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Topic: Character LCD is blank (Read 158 times) previous topic - next topic


May 09, 2015, 05:04 am Last Edit: May 09, 2015, 05:06 am by kundarsa
40x4 character LCD, Solomon LM1194SGL. I do not get any characters or boxes. I have used these LCD's on a breadboard before.

LCD 1-8 to Arduino 2-9 (i do not see anyone using pins 0&1 are they not comparable to 2+ ?
LCD 9 to Arduino 10.
LCD 15 to Arduino 11.
LCD 10 to Arduino 13.
LCD 11 to Arduino 12.
LCD 12 to Breadboard trim pot, when i fiddle with this the screen gets brighter green.
LCD 13 to Breadboard GND.
LCD 14 to Breadboard 10K resistor.
LCD 16 is NC when looking at traces.

Looking at the LCD pins 13&14 have larger traces. It has 2 HD44780A00 chips (hence the 2 enable pins). I am using this pinout http://www.microcontroller-project.com/uploads/2/2/1/5/22159166/1508528_orig.jpg. I still had this LCD partially hooked up to a breadboard so when i moved the project over to my new shiny Arduino for a first project i could tell the DB pins were the first 8 pins which matched this post http://forum.lcdinfo.com/viewtopic.php?f=6&t=1077. The LCD does have a back light but hose pins are on the other side of the board.

Not sure what i have done wrong.

Code: [Select]

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 13, 10, 2, 3, 4, 5, 6, 7, 8, 9);

void setup() {
  // put your setup code here, to run once:
  lcd.begin(40, 4);
  lcd.print("Hello World!");

void loop() {
  // put your main code here, to run repeatedly:
  lcd.setCursor(0, 1);


I am guessing i need library for a 4x40 display at this point. I did find the LiquidCrystal440 library but it needs to be updated for the current IDE. My smaller LCD's work fine, will tinker with those for now :\


May 09, 2015, 04:47 pm Last Edit: May 09, 2015, 05:21 pm by floresta
LiquidCrystal440 has been updated, almost 4 years ago.  Start here:--> http://code.google.com/p/liquidcrystal440/ and follow the Downloads link to get to the latest version.

Two of the lines on your 40x4 should work with the standard LiquidCrystal library using one of the Enable pins.  The other two lines should work if you use the other Enable pin.

LiquidCrystal lcd(12, 13, 10, 2, 3, 4, 5, 6, 7, 8, 9);
This works out as follows:

LCD               Your
Pin    Function   Arduino

01     D7         9
02     D6         8
03     D5         7
04     D4         6
05     D3         5
06     D2         4
07     D1         3
08     D0         2
09     Enable 1   10
10     R/W        13
11     RS         12
12     V5        
13     GND
14     +5 volts
15     Enable 2   11
16     NC

LCD 1-8 to Arduino 2-9
I think you may have the eight data lines exactly wrong.

You can run the full display if you use two instances of the standard LiquidCrystal library but LiquidCrystal1.0 (the updated LiquidCrystal440) is a better choice.



May 09, 2015, 04:59 pm Last Edit: May 09, 2015, 05:22 pm by floresta
LCD 12 to Breadboard trim pot, when i fiddle with this the screen gets brighter green.
That's not normal.  With just the power and contrast pins connected, pins 12, 13, and 14 in your case, you should have a blank screen at one end of the pot and two lines (maybe all four) of 'blocks' at the other.

Try this with one of your 'normal' LCDs to find out what I mean.  You should get a blank screen at one end, and half the character positions, appearing as solid blocks, at the other.  You might get all of the character positions showing as blocks with some LCDs.  In that case turn the pot back until you can just see half of them.


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