1

I've bought a cheap I2C LCD display (specs in the end of this question).

I can't make it print. I've tested with two displays of same model, so nothing is broken.

I am using the NewliquidCrystal 1.3.4 library, ie not the "normal" LiquidCrystal library. I'm trying with the I2C example called HelloWorld_i2c (link to example code). I've only changed the address from 0x37 to 0x27.

It compiles fine, but the result is only that the display flickers.

What is wrong and how do I fix it?

Super simple example flickers too

Well, this one gives just one blink.

#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27);  // Set the LCD I2C address
void setup()
{
  lcd.begin(16,2);               // initialize the lcd 
  lcd.home ();                   // go home
  lcd.print("Hello, ARDUINO ");  
}
void loop()
{
}

Pictures

In the light it shows that the writing to the display is randomly jumping around.

enter image description here

In the dark, it shows that the background light flickers:

enter image description here

Details about the LCD display

Text on the backside

YwRobot Arduino
QAPASS
LCM1602 IIC V1

Text on the chip

TLPCF85747
HA
T62281
A N 1
I L knM988223
  • First hit on google: arduino-info.wikispaces.com/LCD-Blue-I2C - have you followed all that first? – Majenko Feb 4 '16 at 14:01
  • This is probably an issue of wiring; include your schematic. – TisteAndii Feb 4 '16 at 14:09
  • @Majenko: in fact I did look at that example before posting. I thought that did not work either; though in a different way; it just did not show anything. In fact the Arduino-Info example did work! But the display contrast setting was bad, my room is very bright, and most important: I was looking at it at a bad angle; and therefore I could not see any text. So if the contrast would have been set right, I would have had luck with the Arduino-Info example. – Mads Skjern Feb 4 '16 at 14:30
  • Regarding the HelloWorld_I2C example; by using this constructor call it worked: LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); – Mads Skjern Feb 4 '16 at 14:31
  • 1
    Feel free to answer it yourself since it was you that worked out how to get it working. I merely showed you the path :) – Majenko Feb 4 '16 at 14:36
2

I was able to make the example run as intended, by using a different constructor call:

LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);

I am not able to tell you, what these parameters and values mean. However, the documentation for this constructor is shown below (source).

/*!
    @method     
    @abstract   Class constructor. 
    @discussion Initializes class variables and defines the I2C address of the
    LCD. The constructor does not initialize the LCD.

    @param      lcd_Addr[in] I2C address of the IO expansion module. For I2CLCDextraIO,
    the address can be configured using the on board jumpers.
    @param      En[in] LCD En (Enable) pin connected to the IO extender module
    @param      Rw[in] LCD Rw (Read/write) pin connected to the IO extender module
    @param      Rs[in] LCD Rs (Reset) pin connected to the IO extender module
    @param      d0[in] LCD data 0 pin map on IO extender module
    @param      d1[in] LCD data 1 pin map on IO extender module
    @param      d2[in] LCD data 2 pin map on IO extender module
    @param      d3[in] LCD data 3 pin map on IO extender module
    */
   LiquidCrystal_I2C( uint8_t lcd_Addr, uint8_t En, uint8_t Rw, uint8_t Rs, 
                     uint8_t d0, uint8_t d1, uint8_t d2, uint8_t d3 )
;
0

Try to pull the I2C sensor at the back of the LCD board, you can see that it is shorted to the SMD mounted on the back, just pull it a little so that it won't touch and short the conductors. This has happened to me, try it if this works.

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