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[on:]

Hi,

I have LCD1602 shield paired with mega2560 (Link to the setup). I am trying to print Hello World on the display. But for some reason it is not working.
My code compiles fine in Atmel studio 6 and uploads on the board, but nothing gets printed. There are just 16 blocks being displayed in the first row. Here is the code.

Code:

#define LCD_RS  8
#define LCD_EN  9
#define LCD_D4  4
#define LCD_D5  5
#define LCD_D6  6
#define LCD_D7  7


// initialize LCD object
LiquidCrystal lcd(LCD_RS, LCD_EN, LCD_D4, LCD_D5, LCD_D6, LCD_D7);

void setup() {
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.print("hello, world!");
}

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);
// print the number of seconds since reset:
lcd.print(millis()/1000);
}

I tried several combinations of pins that I thought were logically correct. But none of them worked.

Thanks for your help.

[Reply #1 on:]

I just looked at the bottom of the LCD. It seems like "E" is not connected to any pin. So when I mount the shield on the board, pin 9 on the board that goes to the shield does not connect to "E". Am I missing something here? Or is it that my shield has a manufacturing defect?

Thanks

[Reply #2 on:]

I just looked at the bottom of the LCD. Am I missing something here?

Very likely, try the top of the board, and you may find it.

Your code does not include the liquid crystal library, and I imagine that would be essential, no matter what you use to write it. I submit you would be better off using the standard Arduino IDE - if only because I'm pretty sure it would refuse to compile with a missing library.

Further, there are differences in the pin arrangements among various 16x2 shields. While your pin code is the same as mine, I believe it might be unusual. You should check the data sheet, if you have one.

[Reply #3 on:]

My code includes LiquidCrystal library. As I mentioned in my OP that I am able to successfully compile and link the code. It also uploads to the board.

I also tried using standard Arduino IDE, but it did not work. Ohh may be I did not try with the correct pin numbering when I compiled in Arduino IDE. I will try that and report my findings.

Will also look at the top of the board and see if there is any connection to the "E" pin.

Thanks.

[Reply #4 on:]

Hi,

I have LCD1602 shield paired with mega2560 (Link to the setup). I am trying to print Hello World on the display. But for some reason it is not working.
My code compiles fine in Atmel studio 6 and uploads on the board, but nothing gets printed. There are just 16 blocks being displayed in the first row. Here is the code.

Code:

#define LCD_RS  8
#define LCD_EN  9
#define LCD_D4  4
#define LCD_D5  5
#define LCD_D6  6
#define LCD_D7  7


// initialize LCD object
LiquidCrystal lcd(LCD_RS, LCD_EN, LCD_D4, LCD_D5, LCD_D6, LCD_D7);

void setup() {
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.print("hello, world!");
}

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);
// print the number of seconds since reset:
lcd.print(millis()/1000);
}

I tried several combinations of pins that I thought were logically correct. But none of them worked.

Thanks for your help.

At a bare minimum, an HD44780 compatible LCD needs:

RS - register select
RW - tied to ground
EN - enable (also called "E").
D4 thru D7 - highest 4 bits of the data bus

The Arduino LiquidCrystal library will work if you don't connect RW to a pin, but then you have to manually ground the RW pin (to lock the LCD in "write" mode).

[Reply #5 on:]

I haven't worked with this module, but if I was you I would abandon this LCD module and replace it with the I2C version which only needs two wires connected and doesn't waste I/O's (actually 4 wires including +5v and ground).

http://www.dfrobot.com/wiki/index.php?title=I2C/TWI_LCD1602_Module_%28SKU:_DFR0063%29

[Reply #6 on:]

I just looked at the bottom of the LCD. It seems like "E" is not connected to any pin. So when I mount the shield on the board, pin 9 on the board that goes to the shield does not connect to "E". Am I missing something here? Or is it that my shield has a manufacturing defect?

Thanks

Can you provide a couple pictures?

[Reply #7 on:]

Hello folks,

Finally success!! Just came home from work and tried uploading the code through Arduino ide with the following pins ( lcd(8, 9, 4, 5, 6, 7)) and it worked!! These were the same pin numbers that I was using when I tried uploading through Atmel Studio 6. So I am like what?? Why is it working when I upload using Arduino ide and why din't it work last night when I tried the same code through AS6.
Then I said ok, let me try uploading the same code using AS6, and voila! It worked.... So, now I am totally confused as to why it dint work last night and why is it working today....
1 possible explanation (which you guys can correct me if I am wrong) is that there seemed to be a very thin soldering metal on the route that connects the pin from my board to the "E" slot on the top side of the lcd board. I just removed it using my mailbox key. Is it possible that it was shorting something? I should have tried uploading the code before removing that soldering piece and that would have answered my question....But well....

Anyways.. I am happy that its working now, so I can continue with my project.
Thanks for your help!!

[Reply #8 on:]

Is it possible that it was shorting something?

Too bad you didn't take a good picture first. Yes, it could have been shorting something.

[Reply #9 on:]

// LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
// The pins above gave me solid blocks.
// The pins below gave me the correct display
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);
// and the reset button starts the count over.
2 and 3 appear to be interrupt 0 and interrupt 1
11 and 12 are MOS1 and MIS0
4, 5, 6, 7, 8, 9 don't have anything but 'digital PWM'

Maybe someone can explain the problem, but thanks for the correct pin out.
Anthony

[Reply #10 on:]

2 and 3 appear to be interrupt 0 and interrupt 1

They are, but, unless you are attaching something to them that can generate an interrupt AND registering a handler, using the pins is no problem.

11 and 12 are MOS1 and MIS0

Correct on a UNO or other 328 based board, but not on a Mega, and only if you use SPI.

The order of the pins that didn't work and the the order of the pins that do work is not the same. I wonder if that has anything to do with the failure to print with the first set of pins.