1602A-4 with atmega 2560 r3

Like many on this discussion group, I bought an I2C LCD device for my Arduino only to find that the documentation is non-existent.

with the code on arduino.cc/playground/Main/I2cScanner i got that the i2c adress is 0x20.
I2C_ADDR = 0x20

my lcd is a 1602-4 ver 2.1 specs: http://www.ywhome.com.cn/en_pro_pic/LCD-1602A-4.jpg with 16x2

the expander is a : MCP23008

based on this topic: http://forum.arduino.cc/index.php/topic,128635.0.html i tried to use this code. but nothing will happen.

/*
** 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 permenantly 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)
**
** NOTE: TEsted on Arduino NANO whose I2C pins are A4==SDA, A5==SCL
*/
#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>

#define I2C_ADDR    0x20  // Define I2C Address where the PCF8574A is
#define BACKLIGHT_PIN     3
#define En_pin  6
#define Rw_pin  5
#define Rs_pin  4
#define D4_pin  11
#define D5_pin  12
#define D6_pin  13
#define D7_pin  14

// old code, also tried.
//#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 (16,2);
  
// Switch on the backlight
  lcd.setBacklightPin(BACKLIGHT_PIN,POSITIVE);
  lcd.setBacklight(HIGH);
  lcd.home ();                   // go home

  lcd.print("SainSmart I2C tester");  
  lcd.setCursor ( 0, 1 );        // go to the 2nd line
  lcd.print("F Malpartida library");
}

void loop()
{
  // Backlight on/off every 3 seconds
  lcd.setCursor (14,3);        // go col 14 of line 3
  lcd.print(n++,DEC);
  lcd.setBacklight(LOW);      // Backlight off
  delay(3000);
  lcd.setBacklight(HIGH);     // Backlight on
  delay(3000);
}

if i try the liquidtwi librarie and example code. the lcd is showing stuff, but not the characters. for my idea the only thing that works then is the backlight, and sending thing.

please help me out.

with the code:

// include the library code:
#include <Wire.h>
#include <LiquidTWI2.h>

// Connect via i2c, default address #0 (A0-A2 not jumpered)
LiquidTWI2 lcd(0);

void setup() {
  // set the LCD type
  lcd.setMCPType(LTI_TYPE_MCP23008); 
  // set up the LCD's number of rows and columns:
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.setBacklight(true);
}

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);
  lcd.print("hello, world!");

}

the result is:

  • backlight is on
  • you can see a sort of sinus wave instead of characters

I have also been working on getting my 16X2 I2C LCD to work.
I am happy to say, after several hours, I have it working.
My solutions:

  1. I am using a Leonardo board, and didn’t realize that A4 and A5 don’t work on that board (there are dedicated pins near AREF).
  2. bperrybap, explained to me that;

There are many different i2c to hd44780 lcd libraries out there.
They do not work the same.
They use different constructors, have different capabilities, and have different
ways of initializing using different initialization functions and parameters.
Most of them them use hard coded output pin mappings.
And that makes things even more complex since I2C boards
don’t all use the same pin mappings.

My recommendation is to use fm’s library:
https://bitbucket.org/fmalpartida/new-liquidcrystal/wiki/Home
It replaces the LiquidCrystal library that ships with the IDE.
Some sites repost this library but this is the location for the original source.

This library works very well and offers the same capabilities across several interfaces,
including 4 bit parallel, 2 wire shift register, 3 wire shift register, and I2C using a PCF8574.
It is also faster than the others.

I downloaded the library suggested.

My init working code is.

#include <Wire.h>
#include <FastIO.h>
#include <I2CIO.h>
#include <LCD.h>
#include <LiquidCrystal.h>
#include <LiquidCrystal_I2C.h>
#include <LiquidCrystal_SR.h>
#include <LiquidCrystal_SR2W.h>
#include <LiquidCrystal_SR3W.h>


#define I2C_ADDR    0x27
#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
LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin,BACKLIGHT_PIN,POSITIVE);

i noticed that already. on the at mega 2560 i am using digital ports 20(SDA) and 21(SCL) also already used that library. but still don;t get the right setup. so it is still not working

still tried wat you said.

with this code, nothing happend:

#include <Wire.h>
#include <FastIO.h>
#include <I2CIO.h>
#include <LCD.h>
#include <LiquidCrystal.h>
#include <LiquidCrystal_I2C.h>
#include <LiquidCrystal_SR.h>
#include <LiquidCrystal_SR2W.h>
#include <LiquidCrystal_SR3W.h>


#define I2C_ADDR    0x20
#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
LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin,BACKLIGHT_PIN,POSITIVE);

void setup()   /*----( SETUP: RUNS ONCE )----*/
{
  Serial.begin(9600);  // Used to type in characters

  lcd.begin(16,2);   // initialize the lcd for 16 chars 2 lines, turn on backlight

// ------- Quick 3 blinks of backlight  -------------
  for(int i = 0; i< 3; i++)
  {
    lcd.backlight();
    delay(250);
    lcd.noBacklight();
    delay(250);
  }
  lcd.backlight(); // finish with backlight on  

//-------- Write characters on the display ------------------
// NOTE: Cursor Position: (CHAR, LINE) start at 0  
  lcd.setCursor(0,0); //Start at character 4 on line 0
  lcd.print("Hello, world!");
  delay(1000);
  lcd.setCursor(0,1);
  lcd.print("HI!YourDuino.com");
  delay(8000);  

// Wait and then tell user they can start the Serial Monitor and type in characters to
// Display. (Set Serial Monitor option to "No Line Ending")
  lcd.clear();
  lcd.setCursor(0,0); //Start at character 0 on line 0
  lcd.print("Use Serial Mon");
  lcd.setCursor(0,1);
  lcd.print("Type to display");  


}/*--(end setup )---*/


void loop()   /*----( LOOP: RUNS CONSTANTLY )----*/
{
  {
    // when characters arrive over the serial port...
    if (Serial.available()) {
      // wait a bit for the entire message to arrive
      delay(100);
      // clear the screen
      lcd.clear();
      // read all the available characters
      while (Serial.available() > 0) {
        // display each character to the LCD
        lcd.write(Serial.read());
      }
    }
  }

}/* --(end main loop )-- */


/* ( THE END ) */

Good to know the address, now, how about all the pins. Why do you think they are:

define En_pin 6

define Rw_pin 5

define Rs_pin 4

define D4_pin 11

define D5_pin 12

define D6_pin 13

define D7_pin 14

Are you getting backlight? I noticed if I left off the back light and polarity, I did not get any back light, but if I used a flashlight, I could see it was changing characters. But, you said you do have backlight I think?

Some suggest, a pullup resistor on the two lines (data & clock). I had a 4k on both for a while, but when I got it working, I pulled the resistors, and saw no change. Your board may be different.

Do you have any other URL for that display?

the link: http://dx.com/p/meeeno-iic-lcd-1602-2-6-green-screen-lcd-module-shield-for-arduino-225969

based on the fact that the LIQUIDTWI librarie is allmost working. i guess that if i change the code in the header file below it should work. but i don;t get the right settings

#define MCP23008_ADDRESS 0x20

// registers
#define MCP23008_IODIR 0x00
#define MCP23008_IPOL 0x01
#define MCP23008_GPINTEN 0x02
#define MCP23008_DEFVAL 0x03
#define MCP23008_INTCON 0x04
#define MCP23008_IOCON 0x05
#define MCP23008_GPPU 0x06
#define MCP23008_INTF 0x07
#define MCP23008_INTCAP 0x08
#define MCP23008_GPIO 0x09
#define MCP23008_OLAT 0x0A

this code:

#include <Wire.h>
#include <LiquidTWI2.h>

LiquidTWI2 lcd(0);

void setup() {
  lcd.setMCPType(LTI_TYPE_MCP23008); 
  lcd.begin(16, 2);
  lcd.setBacklight(true);
  // Print a message to the LCD.
  lcd.print("hello, world!");
}

void loop()
{
 

}

result this:

Yea, I got mine from dx.com also, just a little different tho. http://dx.com/p/funduino-iic-i2c-1602-lcd-adapter-board-w-2-5-lcd-screen-black-green-red-173588

I found 2 reviews, that gave me some info to get started. If you think it is the pin definations, look at http://arduino-info.wikispaces.com/LCD-Blue-I2C. They have about 3 common pin configurations listed there, maybe one?

To be clear, the sketch compiles and uploads with no errors? The backlight is lit? You have your IDE set to the board you are using?

It is strange for that new code to do anything, since you don't even specify the I2C address. ? ?

in the new code i;m using the liquid twi librarie

where the standarts are:

#define MCP23008_ADDRESS 0x20

// registers
#define MCP23008_IODIR 0x00
#define MCP23008_IPOL 0x01
#define MCP23008_GPINTEN 0x02
#define MCP23008_DEFVAL 0x03
#define MCP23008_INTCON 0x04
#define MCP23008_IOCON 0x05
#define MCP23008_GPPU 0x06
#define MCP23008_INTF 0x07
#define MCP23008_INTCAP 0x08
#define MCP23008_GPIO 0x09
#define MCP23008_OLAT 0x0A

so there is allready my i2c adress defined.

an yeah all the code is compinling and uploading without any errors. if i use your librarie, the backlight isn;t on. my ide is set to the bord i;m using

he is keeping the screen of the old code. so he isn;t even clearing the screen. so he isn''t communicating at all.

Back stepping. If your scan got the address, then the clock and data pins must be hooked correctly.

At
they suggest several common pin settings for 3 different versions:
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); // Set the LCD I2C address
LiquidCrystal_I2C lcd(0x20, 4, 5, 6, 0, 1, 2, 3, 7, NEGATIVE); // Set the LCD I2C address
LiquidCrystal_I2C lcd(0x20, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); // Set the LCD I2C address
I can see there could be a lot of variations, but they seem to think these are some of the most common.
Try these three, and maybe?

This was really frustrating for me yesterday. I had to turn the computer off, and start again this morning.Often if we sleep on it, it gets more understandable in the morning.

i allready tried all the 3 of them. non is working

LiquidTWI2 lcd(0); You forgot the address of the I2C chip, I doubt it is 0.

// Connect via i2c, default address #0 (A0-A2 not jumpered) LiquidTWI2 lcd(0);

0 is the default address witch is in the .h file of the librarie set to 0x20. as i set before.

but i tried to make it 0x20 an now i got the same situation. the blacklight is on. but the text isn;t correct. and he is putting everyting on the first line. nothing on the seccond

Sounds to me like the pins arrangement on the physical device is not the same as what the library expects, so it sets the correct bits on the wrong pins.

thecoolest that''s what i thought myself aswel. but if i look in the .h it says:

#define MCP23008_ADDRESS 0x20

// registers
#define MCP23008_IODIR 0x00
#define MCP23008_IPOL 0x01
#define MCP23008_GPINTEN 0x02
#define MCP23008_DEFVAL 0x03
#define MCP23008_INTCON 0x04
#define MCP23008_IOCON 0x05
#define MCP23008_GPPU 0x06
#define MCP23008_INTF 0x07
#define MCP23008_INTCAP 0x08
#define MCP23008_GPIO 0x09
#define MCP23008_OLAT 0x0A

i thought maybe of the this registers is wrong. but there not written in the normal way as in: "en, rw, rs, d1, d2, ...."" i don;t know witch i should change to get it right.

but this library is written for the: Adafruit I2C Backpack and mine is a meeeno IIC LCD v1.0 i searched all over the internet but i heared nobody about this i2c module. only where to buy it from, not how to make it work.

These are the registers of the MCP chip, not the pins going to the LCD. You need to get the datasheet for this chip (here) Then check with a multimeter which GPIO pin on the MCP goes to which pin on the LCD.

Then you change this code to suit the implementation of your I2C PCB:

#define I2C_ADDR    0x27
#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
LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin,BACKLIGHT_PIN,POSITIVE);

Have you tried putting pullup resistors on those two lines? I did, and then took mine off, but your board may require then. ?

Next suggestion: If you can't get this display to sync, tell DX.com you want them to send you another board that will work (the one I got). As of yet, there have been no reviews posted for that board. It is likely, no one has been able to get it to work. DX has been pretty reasonable with me about doa items.

is this enough? if i;m right the other gpio pins aren’'t connected.
someone got an idea witch implementation i need now?