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Topic: newbie having problems with 4bit LCD (4x20) (Read 3057 times) previous topic - next topic


row #1 & #3 have all 20 char boxes illuminated
row #2 & #4 have all 20 blank

My setup
Arduino v0007
Display HD44780 20X4 Character LCD Display with BLUE backlight

i  followed
Library & example http://www.arduino.cc/playground/Code/LCD4BitLibrary
Wiring http://www.arduino.cc/playground/uploads/ScematicLcd/scematic_lcd.pdf

I tried
-w & w/o RW low
-USING_RW is true or false.
-checked wiring 3x
-LCD4Bit lcd = LCD4Bit(1); & LCD4Bit lcd = LCD4Bit(4); (also uncommented "2nd line")


Oct 01, 2009, 04:31 am Last Edit: Oct 01, 2009, 04:57 am by lep136 Reason: 1
SUGESTION!!! use a potentiometer from pin 3 to ground.  This is the contrast display.  It took me 5 hours to find out that you have to use a potentiometer to edit the contrast otherwise you will not see anyting on the lcd.  Just the backlit.   Also, I got to see bargled symbols sent to the lcd, but I have not been able to send actual messages to it..

let mek now if you have any success.  My email is monstertech5000@gmail.com

so far I downloaded the LCD4Bit library and added it to both \hardware\libraries\LCD4Bit

please help.


row #1 & #3 have all 20 char boxes illuminated
row #2 & #4 have all 20 blank

This is normal for a display that has power applied but has not been initialized properly.

so far I downloaded the LCD4Bit library ...

The original post is 2-1/2 years old and so is the library you mentioned.  Try using the latest version of the LiquidCrystal library (Arduino v0017) and see if things work out better.



I see... I used a potentiometer to edit the contrast and also grounded the RW pin.. I have not edited the library code to false.. i'm not sure if I have to do that.  but I see all kinds of symbols scrolling through the lcd.  

I think i might be send it incorrect  commands.

I have the following

LCD pin       Arduino pin
1                 ground
2                 5v
3                 potentionmeter to ground
4                 12
5                  ground
6                 3
11               7
12               8
13               9
14               10
15               14
16               ground

this worked for us.

the library we used was LCD4Bit 4X40  even though we have a 4X20 8-) 8-) 8-) 8-) 8-)


You need to have this on the POT:

  [||||]     [||||]    [||||]
   +5v      pin 3     Ground


but I see all kinds of symbols scrolling through the lcd

This means the contrast is OK so you can forget about that part and concentrate on the software.

If you have done any internet research on LCDs you should realize that getting these things to work has been a problem for many people for quite a while.  As a result it seems that as soon as someone gets one to work they post their code.  The problem is that many of these 'solutions' do not adhere to the manufacturers datasheet and therefore the fact that they work on one particular LCD does not mean that they will work on others.

The current version of LiquidCrystal is proven code that does follow the manufacturers datasheet, particularly when it comes to timing.  You will save yourself a lot of problems if you forget about the LCD4Bit library.


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