Lcd16x2

[Leda Billock]

HiEveryone. First of all, thank you for any help you can offer. I am stuck and unable to help my students with this problem. I am new to Arduino and the programming. I am trying to get the basic display sign showing and it only shows weird characters, they seem to be in the correct place for "hello, world!" but that is not what is it showing.

Demonstrates the use a 16x2 LCD display. The LiquidCrystal

library works with all LCD displays that are compatible with the

Hitachi HD44780 driver. There are many of them out there, and you

can usually tell them by the 16-pin interface.

I've never really tried to use the lcd 16x4 that way. You should try using it with I2C. It's cake work and only uses 4 wires. Tx,Rx,positive,negative. The programming is so easy with the i2c library commands.

Most of the displays come with the i2c module but you can get one for 99 cents and it solders to the back of the display.

Sorry, I know that's probably not what you were looking for but from experience with lcd16x2 or 20x4 it's the way to go.......especially if remote mounting the display

Can you point out which I2C library commands differ from the commands in the regular LCD library (other than the constructor)? I suppose you might be thinking about the backlight but that really has nothing to do with the LCD.

Yep, INTP is correct.....Bad soldering will cause untold types of issues, u can't short the data pins.

Sorry for going off topic. Just wanted to let em know there is a much simpler way to work with the 16x2 LCD.....and it's far less prone to wiring troubles. Though you would still need to solder the I2C module correctly on those same exact pins.

Rookie forum mistake, point taken.

JoeySC:

Yep, INTP is correct.....Bad soldering will cause untold types of issues, u can't short the data pins.

Sorry for going off topic. Just wanted to let em know there is a much simpler way to work with the 16x2 LCD.....and it's far less prone to wiring troubles.

While using an i2c backpack is less prone to wiring issues, it is not really less prone to issues.

Most of the libraries are hard coded for a particular mapping and if the mapping doesn't match the backpack h/w then it won't work.

Add to this issue is that there are several libraries out there with the same name.

Also, there is the issue getting the i2c address correct. Many users stumble on this.

Then there is the issue of pullup resistors. Some backpacks have them some don't.

The mega 2560 boards have i2c pullups on the Arduino board but the other Arduino boards do not.

While the devices often work with the internal AVR pullups, it is WAY out of spec so they can be problematic and cause strange issues when there are no additional pullups.

The ARM arduino processors do not have internal pullups on the signals and require external pullups so if the device doesn't include them, it won't work.

Then lastly there can be the issue of 5v vs 3v on boards like DUE that made the awful decision to not be 5v tolerant. This means that you either have to use a voltage level converter or try to cheat by running the LCD at 5v but the i2c bus at 3v (which usually should work).

I'm seeing the same problems - with a correctly soldered LCD, might I add - but with added connection problems.

First, the program shouldn't be causing this, it's the standard LCD program supplied with an Arduino Uno R3. But check the variable resistor on the right side of your picture. It's really crummy (yep, I got that one, too) and must be fully turned before the display shows anything.

Well, 2 years later, I doubt your advice will be of any use to the Original Poster here, but since you mention the 10k contrast potentiometer, the correct advice would be to ensure it is disconnected from the 5 V supply - connect that end of the potentiometer back to the wiper - and replace it with a 1k value. Correcting a persistent blunder in the design of these display modules will vastly improve adjustment of the contrast.

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