does the LiquidCrystal() auto init 4 or 8bit LCD?

Using Arduino Programming Questions
1

Normally the hd44780 needs to be told if it is running 4 or 8bit mode.

Is this Initialization included when calling "LiquidCrystal()" ? Meaning if you have defined 4 wire it init for 4 bit and if you define 8 wires it init for 8bit?

If I look in the program "hello world" there are not Initialization for the 4bit LCD used.

I have a funny problem on an old 44780 + extension chip 44xx, 2x16 , the first 8 segments of line 1 and 2 works , but the last 8 sigments of line 1 and 2 are dark . I don't know if this is because of a wrong init or a burn LCD chip.

2

When you create your LCD object with 4 data pins, you are telling the library you want 4 wire.

3

When I use a compatible LCD in 4-bit mode, and pass in 4 address lines to the constructor, it works in 4 bit mode.

If you need to know more, how about reading the source? It's open source! On my machine, the source code ends up in arduino-0022\libraries\LiquidCrystal\LiquidCrystal.cpp

Inside LiquidCrystal::begin() you will find this:

  //put the LCD into 4 bit or 8 bit mode
  if (! (_displayfunction & LCD_8BITMODE)) {
    // this is according to the hitachi HD44780 datasheet
    // figure 24, pg 46

    // we start in 8bit mode, try to set 4 bit mode
    write4bits(0x03);
    delayMicroseconds(4500); // wait min 4.1ms

    // second try
    write4bits(0x03);
    delayMicroseconds(4500); // wait min 4.1ms
    
    // third go!
    write4bits(0x03); 
    delayMicroseconds(150);

    // finally, set to 4-bit interface
    write4bits(0x02); 
  } else {
    // this is according to the hitachi HD44780 datasheet
    // page 45 figure 23

    // Send function set command sequence
    command(LCD_FUNCTIONSET | _displayfunction);
    delayMicroseconds(4500);  // wait more than 4.1ms

    // second try
    command(LCD_FUNCTIONSET | _displayfunction);
    delayMicroseconds(150);

    // third go
    command(LCD_FUNCTIONSET | _displayfunction);
  }

So, yes, the library initializes the display into the right mode.

4

:wink: Yah, source is good , very good -

I did read the LCD lib.ref. but got lazy, thats why I wrote my post here . So OK it start out in 8bit and if that don't work switch to 4 . ( And if the display show dark dots , it is the display that is defective) .

I found a 4x20 and connected instead of the funny 2x16 , the 4x20 work perfectly in 4bit/wire mode.

Thanks.