Text LCD

Pin number	TextLCD pins	mbed pins
1	GND	0V
2	VCC	3.3V
3	VO	0V, via 1k resistor
4	RS	p15
5	RW	0V
6	E	p16
7	D0	not connected
8	D1	not connected
9	D2	not connected
10	D3	not connected
11	D4	p17
12	D5	p18
13	D6	p19
14	D7	p20

jim hamblen

# 12 Sep 2010

Photo shows different mbed pins hooked to LCD than example code and wiring table. Use wiring table!

jim hamblen

# 12 Sep 2010

Here is another code example using other LCD functions (clear screen and locate) and a timer to display elapsed time:

include "mbed.h"
include "TextLCD.h"

TextLCD lcd(p10, p12, p15, p16, p29, p30); rs, e, d0-d3 Timer t;

int main() { Start timer t.start(); Clear LCD Screen lcd.cls(); wait(1); Print to LCD on first line lcd.printf("Hello LCD World!\n"); while (1) { Move cursor to start of second display line lcd.locate(0,1); Print elapsed time from timer on LCD lcd.printf("%e sec", t.read()); wait(.2); } }

jim hamblen

# 12 Sep 2010

Sorry about the mess in last comment - looked OK in edit window. Preview does not seem to work right in my browser

#include "mbed.h"
#include "TextLCD.h"

TextLCD lcd(p10, p12, p15, p16, p29, p30); // rs, e, d0-d3
Timer t;

int main() {
// Start timer
    t.start();
// Clear LCD Screen
    lcd.cls();
    wait(1);
// Print to LCD on first line
    lcd.printf("Hello LCD World!\n");
    while (1) {
// Move cursor to start of second display line
        lcd.locate(0,1);
// Print elapsed time from timer on LCD
        lcd.printf("%e sec", t.read());
        wait(.2);
    }
}

jim hamblen

# 17 Sep 2010

It is also possible to download eight custom character designs to the HD44780 LCD controller chip. There are numerous articles on the web and even web applications to draw characters and generate the character data. One such character design application is http://www.quinapalus.com/hd44780udg.html. The data sheet describes the download process to define new characters.

Update: Here is some mbed code to load new characters: http://mbed.org/users/DimiterK/notebook/custom-characters-on-hd44780/

T L

# 22 Sep 2010

Just wondering if there's any reason that the specific pins used in the wiring diagram example are used? Can any pins be used for any of the lines. E.g. just use pins 15 to 20 for example?

Bob Dring

# 27 Sep 2010

Having problems with an LCD? Notes from my first time use with a 16x2 unit.

My LCD needs 5V supply (Mbed pin 39)others might be 3.3V The LED backlight needs no current limiting resistor when run from the rated voltage. The contrast potentiometer resistor is required. The SIL connector type of display mates with a breadboard well. The DIL type needs an adapter or cable. The SIL connector pin numbering is weird. 14,13,12,11,10,9,8,7,6,5,4,3,2,1,16,15 (L to R display side) The connections used by this software are E,RS,D4,D6,D7 with R/-W permanently connected to VSS. Where the LCD software documentation mentions signal D0 it really connects to LCD pin D4, D1->D5,D2->D6 and D3->D7 Diagnostic check: If you have power connected correctly to the LCD and a Contrast pot set at one of the extremes, The LCD should show a display of 7 x 5 pixel blocks on the first line. If you don't get this the software cannot display anything.

joby antony

# 02 Oct 2010

I had tuff time to make this working as I connected 3.3V vcc later I realized it needs to be +5 V dc (pin 39) !!!!!

jim hamblen

# 04 Oct 2010

Some LCDs are 3.3V and some are 5V. The older ones tend to be 5V. The datasheet for the exact LCD module can be hard to find if you have an old one. If you buy a new one, they typically have the info on the power supply needed available in the data provided at the website. They all have the same controller chip and you can find that datasheet, but it can be 3.3V or 5V. If you hook up a 5V module to 3.3V, the LCD display will just be blank. And if you hook up the backlight - some need the resistor!

Steve D

# 05 Oct 2010

Having great problems with this.

I have compiled and run the code, rewired and replaced both the MBED and my LCD controller.

For some reason am unable to get any Hello World appearing and I really do not even know what to try anymore.

Any suggestions would be great.

Thanks!

Steve D

# 05 Oct 2010

So. Apparently my pot for contrast was bad. Make sure you check that!! The code does work.

Oliver Ryan

# 07 Oct 2010

Is it possible to run a 40x4 LCD with the TextLCD.h? I don't see it mentioned. Thanks.

Peter Lelie

# 25 Oct 2010

I just uploaded a modified version of the TextLCD library to be able to support ST7036 based displays (like, for example, the DOGM162x-A). I know that a better solution would be to merge this into the original library, but haven't got the time to do this right now.

Please do a search for ST7036 or see http://mbed.org/users/leliep/libraries/TextLCD_ST7036/lgsmve

Oscar van der Aar

# 28 Oct 2010

Oliver Ryan wrote:

Is it possible to run a 40x4 LCD with the TextLCD.h? I don't see it mentioned. Thanks.

a 40x4 is infact a dual 40x2 display it contains two enable lines: E1 and E2. the datasheet of eg. the everboquet MC4004A is on this page: http://www.farnell.com/datasheets/302399.pdf. You have to adapt the progamm code! I'm using this display and i'm adapting the code. When its finished i will post it!

Jelmer Bruggink

# 17 Nov 2010

Hello,

i'm trying to make reading back from the display work, but am having a hard time figuring this out, i know how it works, and doing it manually(manual enable after putting whole display full with text and then putting it in read mode) does work, but when i try to let the mBed doe it, it doesn't work. anyone has any idea?

Arwin Vosselman

# 19 Nov 2010

Jelmer Bruggink wrote:

i'm trying to make reading back from the display work, but am having a hard time figuring this out, i know how it works, and doing it manually(manual enable after putting whole display full with text and then putting it in read mode) does work, but when i try to let the mBed doe it, it doesn't work.

Perhaps you should tell what you have done so far. People might be able to help you easier that way.

Eduard Sjoukes

# 22 Nov 2010

i've got a Optrex LCD (DMC20481 NY-LY-ABE) with a different timing. The enable puls has to be at least 75us instead of 40us and the clear screen command takes 3ms instead of 1.64ms. So i alter the TextLCD libary files on those points into a new OptrexLCD libary. I shall post this libary soon.

Eric Wieser

# 23 Nov 2010

Your wiring diagram contradicts the comments in your code!

Simon Ford

# 23 Nov 2010

Thanks! Fixed.

Dominique Bultez

# 23 Nov 2010

Hi Simon,

I am using this TextLCD library for an LCD20x4 type : the AV2040 of ANAG VISION (found @ Conrad). I have found the following problems and respective solutions that may help for a future release if it's OK for you :

1) the LCDType (enum in line 48 of TextLCD.h) is not used in the "Hello world" example of the Cookbook page : this example works only for the default LCD16x2 type !

2) when using the LCD20x4 type when calling the TextLCD class, a compilation error is : Identifier "LCD20x4" is undefined (E20).

3) consequently, I have modified the default LCDType = LCD20x4 in the TextLCD.h file only (nothing in the TextLCD.ccp file)

The code is : TextLCD lcd(p24, p26, p27, p28, p29, p30); /* rs,e,d0,d1,d2,d3,20 char's x 4 lines */

and the compilation is now OK and my LCD works very properly (I have written an interrupt driven frequencemeter with a fast partial LCD update which never failed).

I have not yet understood why the enum LCDType is "undefined". If this is fixed, I will use finally your library without change.

Thanks in advance !

Arwin Vosselman

# 23 Nov 2010

Dominique Bultez wrote:

I am using this TextLCD library for an LCD20x4 type : the AV2040 of ANAG VISION (found @ Conrad). I have found the following problems and respective solutions that may help for a future release if it's OK for you : 1) the LCDType (enum in line 48 of TextLCD.h) is not used in the "Hello world" example of the Cookbook page : this example works only for the default LCD16x2 type ! 2) when using the LCD20x4 type when calling the TextLCD class, a compilation error is : Identifier "LCD20x4" is undefined (E20).

You should use the identifier as follows:

TextLCD lcd(p15, p16, p17, p18, p19, p20, TextLCD::LCD20x4); rs, e, d0-d3

This works excellent for me.

Dominique Bultez

# 23 Nov 2010

Thanks a lot : Now this works excellent also for me with your original library !

john raines

# 05 Dec 2010

The writeByte routine can be speeded up by about a factor of 4 just by knowing that while commands take about 40usec, 'tickling the enable pin' can be done in 1/2 usec, so:

void TextLCD::writeByte(int value) {

wait(0.000040f); most instructions take 40us

_d = value >> 4;

wait_us(1);

_e = 0;

wait_us(1);

_e = 1;

_d = value >> 0;

wait_us(1);

_e = 0;

wait_us(1);

_e = 1; } works well and much faster.

A simple, but kind of kludgy, way to implement 40x4 support is to make some very simple changes to support a 40x2 display in the code around LCDtype and then to declare the upper two lines with something like:

TextLCD lcdupper(p10, p12, p15, p16, p17, p18, TextLCD::LCD20x4);

and the lower two lines with:

TextLCD lcdlower(p10, p13, p15, p16, p17, p18, TextLCD::LCD20x4); assuming enable2 is on pin 13.

john raines

# 05 Dec 2010

The 16x2B option you 'support' is, I think, a completely mythical device. If you know of an actual source for such a device, please let me know where I can purchase one. It would be something I would add support for in the Arduino LiquidCrystal library if it were real. see

http://web.alfredstate.edu/weimandn/lcd/lcd_addressing/lcd_addressing_index.html

Arwin Vosselman

# 05 Dec 2010

john raines wrote:

The 16x2B option you 'support' is, I think, a completely mythical device. If you know of an actual source for such a device, please let me know where I can purchase one.

AFAIK this is used for displays using the HD66712 or equivalent chip.

Juergen Hausmann

# 08 Dec 2010

Hello, did anybody try out the 20x4 LCD interfacing with SPI ? If so how does the identifier look like? Thank you Juergen Hausmann

Peter Drescher

# 08 Dec 2010

Hello, my 4x20 Display with a KS066 controller was not running with the TextLCD lib. I changed the delays and the init bytes - no change. I then add the RW signal to read from the display to poll the busy flag. It speed up the communication, but I only had access to the first and third line. Then i changed the E signal to be low between two commands. This is shown in the Samsung datasheet for the KS0066u. Bingo the display is working.

I have also add a writeCGRAM function to define user chars 0-7.

http://mbed.org/users/dreschpe/libraries/TextLCD/liznsz

Roger Nielson

# 28 Dec 2010

Having trouble compiling with "TextLCD.h" even with the above examples I get the following error message:

" Cannot open source input file "TextLCD.h": No such file or directory (E5)" in file "/main.cpp" "

Can someone point out what I'm missing. Scrpt as entered

#include "mbed.h"
#include "TextLCD.h"

TextLCD lcd(p15, p16, p17, p18, p19, p20, TextLCD::LCD8x2); // rs, e, d4-d7

int main() {
    lcd.printf("Hello!\n");
}

Roger Nielson

# 28 Dec 2010

Sorted thanks. Just needed to import it

Ismael Sanchez

# 04 Jan 2011

hi! I have a question, how can I to import this library?

khalil Ahmed

# 03 Jul 2011

guyz i have a question?

are the connection same for NHD‐0420E2Z‐FL‐YBW ???

Eric Elliott

# 07 Jul 2011

Hi Jim. Thanks for posting this. I tried to compile your program, but I couldn't get it to work. At first it said that TextLCD.h was missing. I copied that file from another library, and then it gave me error 289, "types of my input values do not match the types expected in the declaration of my function." I'm new to this stuff, so could you please explain what I need to do? Do I need to modify the header file, or is there something else that needs to be done. Thanks.

jim hamblen wrote:

Sorry about the mess in last comment - looked OK in edit window. Preview does not seem to work right in my browser

#include "mbed.h"
#include "TextLCD.h"

TextLCD lcd(p10, p12, p15, p16, p29, p30); // rs, e, d0-d3
Timer t;

int main() {
// Start timer
    t.start();
// Clear LCD Screen
    lcd.cls();
    wait(1);
// Print to LCD on first line
    lcd.printf("Hello LCD World!\n");
    while (1) {
// Move cursor to start of second display line
        lcd.locate(0,1);
// Print elapsed time from timer on LCD
        lcd.printf("%e sec", t.read());
        wait(.2);
    }
}

Arwin Vosselman

# 07 Jul 2011

khalil Ahmed wrote:

are the connection same for NHD‐0420E2Z‐FL‐YBW ???

See Spec: <http://www.newhavendisplay.com/specs/NHD-0420E2Z-FL-YBW.pdf>

jim hamblen

# 08 Jul 2011

Eric: try importing my entire demo project using this

» Import this program HelloLCD

Text LCD demo

My guess is that the library files were not imported correctly for your project setup (or perhaps have changed recently). Don't have an LCD with me to try it, but my version still compiles OK. You need to use "Import library" or sometimes "files" to get the library code - Note the gear logo with the library in the compiler left column when you expand the project files.

HM Yoong

# 10 Aug 2011

Hi:

I make use of TextLCD as follow:

#include <mbed.h>
#include <TextLCD.h>

TextLCD lcd(p10, p11, p12, p13, p14, p15, TextLCD::LCD20x2); // RS, EN, D4, D5, D6, D7

int main() {
  lcd.cls();
           // 123456789 123456
  lcd.printf("Hello World n\n");
  lcd.printf("Hello World 2\n");
  wait(3);
  lcd.cls(); // Clear screen, locate(c0, r0)
  lcd.printf("World 1 ");
  lcd.printf("and World 2");
}

When I tried it on a 20x4 LCD (without backlight), it works perfectly. However, if I tried it on a 20X2 LCD (with backlight), it does not work. (BTW, I did change the last parameters in TextLCD contructor). The diagram /media/uploads/yoonghm/lcd.jpg

For the LCD with backlight, the symptoms: a) The backlight LCD is working b) The contrast on the LCD is working as I can vary the resistance on the pot. c) No text appear.

It seems to be that there is a time issue.

Any idea? Thank.

Arwin Vosselman

# 10 Aug 2011

HM Yoong wrote:

For the LCD with backlight, the symptoms: a) The backlight LCD is working b) The contrast on the LCD is working as I can vary the resistance on the pot. c) No text appear.

Assume you mean, that you can vary the voltage (not only the resistance) with the pot.

Do black squares show up when you turn the pot?

If not, you might have a display, that needs a negative contrast voltage.

What type of display? What controller?

mbed signals are 3.3V. Most 5V displays will function though.

HM Yoong

# 10 Aug 2011

Hi Arwin:

I also varied the resistance for the backlight using a pot but I did not updated the diagram here. So I have pots for contrast and backlight.

I tried both of the LCDs on a PIC18F 3.3V development board, they were working properly too.

Black squares showed up when I turned the pot for the contrast. The controller is HD44780.

Lionel Bousfield

# 03 Sep 2011

With HD44780 or ST7066U controllers ... Pin5 Read\Write enable should be strapped to 0v (pin1) for Write enable ... or you'll just get black squares !

Gert van der Knokke

# 04 Sep 2011

Lionel Bousfield wrote:

With HD44780 or ST7066U controllers ... Pin5 Read\Write enable should be strapped to 0v (pin1) for Write enable ... or you'll just get black squares !

Warning!

With READ/nWRITE high you will have an IO conflict as the LCD is in 'output' mode (read) and your mbed is sending data also (output) this can damage the IO ports of the mbed and/or display.

Jo Pattyn

# 26 Sep 2011

To HM Yoong (post dd 10 Aug): try to disconnect D0..3 from ground. Just leave the pins not connected to anything. I had the same problem and this worked for me.

HO WING KIT

# 14 Oct 2011

For everyone want to show cursor on LCD Display, you may add followings statement on your files.

All Cursor On/Off procedure

#define CURSOR_ON  1
#define CURSOR_OFF 2

int TextLCD::cursor(int show) { 
int cur = _cursor;
    switch (show) {
    default : return cur;
              break;
    case CURSOR_ON  : writeCommand(0x0F);
                      wait_us(40);  
                      _cursor = show;
                      break;
    case CURSOR_OFF : writeCommand(0x0C);
                      wait_us(40);
                      _cursor = show;
                      break;
    }
    return cur;
}

Ivan Chan

# 16 Oct 2011

Can i write as following code?? TextLCD lcd(p5, p6, p7, p8, p9, p10); rs, e, d4-d7 Can i connect like this??

Nathan Lasseter

# 07 Dec 2011

I was getting artifacts and my LCD was not initialising correctly. After some investigation, it transpires that my 16x2 LCD (A Varitronix branded MDLS16265-SS-LV-LED04-16PIN) needs at least 16mS after an 0x01 (cls) according to the datasheet.

I edited the library, and now it works fine every time.

Eric Ebert

# 23 Dec 2011

I've tested with a Winstar WH1602-YGH-CT -> KS0066 (http://www.datasheetcatalog.org/datasheets2/30/303671_1.pdf) Display and it works :)!!! Connect VSS, K and RW of the Display and GND of the mbed. External 5V to VDD of the display -> (current for driving the back light is required). Use 1k fix and 15..25k adjustable between VDD and Vo. 80..100Ohms between VDD and A/Vee. p15->RS p16->E p17->DB4 p18->DB5 p19->DB6 p20->DB7 other DBs are floating in 4-Bit mode. Programm the sample and see a "Hello world!" with back light.

bhawna mulchandani

# 04 May 2012

I got 5.0V LCD. Did everything given above. But all I get is a line of underscores... something like this: _ _ _ _ _ _ _ _ _ _ _ _ _ _

Help please

bhawna mulchandani

# 08 May 2012

Mine work fine with 5.0V. Rest everything the same and pin 3 grounded.

Harris MacFarlane

# 03 Dec 2012

Thanks very much for code example. We're sending real time text across a room (as a start to a text messaging project) from a PC through xbees to an LCD screen using mbeds. Your code is superb. We had to change the int putc ( int c ) cmd in the header file to char to deliver the individual letters one at a time.

Regards.

Wim Huiskamp

# 31 Jan 2013

I fixed the address issues with different LCD types by updating the TextLCD lib.

There is now support for

LCD8x1, /< 8x1 LCD panel */
LCD8x2, /< 8x2 LCD panel */
LCD16x1, /< 16x1 LCD panel (Is in fact a 8x2 in different layout) */
LCD16x2, /< 16x2 LCD panel (default) */
LCD16x2B, /< 16x2 LCD panel alternate addressing */
LCD16x4, /< 16x4 LCD panel */
LCD20x2, /< 20x2 LCD panel */
LCD20x4, /< 20x4 LCD panel */
LCD24x2, /< 24x2 LCD panel */
LCD24x4, /< 24x4 LCD panel (for KS0078 controller)*/
LCD40x2 /< 40x2 LCD panel */
LCD40x4 /< 40x4 LCD panel (two controllers)*/

Also added is a new method getAddress(column,row) that will return the correct memoryaddress.

The new library also supports an I2C PCF8574 portexpander or a SPI expander as alternate serial interfaces.

An updated forked version of Text LCD is discussed here.

You can find the new lib here.

Some background discussions on the problem and examples of the new code are here.

jim hamblen

# 12 Feb 2013

At least a couple of the new 5V LCDs coming now from Sparkfun need a different contrast resistor. We had one that was all black squares and the characters were not quite visible (could only be detected at an extreme angle). Used a 2K resistor instead of the 1K and that fixed it.

Public Types
enum	LCDType { LCD16x2 , LCD16x2B , LCD20x2 , LCD20x4 }
	LCD panel format. More...
Public Member Functions
	TextLCD (PinName rs, PinName e, PinName d4, PinName d5, PinName d6, PinName d7, LCDType type=LCD16x2)
	Create a TextLCD interface.
int	putc (int c)
	Write a character to the LCD.
int	printf (const char *format,...)
	Write a formated string to the LCD.
void	locate (int column, int row)
	Locate to a screen column and row.
void	cls ()
	Clear the screen and locate to 0,0.

mbed

Table of Contents

Hello World!¶

» Import this program
TextLCD_HelloWorld - main.cpp

Warning

Text LCD Library¶

» Import this library into a program
TextLCD - TextLCD Class Reference

Public Types

Public Member Functions

Different LCD Panel Sizes¶

Enhanced Version of Text LCD¶

Reference¶

2 related questions:

48 comments:

Oliver Ryan wrote:

Jelmer Bruggink wrote:

Dominique Bultez wrote:

john raines wrote:

jim hamblen wrote:

khalil Ahmed wrote:

» Import this program HelloLCD

HM Yoong wrote:

Lionel Bousfield wrote:

Recent changes

mbed

Text LCD

Table of Contents

Hello World!¶

» Import this programTextLCD_HelloWorld - main.cpp

Warning

Text LCD Library¶

» Import this library into a programTextLCD - TextLCD Class Reference

Public Types

Public Member Functions

Different LCD Panel Sizes¶

Enhanced Version of Text LCD¶

Reference¶

2 related questions:

48 comments:

Oliver Ryan wrote:

Jelmer Bruggink wrote:

Dominique Bultez wrote:

john raines wrote:

jim hamblen wrote:

khalil Ahmed wrote:

» Import this programHelloLCD

HM Yoong wrote:

Lionel Bousfield wrote:

Recent changes

» Import this program
TextLCD_HelloWorld - main.cpp

» Import this library into a program
TextLCD - TextLCD Class Reference

» Import this program HelloLCD