I2C LCD Display

I2C LCD Display

I bought an I2C display on ebay and by the description it seemed it just might work out of the box… But it didn't …

Here is a description of how I got it to work, so next time I do not have to invent the wheel again.

My display has a PCB on the back labled “YwRobot Arduino LCM1602 IIC V1” but it appears it is the same as the the one of sainsmart.com The only difference is the text on the back.

There were a few (simple) steps in getting the display to work, you just need to know what they are. The display is basically a HD44780 LCD display and an PCF8574 I2C-to-parrallel IC

PIC Library

The code on this page is for an Arduino (compatible) microcontroller, however there is a PIC microcontroller library available too.

I have never gotten around to working with a PIC, but I received an email from MDP wrote a library for the LCD display to be used on a PIC18F4550

He has been kind enough to share this with the world, and he send me his code. You can download everything here

MDP also wrote a more universal library for the PIC, one that is also compatible with the adapter labled “mjkdz”. You can download the files here

A demo

But first, here is a demo of the LCD display

The Hardware

The display works on an I2C interface. There is a board on the back that takes I2C signals and translates them in to a parallel signal. The display its self is originally a parallel display.

The I2C address is “hard wired” of the address: 0x27 This is something you can't see on the board, you must read it in the provided documentation.

On the back is also a potentiometer, this is for adjusting the contrast. If you never get to see any chars but you were expecting the display to show something, you might want to try to adjust this potentiometer.

The connection to an Arduino (clone) is very simple to;

GND to GND (0V)
VCC to +5Volt
SDA to analog port 4 (PC4 or pin 27)
SCL to analog port 5 (PC5 or pin 28)

The software

You need to remove the standard liquidcrystal library, rename the old folder to something else. You can read here how to replace a library.

Next you need to install the liquidcrystal library that works. I found mine here: fmalpartida/new-liquidcrystal And there is also lots more information on the library here

I used their examples and came up with this little demo:

i2c_display.ino

/*
    ** Example Arduino sketch for SainSmart I2C LCD2004 adapter for HD44780 LCD screens
 ** Readily found on eBay or http://www.sainsmart.com/
 ** The LCD2004 module appears to be identical to one marketed by YwRobot
 **
 ** Address pins 0,1 & 2 are all permanently tied high so the address is fixed at 0x27
 **
 ** Written for and tested with Arduino 1.0
 ** This example uses F Malpartida's NewLiquidCrystal library. Obtain from:
 ** https://bitbucket.org/fmalpartida/new-liquidcrystal
 **
 ** Edward Comer
 ** LICENSE: GNU General Public License, version 3 (GPL-3.0)
 */
#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>
 
#define I2C_ADDR    0x27  // 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
 
int n = 1;
 
LiquidCrystal_I2C       lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);
 
void setup()
{
  lcd.begin (20,4,LCD_5x8DOTS);
 
 
  lcd.setBacklightPin(BACKLIGHT_PIN,POSITIVE); // init the backlight
}
 
void loop()
{
  demoDisplay();
  demoDisplay2();
 
  lcd.setBacklight(LOW);        // Backlight off
  lcd.home ();                   // go home     
  lcd.print("ABCDEFGHIJKLMNOPQRST"); 
  lcd.setCursor ( 0, 1 );        // go to the next line
  lcd.print("UVWXYZ 0123456789   ");
  lcd.setCursor ( 0, 2 );        // go to the next line
  lcd.print("abcdefghijklmnopqrst");
  lcd.setCursor ( 0, 3 );        // go to the next line
  lcd.print("uvwxyz <>!?@#$%&*() ");
  lcd.setBacklight(HIGH);     // Backlight on
  //lcd.on(); // Switch fully on the LCD (backlight and LCD)
  delay(3000);
 
 
 
  //lcd.setCursor (2,3);        // go col 2 of line 3
  //lcd.print(n++,BIN);          // print the value of n
 
  for (int i = 0; i < 20; i++) {
    delay(300);
    lcd.scrollDisplayLeft();
  }
  delay(3000);
 
  for (int i = 0; i < 20; i++) {
    delay(300);
    lcd.scrollDisplayRight();
  }
  delay(3000);
 
  lcd.clear(); // clear display, set cursor position to zero
  lcd.autoscroll(); // This will 'right justify' text from the cursor
  lcd.print("autoscroll");
  delay(3000);
 
  lcd.clear(); // clear display, set cursor position to zero
  lcd.noAutoscroll(); // This will 'left justify' text from the cursor
  lcd.print("noAutoscroll");
  delay(3000);
 
  lcd.clear(); // clear display, set cursor position to zero
  // This is for text that flows Right to Left
  lcd.rightToLeft();
  lcd.print("rightToLeft");
  delay(3000);
 
  lcd.clear(); // clear display, set cursor position to zero
  lcd.leftToRight(); // This is for text that flows Left to Right
  lcd.print("leftToRight");
  delay(3000);
 
  lcd.clear(); // clear display, set cursor position to zero
  lcd.print("blink");
  lcd.blink(); // Turns on the blinking cursor
  delay(3000);
 
  lcd.clear(); // clear display, set cursor position to zero
  lcd.print("noBlink");                  
  lcd.noBlink(); // Turns off the blinking cursor
  delay(3000);
 
  lcd.clear(); // clear display, set cursor position to zero
  lcd.print("cursor"); 
  lcd.cursor(); // Turns the underline cursor on/off
  delay(3000);
 
  lcd.clear(); // clear display, set cursor position to zero
  lcd.print("noCursor"); 
  lcd.noCursor(); // Turns the underline cursor on/off
  delay(3000);
 
  //lcd.off(); // Switch fully off the LCD (backlight and LCD) 
 
}
 
void demoDisplay() 
{
  lcd.clear(); // clear display, set cursor position to zero
  lcd.setBacklight(HIGH);     // Backlight on
  lcd.setCursor (0,0); 
  lcd.print("Good afternoon,");
  lcd.setCursor (0,1);        // go col 0 of line 1
  lcd.print("gentlemen.");
  delay(1000);
  lcd.setCursor (0,2);        // go col 0 of line 2
  lcd.print("I am a HAL 9000 ");
  lcd.setCursor (0,3);        // go col 0 of line 3
  lcd.print("computer.");
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("I became operational");
  lcd.setCursor (0,1);
  lcd.print("at the H.A.L. plant ");
  lcd.setCursor (0,2);
  lcd.print("in Urbana, Illinois ");
  lcd.setCursor (0,3);
  lcd.print("on January 12 1992. ");
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("My instructor was   ");
  lcd.setCursor (0,1); 
  lcd.print("Mr. Langley, and he ");
  lcd.setCursor (0,2); 
  lcd.print("taught me to sing   ");
  lcd.setCursor (0,3); 
  lcd.print("a song.             ");  
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("If you'd like to    ");
  lcd.setCursor (0,1); 
  lcd.print("hear it I can sing  "); 
  lcd.setCursor (0,2); 
  lcd.print("it for you.         ");
  lcd.setCursor (0,3); 
  lcd.blink(); // Turns on the blinking cursor
  delay(4000);
  wipeLines();
  lcd.noBlink(); // Turns off the blinking cursor
}
 
void demoDisplay2() 
{
 
  /*
   Dave Bowman: Hello, HAL. Do you read me, HAL?
   HAL: Affirmative, Dave. I read you.
   Dave Bowman: Open the pod bay doors, HAL.
   HAL: I'm sorry, Dave. I'm afraid I can't do that.
   Dave Bowman: What's the problem?
   HAL: I think you know what the problem is just as well as I do.
   Dave Bowman: What are you talking about, HAL?
   HAL: This mission is too important for me to allow you to jeopardize it.
   Dave Bowman: I don't know what you're talking about, HAL.
   HAL: I know that you and Frank were planning to disconnect me, and I'm afraid that's something I cannot allow to happen.
   Dave Bowman: [feigning ignorance] Where the hell did you get that idea, HAL?
   HAL: Dave, although you took very thorough precautions in the pod against my hearing you, I could see your lips move.
   Dave Bowman: Alright, HAL. I'll go in through the emergency airlock.
   HAL: Without your space helmet, Dave? You're going to find that rather difficult.
   Dave Bowman: HAL, I won't argue with you anymore! Open the doors!
   HAL: Dave, this conversation can serve no purpose anymore. Goodbye. 
   */
 
  lcd.setCursor (0,0); 
  lcd.print("Hello, HAL.         ");
  lcd.setCursor (0,1);        // go col 0 of line 1
  lcd.print("Do you read me, HAL?");
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,2); 
  lcd.print("Affirmative, Dave. ");
  lcd.setCursor (0,3);        // go col 0 of line 1
  lcd.print("I read you.        ");
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("Open the pod bay   ");
  lcd.setCursor (0,1);        // go col 0 of line 1
  lcd.print("doors, HAL.        ");
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,1); 
  lcd.print("I'm sorry, Dave.   ");
  lcd.setCursor (0,2);
  lcd.print("I'm afraid I can't ");
  lcd.setCursor (0,3);
  lcd.print("do that.           ");
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("What's the problem? ");
  delay(4000);
  wipeLines();  
 
  lcd.setCursor (0,1);
  lcd.print("I think you know    ");
  lcd.setCursor (0,2);
  lcd.print("what the problem is ");
  lcd.setCursor (0,3);
  lcd.print("just as well as I do");
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("What are you talking");
  lcd.setCursor (0,1);
  lcd.print("about, HAL?         ");
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("This mission is too ");
  lcd.setCursor (0,1);   
  lcd.print("important for me to ");
  lcd.setCursor (0,2); 
  lcd.print("allow you to        ");
  lcd.setCursor (0,3); 
  lcd.print("jeopardize it.      ");
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("I don't know what   ");
  lcd.setCursor (0,1); 
  lcd.print("you're talking about");
  lcd.setCursor (0,2); 
  lcd.print(", HAL.");
  delay(4000);
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("I know that you and ");
  lcd.setCursor (0,1); 
  lcd.print("Frank were planning ");
  lcd.setCursor (0,2);
  lcd.print("to disconnect me,   ");
  delay(4000);
  lcd.setCursor (0,0); 
  lcd.print("and I'm afraid      ");
  lcd.setCursor (0,1); 
  lcd.print("that's something I  ");
  lcd.setCursor (0,2); 
  lcd.print("cannot allow to     ");
  lcd.setCursor (0,3); 
  lcd.print("happen.             ");
  delay(4000);  
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("Where the hell did  ");
  lcd.setCursor (0,1);
  lcd.print("you get that idea,  ");
  lcd.setCursor (0,2);
  lcd.print("HAL?");
  delay(4000);  
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("Dave, although you  ");
  lcd.setCursor (0,1);
  lcd.print("took very thorough  ");
  lcd.setCursor (0,2);
  lcd.print("precautions in the  ");
  lcd.setCursor (0,3);
  lcd.print("pod against my      ");
  delay(4000);  
  lcd.setCursor (0,0); 
  lcd.print("hearing you, I could");
  lcd.setCursor (0,1);
  lcd.print("see your lips move. ");
  lcd.setCursor (0,2);
  lcd.print("                    ");
  lcd.setCursor (0,3);
  lcd.print("                    ");
  delay(4000);  
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("Alright, HAL. I'll  ");
  lcd.setCursor (0,1);
  lcd.print("go in through the   ");
  lcd.setCursor (0,2);
  lcd.print("emergency airlock.  ");
  lcd.setCursor (0,3);
  lcd.print("                    ");
  delay(4000);  
  wipeLines();
 
 
  lcd.setCursor (0,0); 
  lcd.print("Without your space  ");
  lcd.setCursor (0,1);
  lcd.print("helmet, Dave? You're");
  lcd.setCursor (0,2);
  lcd.print("going to find that  ");
  lcd.setCursor (0,3);
  lcd.print("rather difficult.   ");
  delay(4000);  
  wipeLines();
 
  lcd.setCursor (0,0); 
  lcd.print("HAL, I won't argue  ");
  lcd.setCursor (0,1);
  lcd.print("with you anymore!   ");
  lcd.setCursor (0,2);
  lcd.print("Open the doors!     ");
  lcd.setCursor (0,3);
  lcd.print("                    ");
  delay(4000);  
  wipeLines();  
 
  lcd.setCursor (0,0); 
  lcd.print("Dave, this          ");
  lcd.setCursor (0,1);
  lcd.print("conversation can    ");
  lcd.setCursor (0,2);
  lcd.print("serve no purpose    ");
  lcd.setCursor (0,3);
  lcd.print("anymore. Goodbye.   ");
  delay(4000);  
  wipeLines(); 
 
}
void wipeLines() {
  for (int y = 0; y < 4; y++) {
    for (int x = 0; x < 20; x++) {
      lcd.setCursor (x,y);
      lcd.print(" ");
      delay(10);
    }
  }
}

Table of Contents

I2C LCD Display

PIC Library

A demo

The Hardware

The software