Task III: LCD interfacing using 8051 MicrocontrollerAIM/OBJECTIVE:The objective is to interface an output device such as an LCD using 8051 microcontroller.EQUIPMENT REQUIRED: One LCD: LM016L One uC: AT89C51SOFTWARE USED: Proteus ISIS Professional Keil uVision 4 SUMMARY ON DATASHEET:HD44780U is a 16*2 bit LCD device. The input voltage range is from 2.7 to 5.5V.The LCD chip used in here has 14 pins. While Vcc and Vss provide +5V and ground respectively, VEE is used for controlling the contrast. The pin description as listed below:PinSymbolI/ODescription

1Vss-Ground

2Vcc-+5V Supply

3VEE-Controls contrast

4RSIRS=0: Command RegisterRS=1: Data Register

5R/WIR/W=0: WriteR/W=1: Read

6EI/OEnable

7-14DB0-DB7I/OThe 8-Bit Data bus

THEORY:. LCD is fast replacing LED for displaying data as it can display not only numbers unlike LED but can also print out Alphabets and other characters using their ASCII values. Moreover, with the decrease in their prices, there is no moving back for LCDs. An LCD has 2 registers of importance; Data Register and Instruction command register. The RS pin select is used to differentiate between command signal and data signal according to the configuration discussed in Datasheet. R/W pin is used to either write or read the LCD. Enable pin is used to latch the data present at the data pins of the LCD chip. When data is supplied, the enable pin must undergo a high to low transition to latch the data. There are 8 I/O data pins to send and receive information to and from the LCD. RS pin along with R/W pin is used to monitor the Busy flag. When RS=0 along with R/W=1 and if Busy flag status is 1, the LCD wont accept any new information and would carry on its own internal functions.PROCEDURE: The LCD and microcontroller were connected according to Fig 1. They were then connected to the Virtual Terminal. The program was written in Keil and was embedded in the microcontroller. Port 1 of the microcontroller was assigned the pins like Enable, RS and R/W to perform specific functions on the LCD. Port 2 of the microcontroller was connected to the data bus of the LCD for either information or data transfer between the two. Different data inputs were written on to the LCD like Data, Instruction, Numbers and Alphabets and were successfully tested.PROGRAM CODE:ENABLEBIT P1.1// Pin P1.1 connected to Enable of LCDRSBIT P1.0// Pin P1.0 connected to Enable of LCD

DATAPORT EQU P2// Port 2 connected as Data Port of LCD ORG 000MAIN:ACALL DELAY// Call DelayACALL SETUP_SERIAL// Initialize UART at 9600MOV DPTR,#INIT_TEXTACALL SEND_LINE// send string to Serial terminalACALL INIT_LCD// initialize LCDMOV DPTR,#MY_TEXTAGAIN_PRINT:// Print to LCDCLR AMOVC A,@A+DPTRACALL SEND_DATA//Send character to LCDINC DPTRJNZ AGAIN_PRINTMOV DPTR,#DONE_TEXTACALL SEND_LINE//Send string to serial terminal//MOV A,#"J"//ACALL SEND_CHAR HERE:ACALL RCV_CHARCJNE A,#27,NEXT// ASCII ESCAPE=27 DECIMALACALL CLR_LCD//Clear the LCDSJMP HERENEXT:ACALL SEND_DATASJMP HEREWAIT:SJMP WAITCLR_LCD:MOV A,#01HACALL SEND_CMD//Send command to the LCDRETINIT_LCD://Initialization function of LCDMOV A,#38H// INIT 2 LINESACALL SEND_CMDMOV A,#0EH// DISPLAY ON & CURSOR ONACALL SEND_CMDMOV A,#01H//CLEAR LCDACALL SEND_CMDMOV A,#06H//SHIFT CURSOR RIGHTACALL SEND_CMDMOV A,#80H// CURSOR AT LINE1 POSITION n (80H + n)ACALL SEND_CMDRETSEND_CMD:MOV DATAPORT,ACLR RS//Set as instructionACALL ENABLE_RRETSEND_DATA://Function to write the LCDMOV DATAPORT,ASETB RS//Set as DataACALL ENABLE_RRETENABLE_R:CLR ENABLE//ACALL DELAYSETB ENABLEACALL DELAYCLR ENABLE//ACALL DELAYRETDELAY://Delay functionMOV R6,1DEL1:MOV R7,100DEL0:DJNZ R7,DEL0DJNZ R6,DEL1RETSETUP_SERIAL:MOV TMOD,#20H //TIMER1 MODE2(for serial) and TIMER0 MODE2(auto-reload mode for generating clock of ~10KHz for ADC 0808);SET TIMER1 CONFIG.(used for serial comm.)MOV TH1,#-3//9600 BAUDMOV SCON,#50H//8-bit , 1-stop bit , RECEIVE ENABLEDSETB TR1CLR RI // clear RI for the 1st receptionRETRCV_CHAR://Function to receive character from the terminalWAIT2RCV:JNB RI,WAIT2RCVMOV A,SBUFCLR RIRETSEND_CHAR:MOV SBUF,AWAIT2SEND:JNB TI,WAIT2SENDCLR TIRETSEND_LINE:CLR AMOVC A,@A+DPTRACALL SEND_CHARINCDPTRJNZ SEND_LINERETMY_TEXT: DB "NIT RKL",0INIT_TEXT: DB "INITIALIZING....",0DONE_TEXT: DB "DONE",13,"TYPE YOUR TEXT BELOW :-" ,13,13,0END

RESULTS:

Figure 1: Connections btw uC and LCD

Figure 2: LCD is successfully written

CONCLUSION:The LCD was successfully interfaced by using the 8051 microcontroller. Sentences, Numbers and special characters were tested. Even a few instructions were loaded which worked perfectly.7 | Page