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Topic: [Help] How to know if text lcd still working ?? (Read 634 times) previous topic - next topic


I dont know if my text lcd still working. How do I test it. Will it power on and show something if I connect only VCC and GND pin. Sorry for my bad English. Thanks !


depending on the type it can have some demo/startup text. (probably not) .

There is often a separate pin for the backlight that can easily be tested by applying VCC.

For the rest connect it to an Arduino with example sketch of the LCD library seems to be the simplest way.
- http://arduino.cc/en/Tutorial/LiquidCrystal -

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)


I would suggest you follow my generic troubleshooting technique.

Here is my generic step by step approach that should work:

(1) If the module has a backlight then get it working properly.  This involves only pins 15 and 16 on most LCD modules.  Make sure to use a current limiting resistor if there is none on the LCD module.

(2) Get the power and contrast working properly.  This involves only pins 1, 2, and 3 on most LCD modules.  You should be able to just barely see blocks on one row of a two row display and on two rows of a four row display. 

NOTE:  The Arduino has not been used yet, except as a possible source for the power needed for the first two steps.  Do not try to go any further until this is working.  If you don't see the blocks then no amount of program code will help.

(3) Connect the LCD R/W pin (pin 5) to GND.

(4) Connect the six control and data wires between your LCD module and your Arduino.

(5) Upload your sketch and it should work.


If you have a 16x1 display and there are blocks only on the left half of the row in step 2 then use lcd.begin(8, 2); in your sketch.

If you still don't get a display then make sure that your wiring matches the numbers in the descriptor (or vice versa).

Code: [Select]
//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);      // put your pin numbers here

If you get a display but it is garbled or has some other problems then try again with a 'static' sketch, one that displays a simple message on the top row of the display and then stops.  All of your code should be in setup() and loop() should be empty between the brackets.

Code: [Select]

#include <LiquidCrystal.h>

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);      // put your pin numbers here

void setup()
  lcd.begin(16, 2);                          // put your LCD parameters here
  lcd.print("hello, world!");
  lcd.print("it works!");

void loop()

If you are still having problems then we need to see a photograph of your setup that clearly and unambiguously shows all of the connections between your Arduino and your LCD module.  We also need a copy/paste version of the code that you are actually using, not a link to the code that you think you are using.


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