop while (1); }

PIC Firmware: V2

Using this program on a 16F84A microcontroller has a huge disadvantage: the limited RAM space of the 16F84, which is only 68 bytes. Each character in the lcd[] character array will use a single byte of RAM. I see a few possibilities to overcome this problem:

Define the lcd[] array as a constant. The High-Tech C compiler will place this data in the program memory of the PIC, so you won't be wasting RAM working memory. Of course this is only usable when your PIC firmware isn't too large because you lose space for your program.
Use an external EPROM which holds the text strings: There are many small EPROMs that can be controlled with I2C signals. You only need two hardware pins on the microcontroller. Such EPROM can hold thousands of text characters.
The 16F84A has an internal EEPROM flash memory of 64 bytes. It can be used to store data, even if the power is turned off. Many applications don't need this flash memory so you could use it to store some texts.

I have worked out a sample application that demonstrates how you could use the internal EEPROM to store data. This EEPROM will store 4 different string messages. Each message can contain up to 15 characters (The 16th character should always be 0). In this application you can select a message by applying a 5 VDC voltage to the RA0,RA1,RA2 or RA3 input of the 16F84A (note: I didn't illustrate this in the schematic diagram above).

/**************************************************** * This sample application for the PIC 16F84A drives * the LM032L LCD module. * * The application uses a 4-bit data bus * This application demonstrates how to use the EEPROM ****************************************************/ #include <htc.h>; // define crystal speed #define _XTAL_FREQ 4000000 // define names #define RS RB1 // RS word. 0=Instruction,1=Data #define RW RB2 // RW word. 0=write, 1=read #define CE RB3 // CE word. 0=disabled, 1=enabled #define busy RB7 #define MODE_DATA 1 #define MODE_CMD 0 // function prototypes //void write (char data, char mode); void writeFourbits(char data); void writeData(char data); void writeString(char *pMsg); void writeCommand(char data); void LCDbusy(); void LCDinitialize(); void main(); // fill the data __EEPROM_DATA('H','e','l','l','o',' ','W','o'); // Hello World __EEPROM_DATA('r','l','d','!',0,0,0,0); __EEPROM_DATA('H','e','l','l','o',' ','M','o'); // Hello Moon __EEPROM_DATA('o','n','!',0,0,0,0,0); __EEPROM_DATA('b','v','s','y','s','t','e','m'); // bvsystems.be __EEPROM_DATA('s','.','b','e',0,0,0,0); __EEPROM_DATA('1','6','F','8','4','A',' ','D'); // 16F84A Demo __EEPROM_DATA('e','m','o',0,0,0,0,0); // Initialize the LCD module // Set to 4-bit operation, no cursor void LCDinitialize() { writeCommand(0x28); // busy flag & address writeCommand(0x28); // busy flag & address writeCommand(0x28); // busy flag & address writeCommand(0x06); // cursor move direction writeCommand(0x0C); // LCD enable, cursor off writeCommand(0x01); // clear LCD } // LCDbusy() will wait until the LCD isn't busy void LCDbusy() { TRISB7=1; // put port into input mode RS=0; RW=1; CE=1; while (busy==1); CE=0; TRISB7=0; // put port into output mode } // writeFourBits writes a sequence of 4 bits to the LCD void writeFourbits(char data) { PORTB=(PORTB&0x0F)|data; RW=0; __delay_us(1); CE=1; __delay_us(2); CE=0; __delay_us(3); } // writeCommand writes a character to the LCD void writeData(char data) { RS=MODE_DATA; writeFourbits(data&0xF0); writeFourbits((data&0x0F)<<4); LCDbusy(); } // writeCommand writes a command to the LCD void writeCommand(char data) { RS=MODE_CMD; writeFourbits(data&0xF0); writeFourbits((data&0x0F)<<4); LCDbusy(); } // writeString() will write a String to the LCD void writeString(char *pMsg) { writeCommand(0x01); // clear LCD while(*pMsg!='\0') writeData(*pMsg++); } // showMessageFromEEPROM() will show a message from the EEPROM void showMessageFromEEPROM(char msgAdr) { writeCommand(0x01); // clear LCD char currentData; while((currentData=EEPROM_READ(msgAdr++))!='\0') writeData(currentData); __delay_ms(1000); } // Program Main Loop void main () { // define all ports as outputs TRISA=0x00; TRISB=0x00; PORTA=0x00; PORTB=0x00; // initialize the LCD module LCDinitialize(); // run an endless loop while (1) { if (RA0==1) showMessageFromEEPROM(0x00); if (RA1==1) showMessageFromEEPROM(0x10); if (RA2==1) showMessageFromEEPROM(0x20); if (RA3==1) showMessageFromEEPROM(0x30); }; }

My program uses the __EEPROM_DATA macro to assign the texts to the EEPROM memory. Please make sure every call to this macro contains 8 parameters. Use NULL (0) values when you don't need any more characters. My PIC firmware will determine the end of a string by scanning for this NULL character.

Downloads

Here you can download a ZIP containing the High-Tech C source files (for both versions of my firmware) and the data sheets for the LM032L display module.

Download Firmware & Datasheets