I purchased this LCD: http://www.seeedstudio.com/depot/lcd-82-characters-blue-back-light-p-120.html
I found out Vdd and Vss were incorrectly labeled the opposite, so I applied the wrong voltage to each. Now when I try to display text on the LCD, I get a series of dashes. That's it.
I've double checked the pin diagram many times, and I'm running the sample code they have on their site. Nothing is working.
Could it be dead? What am I missing?
Alligator:
"I get a series of dashes" and "Nothing is working" actually convey conflicting information. A series of dashes indicates that the device is working, it's just working incorrectly.
I recommend that you ignore the information about the 'incompatibility' of the LiquidCrystal library at the Seeedstudio site. Their information is out of date.
If you are not already using Arduino v0017 then you should switch. If you are already using that version then you will have to restore the LiquidCrystal library that Seeedstudio had you overwrite.
Connect just the power, ground, and contrast (pins 1, 2, and 3. You should get a blank screen with the pot at one end and real dark boxes on the top row with the pot at the other end. Adjust the pot until the dark boxes are just visible. If you can't see the boxes don't bother trying to load and run any code.
Use the 'Hello World' sketch that comes with v0017. You won't see the whole message on your little screen but the sketch should still work.
Make sure your connections agree with those declared in your sketch. Don't forget to deal with pin 5 (R/W). The sample code assumes it is grounded.
Report back with your results. If it still doesn't work then a photo of your connections and one of your display will help us help you.
Don
Alligator:
I just scrolled the Seeedstudio screen and see that they don't use a contrast pot.
So change my fourth paragraph to read:
Connect just the power, ground, and contrast (pins 1, 2, and 3) and the backlight (pins 15 and 16). You should get a blank screen with the pot at one end and real dark boxes on the top row with the pot at the other end. Adjust the pot until the dark boxes are just visible. If you can't see the boxes don't bother trying to load and run any code.
Don
Don,
Thanks for taking the time to help, I really appreciate this.
I unsoldered all of my connections except for power to the LED, Vss, Vdd, and Vo (pins 1, 2, and 3). I can only see one row of really clear dashes across the screen, and a very, very faint set of black boxes. The boxes seem to be missing portions that correspond to the row of bright white dashes on the opposite edge of the screen.
In short, it doesn't appear to work correctly as far as I can tell. By the way, I'm running v0017, and have reinstalled the old LiquidCrystal library they told me to replace.
Alligator:
This doesn't look very promising. If you can scrounge up a 5K or 10K pot I would suggest that you hook up the recommended voltage divider for the contrast and see if the display responds as I outlined in my first post. One end of the pot goes to 5v, the other end goes to ground, and the wiper goes to pin 3. Most likely the row of dots corresponding to the line you see is toast, but the rest of the display may work well enough for you to tinker while you order a new LCD.
Don
I had to order some other parts, so I ordered a new LCD. Hopefully this one should work.