Two white rows on 20x4 I2C LCD display

Other Hardware Displays
1

Hi, I recently bought white & blue 20x4 I2C LCD display but after putting my code into arduino I found out that the lower two rows stay white no matter what I do. The upper two rows work just fine. I'm using LiquidCrystal_V1.2.1 library which should have no problems with 20x4 I2C displays. Even when I set the cursor on third row and wriite a word there, it still stays white. Ideas? I'm worried it can be hardware issue. My code:

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

LiquidCrystal_I2C lcd(0x27,2,1,0,4,5,6,7);
File root;
const int chipSelect = 4;

void setup()
{
  lcd.begin(20,4);
  lcd.setBacklightPin(3, POSITIVE);
  lcd.setBacklight(HIGH);
  Serial.begin(9600);

  Serial.print("Initializing SD card...");
  pinMode(SS, OUTPUT);

  if (!SD.begin(chipSelect)) {
    Serial.println("initialization failed!");
    lcd.setCursor(2,2);
    lcd.print("No card inserted");
    return;
  }
  else {lcd.setCursor(4,0);
        lcd.print("Card present");}
        
  Serial.println("initialization done.");
  

  root = SD.open("/");
  
  printDirectory(root, 0);
  
  Serial.println("done!");
}
2

Many concerns here.

First, drop the SD card stuff, write a version which just prints something on each of four lines.

Next, post a picture (preferably inline, not as an attachment) of the behaviour.

3

So I reduced my code to minimum:

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

LiquidCrystal_I2C lcd(0x27,2,1,0,4,5,6,7);
const int chipSelect = 4;

void setup()
{
  lcd.begin(20,4);
  lcd.setBacklightPin(3, POSITIVE);
  lcd.setBacklight(HIGH);
  Serial.begin(9600);
  lcd.setCursor(0,0);
  lcd.print("hello");
  lcd.setCursor(0,1); 
  lcd.print("world");
  lcd.setCursor(0,2); 
  lcd.print("here");  
  lcd.setCursor(0,3); 
  lcd.print("I am");
}

void loop()
{
}

But sadly, it didn't help. Here's the picture:

I think it's faulty display in fact I found similar problem to mine here:
http://forum.arduino.cc/index.php?topic=274974.0

4

I think it's faulty display ...

I think so too. Too bad AngryBaldMan (from the similar problem you linked to) never reported back to let us know if a new display fixed the problem.

Don

5


Yes, well it does look as if that could be the case as you appear to have all the correct numbers in your code.

except
Your descriptor includes pin numbers 0 and 1. These are the serial interface to the ATmega chip from the USB, and unless you have a really, really good reason to use these for something other than serial communication, you should not use these pins. I doubt however that this could be the cause of the problem as such. Unlikely.

Picture gone?

That's the trouble with using crap sites like "dropbox".

6

Paul__B:
Your descriptor includes pin numbers 0 and 1. These are the serial interface to the ATmega chip from the USB, and unless you have a really, really good reason to use these for something other than serial communication, you should not use these pins.

I used those pins on 16x2 display and everything worked fine. Now I tried to change the pins but still the same result.

7

Paul__B:
except
Your descriptor includes pin numbers 0 and 1. These are the serial interface to the ATmega chip from the USB, and unless you have a really, really good reason to use these for something other than serial communication, you should not use these pins. I doubt however that this could be the cause of the problem as such. Unlikely.

I think you have had a brain fart.
The pin numbers in the I2C constructor are the i/o pin numbers for the PCF8574 not the Arduino.

--- bill

8

bperrybap:
I think you have had a brain fart.
The pin numbers in the I2C constructor are the i/o pin numbers for the PCF8574 not the Arduino.

Quite right.

Getting too keen to find the answer to a vexed problem, confusing myself!

Please ignore my previous rant.

9

lower two rows stay white no matter what I do

Are you saying that when you power up the LCD , without any software running, ALL the rows display 5x7 characters?

10

Guuuys, strange things are happening. Watch:

I think there's no doubt now that it's faulty.

11

Your display is clearly broken.

Just buy a new module from Ebay. They are not expensive.

David.

12

I asked the seller to resend, so when I get another one I will report here hopefully with good news.

13

So, my new 20x4 display arrived today and I can report with good news, all is working well. :slight_smile: