Re: LCD screen only showing blocks!

hey everyone im pretty new to arduino's and such, so i apologize if i dont know all the lingo and things yet. Heres my problem. I bought a 16x2 lcd screen from spark fun its model is GDM1620k that pdf is its specs. I've gone through alot of help articles on this forum and others but have yet to get it to work. I've tried different tutorials online about getting it up and going and still every time it just displays blocks. I have it set up right now as shown on the ladyada.net site below. So my wiring and code are exactly as shown on the site. Still all i get is solid blocks on both rows and across all 16 columns. any help would be greatly appreciated i can paste code and show pictures here but i figure they are already on the site so unless u really want them i'll just leave them there.. Thanks again! -Chase http://www.ladyada.net/learn/lcd/charlcd.html http://www.sparkfun.com/datasheets/LCD/GDM1602K.pdf

If you wired it as the ladyada article suggests she of course uses code and wiring different from the built in example.

The wiring in the ladyada article is matched by this line
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

This link shows the syntax
http://arduino.cc/en/Reference/LiquidCrystalConstructor

/*
  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
 * 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 25 July 2009
 by David A. Mellis
 
 
 http://www.arduino.cc/en/Tutorial/LiquidCrystal
 */

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

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

void setup() {
  // set up the LCD's number of rows and columns: 
  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:
  lcd.print(millis()/1000);
}

i had changed that line in the code and it still just shows all solid blocks

Still all i get is solid blocks on both rows and across all 16 columns

Both rows????

Did you get the single row of blocks as shown about midway through the tutorial, just above the line that says "This means you've got the logic, backlight and contrast all worked out. Don't keep going unless you've got this figured out!"? (NOTE: Her display is upside down).

How about this step a little below the previous one: "As mentioned, we'll not be using the RW pin, so we can tie it go ground. That's pin 5 as shown bere:"?

So my wiring and code are exactly as shown on the site.

I've heard that before....

Post a cut and paste version of the code that you used along with a photo of the connections used with that code and the display resulting from the combination.

Don

going back and hooking up to the pot. step, back light comes on but no single row of blocks like the photo shows.
im sure you’ve heard it a million times lol i can rephrase that… to me it appears that everything is hooked up correctly… most likely something is wrong or else it would work. lol
whats a common problem with the solid blocks not showing up like in the photo

Pull out all the wires and start over. Then if it fails again post code and a photo of the wiring.

whats a common problem with the solid blocks not showing up like in the photo

bad potentiometer/potentiometer not adjusted/connected correctly. or it could be connected up and it's working fine but you haven't sent any data to it. Then you would just still have a blank screen.

Mowcius

or it coule be connected up and it's working fine but you haven't sent any data to it. Then you would just still have a blank screen.

If he's following the Lady Ada tutorial he hasn't connected the LCD to the Arduino yet.

Don

If he's following the Lady Ada tutorial he hasn't connected the LCD to the Arduino yet.

Ahh ok. I have not read that tutorial

when i connect it up to the step where she says "if u turn the pot. u can see the first row of blocks" i see nothing... there is a backlight on, if i start putting the Dpins in then it lights up all of the blocks. I desoldered everything and resoldered it and changed slots on and checked the continuity on the breadboard to make sure there wasn't a bad connection in there... and so far im back just back to where i should be seeing the blocks when i turn the pot ... and again nothing. I was going to see if it was just the type of LCD im using that wont show ne thing until it has Dpins attached or if im doing something wrong now i want to catch it before i go on.

http://www.mobog.com/p/yellowcouch/1ld44e http://www.mobog.com/p/yellowcouch/2nkh21 a couple photos of the circuit... sorry had to take them with my cell phone ... lol and sorry bout the long wires... basically i have gnd on the lcd going to gnd on arduino same with pin 16 then i have +5 going to +5 on arduino same with pin 15....then pin 3 is in the middle of the pot. then one side of pot goes to ground and the other side goes to +5 and thats it for right now... according to the tutorial i should be seeing the first row of blocks... but i turn the knob and nothing

yellowcouch,

You used the LCD UPSIDE DOWN!

What you thought as pin 1 is actually pin 16. The wiper or middle connection of your pot should connect to pin 3 but you got it on 14 because you thought 16 were 1. Yes, the backlight turns on, but that is because pin 1 and 16 are both ground, while pin 2 and 15 are both 5V. So as long as you use the LCD upside down, both the logic and backlight are powered (bad standard for novice). Just turn it around and it will work. Don’t feel embarassed. I did it once also. ;D

yellowcouch:

The pin numbers are shown on the datasheet that you linked to in your original post.

You should consider soldering a header (or some short wires) to the connections on your LCD module. Then you could plug the module into your solderless breadboard as was done in the tutorial.

Don

had it backwards... apparently .... on the back of hte LCD screen its silk screened and on pin 15 and 16 it says - and + so i just assumed that those were pins 1 and 2 ....thanks for the help sorry bout the noob mistake lol hopefully i can get the rest of the tutorial to work out. I appreciate the help! this is a good community = ]

this is a good community = ]

Indeed it is.

LCDs seem to be one of the most commonly asked about devices and it's normally always human error. I messed it up first time I connected my LCD up too. Granted it was a 40x4 with an 8x2 header and I got the data pins the wrong way round ::)

Mowcius

mowcius,

What would you suggest for a cable to connect the 8x2 header to a breadboard? I'm using a 40pin IDE harddrive ribbon cable, a bit too large.

One of these:

;):
Just search for 16 pin ribbon cable and they will come up.

Mine happened to already have one attached to it when I got it. :slight_smile:

Mowcius

I think i can just add to this post lol well.... i got the lcd working and everything then i put it into a project tested it with a key pad and it worked just fine... then i went for a final trouble shooting session turned it on and the lcd screen lit up but didn't display msgs... so i went through and did a little trouble shooting ... looking for loose connections or bad solder joints anyways so i just did the basic serial display program that comes in the examples part in the program and when i type all that it displays is ||||||?|||||| any ideas whats going on ? also i have the baud rates matching at 9600 thanks!

You appear to have appended a problem concerning a serial LCD implementation to an old thread concerning parallel LCDs.

Don

yes yes i have... do i need to make a new thread? I figured since it is dealing with the same lcd screen in question in the very first post i could tack it on the end... but if not i will gladly make a new post = ] sorry im pretty new to this stuff.