8051 Interfacing LCD 16x2

8/17/2019 8051 Interfacing LCD 16x2

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A1.8051 Interfacing:LCD 16x2

Introduction:LCDLiquid Crystal Display(LCDs) provide a cost effective way to put a text output unit for a microcontroller. As

we have seen in the previous tutorial L!Ds or " #e$ments do no have the flexi%ility to display informative

messa$es. &his display has ' lines and can display characters on each line. *onetheless when it is

interfaced with the microcontroller we can scroll the messa$es with software to display information which is

more than characters in len$th.

LCD Internal Controller

Fig 1: LCD Block diagram

&he LCD is a simple device to use %ut the internal details are complex. +ost of the x' LCDs use a Hitachi

HD44780 or a compati%le controller. ,es a micrcontroller is present inside a Liquid crystal display as shown

in fi$ure .


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&he Display Controller ta-es commands and data from a external microcontroller and drivers the LCD panel(LCDP). It ta-es a A#CII value as input and $enerate a patter for the dot matrix. !.$. to display letter A

it ta-es its value 0X42(hex) or 66(dec) decodes it into a dot matrix of /x" as shown in fi$ure '.

Baic Command

&he LCD controller uses 0# and 01 lines alon$ with ! to operate the LCD.

• Resister Select (RS): Determine !eat"er a command#$% & 0' i ent #to et

() t"e di)la*' or act(al data#$%&1' i ent.

• Read/Write $+&0, !rite to t"e LCD. $+&1,$ead from t"e LCD.

&he commonly used instructions are shown in the instruction set %elow. 2%serve the Bit names: I/D, , D,

C etc at the %ottom of instruction set to decode the instructions completely.

• Clear Di)la*

• C(ror -ome

• %et ntr* /ode

• Di)la* ono control

• C(rordi)la* "ift

• F(nction %et


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• $ead B(* Flag

• Data $ead

• Data +rite

Intr(ction %et

HD44780U based instruction set

Instruction

Code Description

R

S

R/

W

B

7

B

B

!

B

4

B

"

B

#

B

$

B

0

Clear di)la* 0 0 0 0 0 0 0 0 0 1Clear di)la* and ret(rn c(ror to t"e

"ome )oition #addre 0'.

C(ror "ome 0 0 0 0 0 0 0 0 1 3

$et(rn c(ror to "ome )oition. Alo

ret(rn di)la* 4eing "ifted to t"e

original )oition. DD$A/ content

remain (nc"anged.

ntr* mode

et0 0 0 0 0 0 0 1

I

D%

%et c(ror moe direction #ID',

)ecie to "ift t"e di)la* #%'. 7"ee

o)eration are )erformed d(ring data

read!rite.

Di)la*

ono

control

0 0 0 0 0 0 1 D C B

%et ono of all di)la* #D' c(ror

ono #C' and 4link of c(ror )oition

c"aracter #B'.

C(rordi)la

* "ift

0 0 0 0 0 1 %

C

$

L

3 3 %et c(ror9moe or di)la*9"ift #%C'

"ift direction #$L'. DD$A/ content


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remain (nc"anged.

F(nction et 0 0 0 0 1DL

; F 3 3%et interface data lengt" #DL' n(m4erof di)la* line #;' and c"aracter font

#F'.

$ead 4(*

$A/DD$A/

addre

$ead 4(* $A/ or

DD$A/

1 0 +rite Data +rite data to C>$A/ or DD$A/.

+rite

C>$A/ or

DD$A/

1 0 +rite Data +rite data to C>$A/ or DD$A/.

Instruction bit na%es &

I/D 3 4 5 decrement cursor position 5 increment cursor position6

3 4 5 no display shift 5 display shift6

D 3 4 5 display off 5 display on6

C 3 4 5 cursor off 5 cursor on6

B 3 4 5 cursor %lin- off 5 cursor %lin- on 6

/C 3 4 5 move cursor 5 shift display6

!/L 3 4 5 shift left 5 shift ri$ht6

DL 3 4 5 73%it interface 5 83%it interface6

" 3 4 5 98 or 9 duty ( line) 5 9 duty (' lines)6

# 3 4 5 /8 dots 5 /4 dots6

B# 3 4 5 can accept instruction 5 internal operation in pro$ress.

LCD ?;I7


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Let ( look at a )in diagram of a commerciall* aaila4le LCD like 'HD$# !"ic" (e

a HD44780 controller and t"en decri4e it o)eration.

All the pins are identically to the lcd internal controller discussed a%ove

I U*B+R ,UC-I.

1 >ro(nd

2 @CC

Contrat ad(tment #@'

$egiter %elect #$%'. $%&0: Command $%&1: Data

5 $ead+rite #$+'. $+&0: +rite $+&1: $ead


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6 Clock #na4le'. Falling edge triggered

Bit 0 #;ot (ed in 94it o)eration'

8 Bit 1 #;ot (ed in 94it o)eration'

Bit 2 #;ot (ed in 94it o)eration'

10 Bit #;ot (ed in 94it o)eration'

11 Bit

12 Bit 5

1 Bit 6

1 Bit

15 Back9lig"t Anode#E'

16 Back9Lig"t Cat"ode#9'


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Interfacing LCD !it" 8051

LCD can 4e interfaced !it" t"e 8051 micrcontroller in t!o mode 8 4it and 4it. Let (

Interface it in 8 4it mode rt.

8 4it /ode

4ectie

g LCD di)la*

&here is lot of stuff that can %e done with the LCDs to start with we will simple display a couple of strin$s on

the ' lines of the LCD as shown in the ima$e.

%c"ematic Dicri)tion• Data ines In t"i mode all of t"e 8 dataline DB0 to DB are connected from

t"e microcontroller to a LCD mod(le a "o!n t"e c"ematic.

• Control ines1 7"e $% $+ and are control line a dic(ed earlier.

• o2er 3 contrast:A)art from t"at t"e LCD "o(ld 4e )o!ered !it" 5@

4et!een I #(CC) and I $(5nd). I " i t"e contrat )in and i o(t)(t of

center terminal of )otentiometer#oltage diider' !"ic" arie oltage 4et!een 0

to 5 to ar* t"e contrat.

• Bac6li5t 7"e I; 15 and 16 are (ed a 4acklig"t. 7"e led 4acklig"t can 4e

)o!ered t"ro(g" a im)le c(rrent limiting reitor a !e do !it" normal led.


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%c"ematic

Code

As with all the interfaces to simplify thin$ we have separated code into two files main.c and lcd;8;%it.c. ,ou

may $o throu$h the tools setup tutorial on confi$urin$ the code.

&he main.c is very simple it includes the standard li%rary files. &hen it uses several functions from the

lcd;8;%it.c file to set up and display messa$es. As you can see it ma-es thin$s very simple when the li%raries

are well written. 1e will discuss the implementation while discussin$ the lcd;8;%it.c file.

http://exploreembedded.com/wiki/8051_ToolsSetuphttp://exploreembedded.com/wiki/8051_ToolsSetuphttp://exploreembedded.com/wiki/8051_ToolsSetup


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The main fle main.c

/* Reg51.h contains the defnition of all ports and SFRs */

#include

#include "lcd.h" //Xplore labz LCD library#include "delay.h" //Xplore Labz Delay library

/* start the main program */

void main!

/* Initilize the lcd before displaying any thing on the lcd */

LCD$ni%!&

/* Display "hello !orld" on first line*/

LCDDi'play(%ring"hello) *orld"!&

/*o to second line and display "good morning" */

LCD+o,oLine,*o!&

LCDDi'play(%ring"good morning"!&

*hile1!&

-

lcd_8_bit.c: 8 bit lcd library fle

7"e lcd989bit:c conit of ario( f(nction t"at are reG(ired to initialiHe and (e t"eLCD. Let ( look at fe! im)ortant line and f(nction. Speci;


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are shown in the fi$ure

• te)1: %end t"e I command to LCD.

•

te)2: %elect t"e Control $egiter 4* making $% lo!.

• te): %elect +rite o)eration making $+ lo!.

• te): %end a -ig"9to9Lo! )(le on na4le I; !it" ome dela*(.

void LCDCmd6ri%e char cmd!

da%abu'3cmd& // Send the command to ()D

r'34& // Select the )ommand Register by plling RS (+%

r*34& // Select the %rite +peration by plling R% (+%

en31& // Send a ,igh-to-(o! #sle at &nable #in

delayu'14!&

en34&

delaym'1!&

-


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2' id LCD%Data*+ite( cha+ dat) &his function sends a character to %e displayed on LCD in the followin$

steps.

• te)1: %end t"e c"aracter to LCD.

• te)2: %elect t"e Data $egiter 4* making $% "ig".

• te): %elect +rite o)eration making $+ lo!.

• te): %end a -ig"9to9Lo! )(le on na4le I; !it" ome dela*(.

&he timin$s are similar as a%ove only chan$e is that ! is made hi$h.

void LCDDa%a6ri%e char da%!

da%abu'3da%& // Send the data to ()D

r'31& // Select the Data Register by plling RS ,I,

r*34& // Select the %rite +peration by plling R% (+%

en31& // Send a ,igh-to-(o! #sle at &nable #in

delayu'14!&

en34&

delaym'1!&

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' id LCD%Init()

Loo-in$ at the instruction set of the LCD controller we can initiali


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7"e remaining code i lited 4elo!. Jo( co(ld o4ere t"at t"e 4aic f(nction to read

data and !rite !rite command are (ed exteniel* and entire li4rar* i 4(ilt ()on

t"em. 7"ere are alo ot"er f(nction t"at are (ed to di)la* n(m4er etc in t"e lcd

li4rar* le.

Kincl(dereg51."M Kincl(de Ndela*."N Kincl(de Nlcd."N Kdene data4( 2 LCD

data4( connected to $72 4it r& 0O0, $egiter elect )in connected to 0.0

4it r!& 0O1, $ead +rite )in connected to 0.1 4it en& 0O2, na4le )in

connected to 0.2 3 16x2 LCD %)ecication 3 Kdene LCD/axLine 2 Kdene

LCD/axC"ar 16 Kdene Linene 0x80 Kdene Line7!o 0xc0 Kdene Blank%)ace P P

oid LCDInit#' Q dela*(#5000', LCDCmd+rite#0x8', LCD 2line 53 matrix

LCDCmd+rite#0x0', Di)la* ; c(ror ; Blinking o LCDCmd+rite#0x01', Clear

t"e LCD LCDCmd+rite#0x80', C(ror to Firt line Firt oition R oid

LCDCmd+rite# c"ar cmd' Q data4(&cmd, %end t"e command to LCD r&0, %elect

Command $egiter 4* )(lling $% L+ r!&0, %elect +rite )eration 4* )(lling $+

L+ en&1, %end a -ig"9to9Lo! (le at na4le in dela*(#10', en&0,

dela*m#1', R oid LCDData+rite# c"ar dat' Q data4(&dat, %end t"e data to

LCD r&1, %elect t"e Data $egiter 4* )(lling $% -I>- r!&0, %elect t"e +rite

)eration 4* )(lling $+ L+ en&1, %end a -ig"9to9Lo! (le at na4le in

dela*(#10', en&0, dela*m#1', R oid LCD>o7oSJ#c"ar ro! c"ar col' Q c"ar )o,

if#ro!LCD/axLine' Q )o& Linene T #ro! 6', take t"e line n(m4er ro!09

M)o&0x80 ro!19M)o&0xc0 if#colLCD/axC"ar' )o& )oEcol, take t"e c"ar

n(m4er no! )o )oint to SJ )o LCDCmd+rite#)o' R R oid

LCDDi)la*%tring#c"ar 3tring)tr' Q !"ile#3tring)tr' LCDData+rite#3tring)trE

E', R

4it /ode

%c"ematic

&here are followin$ differences in 7 %it mode.

• nl* data line D to D are (ed a "o!n in t"e c"ematic 4elo!.

• In code !e need to end t"e command to elect 4it mode a "o!n in t"e

intr(ction et a4oe.


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&he main pro$ram remains exactly as in 8 %it mode we simply include the $cd%4%&it'c to wor- in 7 %it mode.

&he important and required code is listed %elow

CodeKincl(dereg51."M Kincl(de Ndela*."N Kincl(de Nlcd."N Kdene data4( 0 LCD

data4( connected to $70 4it r& data4(O0, $egiter elect )in connected to

0.0 4it r!& data4(O1, $ead +rite )in connected to 0.1 4it en& data4(O2,

na4le )in connected to 0.2 3 16x2 LCD %)ecication 3 Kdene LCD/axLine 2

Kdene LCD/axC"ar 16 Kdene Linene 0x80 Kdene Line7!o 0xc0 Kdene

Blank%)ace P P oid LCDInit#' Q dela*(#5000', LCDCmd+rite#0x02', InitiliHe t"e LCD


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in 4it /ode LCDCmd+rite#0x28', LCDCmd+rite#0x0', Di)la* ; c(ror ;

LCDCmd+rite#0x01', Clear t"e LCD LCDCmd+rite#0x80', C(ror to Firt line Firt

oition R oid LCDCmd+rite# c"ar cmd' Q data4(cmd = 0xf0', %end t"e

-ig"er ;i44le r&0, %elect t"e Command $egiter 4* )(lling $% L+ r!&0, %elect

t"e +rite )eration 4* )(lling $+ L+ en&1, %end a -ig"9to9Lo! (le at na4le in

dela*(#1', en&0, dela*(#10', !ait for ome time data4(#cmd' =0xf0', %end t"e Lo!er ;i44le r&0, %elect t"e Command $egiter 4* )(lling $% L+

r!&0, %elect t"e +rite )eration 4* )(lling $+ L+ en&1, %end a -ig"9to9Lo!

(le at na4le in dela*(#1', en&0, dela*m#1', R oid LCDData+rite# c"ar

dat' Q data4(dat = 0xf0', %end t"e -ig"er ;i44le r&1, %elect t"e Data $egiter

4* )(lling $% -I>- r!&0, %elect t"e +rite )eration 4* )(lling $+ L+ en&1, %end

a -ig"9to9Lo! (le at na4le in dela*(#1', en&0, dela*(#10', !ait for ome

time. data4(#dat ' = 0xf0', %end t"e Lo!er ;i44le r&1, %elect t"e Data

$egiter 4* )(lling $% -I>- r!&0, %elect t"e +rite )eration 4* )(lling $+ L+

en&1, %end a -ig"9to9Lo! (le at na4le in dela*(#1', en&0, dela*m#1', R

oid LCDDi)la*%tring#c"ar 3tring)tr' Q !"ile#3tring)tr'

LCDData+rite#3tring)trEE', R oid LCD>o7oLine7!o#' Q LCDCmd+rite#Line7!o', /oe t"e C(ror to %econd line R

Downloads=&he code is $iven for 7 and 8 %it modes with and without %usy >la$=

8051ILCDI7(torialICode.Hi)

8051 Interfacing LCD 16x2

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