Numeric LCD Display - Serial, Expandable - Sunrom Technologies

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Document: Datasheet Date: 28-Sep-12 Model #: 1129 Product’s Page: www.sunrom.com/p-1205.html
Numeric LCD Display - Serial, Expandable
Many products require a Liquid Crystal
Display (LCD) Interfaced to a
microcontroller (MCU). These Numeric
LCDs comsume very little power and ideal
for battery operation. It uses serial input
clock data and its expandable to multiple
displays. It uses just four microcontroller
pins. We provide sample code for
AT89S52 in C language. Can be easily be
adapted to other compilers for other MCU
targets.
Although LCDs are initially more complex
to get operational, they are the lowest
cost displays and require the lowest
number of I/O pins of all glass LCDs.
Since we provide ready to compile source
code, it becomes very easy to get a demo
operation within minutes. The last page of
this datasheet mentions everything from
schematic, operation and sample code to
get started.
The result is an excellent low cost
combination and a starting point for many
products.
The LCD display uses just four microcontroller pins and can drive almost unlimited numbers of
display with cascading and thus expanding as many displays required.

Pin Configuration
PIN# Name Details
GND Ground Ground of Power
+V + Power 3-5V Power input
CLK Clock Serial Clock
LAT Latch Latching of data to output
DAT Data Serial data input
COM LCD Common Common signal of LCD Display
Next Display
if required
DISPLAY DATA
FROM MCU
Operation
The MCU is required to drive the LCD pins with 50% square waves of 20ms time(10ms High, 10ms
Low). Each segment on this LCD is connected to the COM backplane and a separate pin. When a
pin is driven in phase with the COM pin, the corresponding LCD segment gets zero voltage, and is
off. When a pin is driven in reverse of the COM pin, the corresponding segment gets an alternating
voltage, and lights up.
The 10ms interrupt routine in microcontroller is called periodically to invert all pins of the LCD to
generate the 50% square wave.
1 Frame = 20 MiliSecond = 50 Hz refresh rate
10ms COM pin High
10ms COM pin Low
Segment is phase with
COM pin, will become
OFF
Segments out of phase
with COM pin will
become ON
Once COM pin is set, a function is called will serially outputs all status of segments. If the segment
is in phase to COM pin they become OFF. And Segments which are made out of phase to COM pin
becomes on.
We provide a detailed commented source code to drive the LCD. See last pages of document.
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Register Mapping
Each display has four serial addressable 8 bit registers. You can shift in data through clock pulses
and make latch pulse to affect the output after all 32 bits(4x8 bits) are clocked in.
Register 3,Misc
Register2,DISPLAY1 Register1,DISPLAY2 Register0, DISPLAY3
Bit Register3, Misc Register2, Disp# #1 Register1, Disp#2 Register0, Disp#3
7 K segment(for 1) DP1
DP2
DP3
6 X 1E
2E
3E
5 Y 1D
2D
3D
4 ^ 1C
2C
3C
3 ~ 1G
2G
3G
2 LOWBAT 1F
2F
3F
1 COL 1A
2A
3A
0 Not used 1B
2B
3B
Cascading multiple display for expansion
Can drive multiple displays easily. Cascading multiple display is easy, One side output goes to
output of next display.
No extra IO from MCU is required. Only software expansion is required,
Provision is given in sample code.
MCU
3
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Your Source for Embedded Systems
Visit us at www.sunrom.com

Dimensions
4
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Sample Application – AT89S52
Th sample code on following page shows how to drive the display serially using AT89S52 controller.
VCC
C8
10uF 16V
R1
10K
+
39
38
37
36
35
34
33
32
1
2
3
4
5
6
7
8
31
9
U2
AT89S52
P0.0/AD0
P0.1/AD1
P0.2/AD2
P0.3/AD3
P0.4/AD4
P0.5/AD5
P0.6/AD6
P0.7/AD7
P1.0/T2
P1.1/T2EX
P1.2
P1.3
P1.4/SS
P1.5/MOSI
P1.6/MISO
P1.7/SCK
EA/VPP
RST
GND
20
VCC
VCC 40
XTAL1
19
C1
100n
P2.0/A8
P2.1/A9
P2.2/A10
P2.3/A11
P2.4/A12
P2.5/A13
P2.6/A14
P2.7/A15
10
P3.0/RXD
P3.1/TXD 11
12
P3.2/INT0
13
P3.3/INT1
14
P3.4/T0
15
P3.5/T1
16
P3.6/WR
17
P3.7/RD
XTAL2
18
21
22
23
24
25
26
27
28
PSEN 29
ALE/PROG 30
Y1
VCC
1
2
3
4
5
6
S1
Sunrom Numeric LCD Model#1129
GND
+V
CLK
LAT
DAT
COM
A
A
A
^ ~
1 2 3
X K F
B F
B F
Y
LOBAT
K
DP1
E
D
G
C
DP2
COL
E
D
G
C
DP3
E
D
G
C
B
C9
33p
11.0592
C10
33p
The code is in C language and can be adapted to any microcontroller easily.
The code can be compiled from below pages (Compiler is Keil C51)
At power up, test function lits up all segments for 5 seconds.
During run time the MCU displays a
integer which increments every
second and places a decimal point
to 2 nd digit.
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*
Author: Sunrom Technologies http://www.sunrom.com
Date: 28th Sep 2012
Hardware Model: Numeric LCD Display Model 1129
Compiler: Keil C51
Shows demo how to control the LCD serially
*/
#include
#include
#include
// Hardware Inteface to MCU
#define CLOCK P2_0
#define LATCH P2_1
#define SDATA P2_2
#define COM P2_3
#define TIMER0_COUNT 0xDC11 /* 10000h - ((11,059,200 Hz / (12 * FREQ)) - 17) */
#define NUMBER_OF_REGISTERS 4
unsigned char digits[NUMBER_OF_REGISTERS]; // we will seperate a integer and
use this variable to store seperated digits
unsigned int count; // we will create a count variable and make it go from 0 to
9999
unsigned char cflag;
// This array has values as to which segment becomes on for a digit from 0 to 9
code unsigned char SegmentMapping[12] =
{
119, //0
17, //1
107, //2
59, //3
29, //4
62, //5
126, //6
19, //7
127, //8
63, //9
0x00, //10: All OFF
0x80 //11: Special mapping for only 1 segment of display
};
/*=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Delay x Milisecond
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*/
void delay_ms(unsigned int x) // delays x msec (at fosc=11.0592MHz)
{
unsigned char j=0;
while(x-- > 0)
{
for (j=0; j

void shift_data(unsigned char one_zero ){
unsigned char i,j;
unsigned char temp;
for(j=0;j1;
CLOCK=1;CLOCK=0; // Clock bit into register
}
}
LATCH=1;
LATCH=0; // latch out data in registers
/*=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Create AC waveform by toggling COM out and cflag variable.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*/
void AC_shift_data(){
if (cflag==1){
COM=1;
shift_data(1);
cflag=0;
}
else
{
COM=0;
shift_data(0);
cflag=1;
}
}
/*=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=void
timer0_initialize (void);
This function enables TIMER 0. TIMER 0 generates a synchronous interrupt
once every 100Hz.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*/
void timer0_initialize (void)
{

}
EA = 0; /* disable interrupts */
TR0 = 0; /* stop timer 0 */
TMOD &= ~0x0F; /* clear timer 0 mode bits */
TMOD |= 0x01; /* put timer 0 into 16-bit no prescale */
TL0 = (TIMER0_COUNT & 0x00FF);
TH0 = (TIMER0_COUNT >> 8);
PT0 = 0; /* set low priority for timer 0 */
ET0 = 1; /* enable timer 0 interrupt */
TR0 = 1; /* start timer 0 */
EA = 1; /* enable interrupts */
/*=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=static
void timer0_isr (void);
This function is an interrupt service routine for TIMER 0. It should never
be called by a C or assembly function. It will be executed automatically
when TIMER 0 overflows.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*/
void timer0_isr (void) interrupt 1
{
/*=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Stop Timer 0, adjust the timer 0 counter so that
we get another interrupt in 10ms, and restart the
timer.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*/
TR0 = 0; /* stop timer 0 */
TL0 = TL0 + (TIMER0_COUNT & 0x00FF);
TH0 = TH0 + (TIMER0_COUNT >> 8);
TR0 = 1; /* start timer 0 for next cycles*/
AC_shift_data(); // Create AC waveform
}
/*=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
This function breaks apart a given integer into separete digits
and writes them to the display array i.e. digits[]
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*/
void seperate_digits()
{
unsigned char i=0;
unsigned char j;
unsigned int num;
num = count;
while(num)
{
digits[i]=num%10;
i++;
num=num/10;
}
for(j=i;j

void test_display_mode()
{
unsigned char i;
unsigned char x=250; // 20 ms per frame x 250 should give us 5 sec of display
while(x>0)
{
/////////////////////////
COM = 1;
// The common pin of LCD
for(i=0; i