next topic »

[on:]

This is a repost since I posted in the wrong section earlier but..

recently taken up the challenge of getting an LCD output working as I found a 14 pin LCD display with a Hitachi HD44780 driver. The down side was there was no data sheet with the screen so I've been using standards found on google.

So far,  when i fire it up I can only get 1 row out of the two to light up with solid squares. Does this mean the screen is faulty or have I miss connected one of the leads?
the second mystery comes when I use the liquid crystal tutorial, the squares are wiped off the screen and I am no longer able to see ANYTHING ( the print didnt work..)

any suggestions are much appreciated..

[Reply #1 on:]

So far,  when i fire it up I can only get 1 row out of the two to light up with solid squares. Does this mean the screen is faulty or have I miss connected one of the leads?

This means that the LCD controller is not properly initialized.  This is usually due to improper connections.  How did you deal with pin 5 (R/W) of the LCD?

the second mystery comes when I use the liquid crystal tutorial, the squares are wiped off the screen and I am no longer able to see ANYTHING

Try following the tutorial at http://www.ladyada.net/learn/lcd/charlcd.html.  Make sure you follow it step by step, and near the middle of the tutorial, before the data lines are connected to the Arduino, you will see a photo of your squares (the display is upside down at this point so it looks like the second row has the squares).

Please report back.  If things still aren't working then we need a photograph of your connections.

Don

[Reply #2 on:]

If you have an LCD with -14- pins I think this is the tutorial you need to look at:

http://www.ladyada.net/learn/lcd/lcdshield.html

I scrounged up a couple of no-name LCDs and that page did the trick even though I was not wiring mine to a shield. Also, beware. Watch how you connect to that LCD as the pinout shown is reverse from what you need.

(No, I did not chase my tail for an hour until that dawned on me. No I didn't!!  )

[Reply #3 on:]

If you have an LCD with -14- pins I think this is the tutorial you need to look at:

All of the HD44780 based LCD modules have a 14 pin interface.  Some have  a single row of 14 pins as shown in the link in reply #1 and some have two rows of 7 pins as shown in the link in reply #2.  Most of the newer LCD modules that incorporate a backlight put the connections for that backlight on two pins that are adjacent to the 14 pin LCD interface.  That does not change the LCD interface to a 16 pin interface. 

Watch how you connect to that LCD as the pinout shown is reverse from what you need.

Doesn't that depend on which side of the board you are looking at? 

Don

[Reply #4 on:]

Yeah, I recall one person had a display with reversed pin order, possibly because the pins are below the display instead of above. You can call it reverse but the pin numbers 1 and 14 (or 16) are printed on the board so if you look carefully, you can notice that.

The funny thing is, if you reverse all pins, with a lucky strike, your display "works" since you'll be powering logic, where you thought you were powering back light and vice versa, due to the "pin1=gnd , pin2=5V, pin 15=5V, pin16=gnd" symmetry. Just the trimpot has no effect on the display contrast, or worse, garbles message.