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Topic: 1602A lcd (Read 11366 times) previous topic - next topic


Hello,  I am trying to print to an lcd model 1602A.  The data sheet can be found here: http://www.longtech-display.com/produts/LCD%20MODULES/longtech%20pdf/LCM1602A.pdfBefore posting I tried as hard as I could to find a solution by running many tutorials..adafruit, google,  arduino learning system and have come up with the same reult which is random characters on the screen.  I was using my code, then I switched to the example code "hello world" in the arduino IDE to be sure it wasn't me.  I have removed the jumpers and installed them many times due to everyones tutorial posting...no no hook it up like this.  I bought the lcd from amazon (no documentation other than the page I bought it from linking the data sheet).  The back says QC1602A  V2.0.  Any one have any ideas.  Heres the code and pics.
Code: [Select]
 LiquidCrystal Library - Hello World

Demonstrates the use a 16x2 LCD display.  The LiquidCrystal
library works with all LCD displays that are compatible with the
Hitachi HD44780 driver. There are many of them out there, and you
can usually tell them by the 16-pin interface.

This sketch prints "Hello World!" to the LCD
and shows the time.

 The circuit:
* LCD RS pin to digital pin 12
* LCD Enable pin to digital pin 11
* LCD D4 pin to digital pin 5
* LCD D5 pin to digital pin 4
* LCD D6 pin to digital pin 3
* LCD D7 pin to digital pin 2
* LCD R/W pin to ground
* 10K resistor:
* ends to +5V and ground
* wiper to LCD VO pin (pin 3)

Library originally added 18 Apr 2008
by David A. Mellis
library modified 5 Jul 2009
by Limor Fried (http://www.ladyada.net)
example added 9 Jul 2009
by Tom Igoe
modified 22 Nov 2010
by Tom Igoe

This example code is in the public domain.


// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12,11,5,4,3,2);

void setup() {
 // set up the LCD's number of columns and rows:
 lcd.begin(16, 2);
 // Print a message to the LCD.
 lcd.print("hello, world!");

void loop() {
 // set the cursor to column 0, line 1
 // (note: line 1 is the second row, since counting begins with 0):
 lcd.setCursor(0, 1);
 // print the number of seconds since reset:

Thank you for your time.


May 06, 2013, 02:59 am Last Edit: May 06, 2013, 03:02 am by gearz Reason: 1
As the picture below shows I am powering the assemby with my own powersupply on the breadboard.  Therefore I did not hook up the arduino power and groud to power it.  I still have not hook up power for I have my own.  But connecting the arduino ground the bread board ground works.  *makes me wonder...  arduino's not grounded in usb?...*  Theres an engineering explanation for this...im off to find it.


But connecting the arduino ground the bread board ground works.

The signals from your Arduino to your LCD module need a return path back to the Arduino and that path is provided by the 'GND' pin.  The same GND pin is used for all of the signals and also for the DC power if you use the Arduino to power the LCD.



I understand.  Thank you for your response and time.

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