20x4 LCD2004 I2C LCD Showing 2 solid lines

[jister13]

I just bought this lcd and when I hook it up it immediately displays two solid lines, and stays like that no matter what my program tells it to do.

Here is my code (default example):

Code: [Select]

#include <Wire.h>
#include <LiquidCrystal_I2C.h>



#define BACKLIGHT_PIN     13

LiquidCrystal_I2C lcd(0x38);  // Set the LCD I2C address

//LiquidCrystal_I2C lcd(0x38, BACKLIGHT_PIN, POSITIVE);  // Set the LCD I2C address


// Creat a set of new characters
const uint8_t charBitmap[][8] = {
   { 0xc, 0x12, 0x12, 0xc, 0, 0, 0, 0 },
   { 0x6, 0x9, 0x9, 0x6, 0, 0, 0, 0 },
   { 0x0, 0x6, 0x9, 0x9, 0x6, 0, 0, 0x0 },
   { 0x0, 0xc, 0x12, 0x12, 0xc, 0, 0, 0x0 },
   { 0x0, 0x0, 0xc, 0x12, 0x12, 0xc, 0, 0x0 },
   { 0x0, 0x0, 0x6, 0x9, 0x9, 0x6, 0, 0x0 },
   { 0x0, 0x0, 0x0, 0x6, 0x9, 0x9, 0x6, 0x0 },
   { 0x0, 0x0, 0x0, 0xc, 0x12, 0x12, 0xc, 0x0 }
   
};

void setup()
{
   int charBitmapSize = (sizeof(charBitmap ) / sizeof (charBitmap[0]));

  // Switch on the backlight
  pinMode ( BACKLIGHT_PIN, OUTPUT );
  digitalWrite ( BACKLIGHT_PIN, HIGH );
 
  lcd.begin(16,2);               // initialize the lcd

   for ( int i = 0; i < charBitmapSize; i++ )
   {
      lcd.createChar ( i, (uint8_t *)charBitmap[i] );
   }

  lcd.home ();                   // go home
  lcd.print("Hello, ARDUINO "); 
  lcd.setCursor ( 0, 1 );        // go to the next line
  lcd.print (" FORUM - fm   ");
  delay ( 1000 );
}

void loop()
{
   lcd.home ();
   // Do a little animation by writing to the same location
   for ( int i = 0; i < 2; i++ )
   {
      for ( int j = 0; j < 16; j++ )
      {
         lcd.print (char(random(7)));
      }
      lcd.setCursor ( 0, 1 );
   }
   delay (200);
}

Here is an image of my setup:

[groundfungus]

Are you sure of the address?  Find and use the !2C scanner program to make sure of the address.  Here is code for my LCD that works.

Code: [Select]

#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>

#define I2C_ADDR    0x3f  // Define I2C Address where the PCF8574A is
#define BACKLIGHT_PIN     3
#define En_pin  2
#define Rw_pin  1
#define Rs_pin  0
#define D4_pin  4
#define D5_pin  5
#define D6_pin  6
#define D7_pin  7
LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);

Your lcd.begin is for a 16 char X 2 line display.

[Nick Gammon]

An I2C scanner on this page:

http://www.gammon.com.au/i2c

[enhzflep]

Seriously curious as to why Mr Gammon didn't mention this line of code... He, of all people should have picked this up in an instant.

Disclaimer: I've only a 1602, so can't test the code.


You question topic says you're using a 20x4 Lcd, right?
Well then, it seems rather odd that you would try to initialize it with the settings for a 1602, as you do in this line:

Code: [Select]

  lcd.begin(16,2);               // initialize the lcd

I'd be surprised if (as groundfungus alludes to) that wasn't supposed to be

Code: [Select]

  lcd.begin(20,4);               // initialize the lcd

[Nick Gammon]

Seriously curious as to why Mr Gammon didn't mention this line of code... He, of all people should have picked this up in an instant.

Well, I do tend to skim once I identify a problem area. However, well spotted.

[groundfungus]

Reply #1 after the code?

[Nick Gammon]

Yes, I was responding to that.

[123Splat]

Back to the poster's issue:  Contrast setting?  The 16,2 setting works on 20,4 displays, just only lights up rows 1 & 3, instead of 1&2, or 1,2,3&4....
"solid lines" sounds like he's only getting solid character blocks, with all bits at the same contrast level (whether on or off).

[Cactusface]

Hi,
       Yes I've had the contrast problems. long ago when I was new to LCD's as 123 says it impossible to know what DOTS are on or off.
I am new to the Arduino and C so am struggling myself. I too want to try the i2c way with LCD's!  Just seen this on ebay and it looks like the answer: http://www.ebay.co.uk/itm/181193639379?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2648

Earlier this year I was playing with PIcaxe's and a not very good basic, still have a long way to go, but if you don't try you never know!  I don't see that defining the LCD as a 16x2 when it's a 20x4 would cause any problems! other then the text not being in the right place? Whereever that might be!!

Regards
Mel.