Trouble with 20x4 I2C display

kchau · October 2, 2014, 5:31am

Hi there,

I’m having trouble with an LCD display - It just shows 2 bars on lines 1 and 3. This is the code that I’m using:

gist.github.com

https://gist.github.com/kevinchau/c7ca0fa705dd0659f5ee

LiquidCrystal_I2C.cpp

// LiquidCrystal_I2C V2.0
 
// When the display powers up, it is configured as follows:
//
// 1. Display clear
// 2. Function set:
//    DL = 1; 8-bit interface data
//    N = 0; 1-line display
//    F = 0; 5x8 dot character font
// 3. Display on/off control:

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LiquidCrystal_I2C.h

#define ARDUINO_H
 
#ifndef LiquidCrystal_I2C_h
#define LiquidCrystal_I2C_h
 
#define LCD_CLEARDISPLAY 0x01
#define LCD_RETURNHOME 0x02
#define LCD_ENTRYMODESET 0x04
#define LCD_DISPLAYCONTROL 0x08
#define LCD_CURSORSHIFT 0x10

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main.ino

#include "application.h"
#include "LiquidCrystal_I2C.h"
 
LiquidCrystal_I2C   *lcd;
 
void setup()
{
    lcd = new LiquidCrystal_I2C(0x27, 20, 4);  // set the LCD address to 0x20 for a 16x2 //SparkCore bug, address is actually 27 but shifted (0x27*2)
    lcd->init();                      // initialize the lcd
    lcd->backlight();

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I have the display wired up with 4.7k Ohm pull-up resistors, on D0 and D1 - I’ve tried switching D0 and D1, nothing seems to be working.

Also tried the contrast adjustment.

No dice.

Any ideas?

maxint · October 2, 2014, 1:33pm

Last time I had similar problems with an LCD-display, it turned out that it didn’t get enough power. The voltage supplied was lower than what was required. I suggest you to verify the specs of the display. Second suggestion: test the display using an arduino or compatible clone using a different library. It could be the used code has bugs or incompatibilities…

kchau · October 2, 2014, 6:19pm

I’m using a 5V power supply board that plugs into the breadboard, It supplies 1A. I tried running the Spark from USB and the display from the power supply, still no dice.

Unfortunately I don’t have an Arduino to play with yet.

Could it be something in the code? Can someone run this on their setup and verify if it works?

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Trouble with 20x4 I2C display

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