LCD Problem

[booski]

This is more of a hardware question than code/software question so you may ignore some of the facts below.

I've got a little HD44780 LCD here which I MAY in a tiresome stupor have accidently applied power in reverse.

Now, im using this with a normal PIC and proton basic compiler and the built in HD44780 protocols so I know the code is spot on. Thing is, the display turns on and after initialising the screen, I get 2 lines of squares but if I try to write to the screen I get nothing, no response.

My question is, is the LCD fried? which is why it isn't responding or shall I try with a different pic combination?

 

[nick12ab]

Have you tried adjusting the contrast? The fact that you can initialize it suggests that it might still be alive.

 

[hippy]

Thing is, the display turns on and after initialising the screen, I get 2 lines of squares

What does it do when you just apply power and contrast, no data, E, R/W connections at all ?

If a 2-line display with contrast one way you'll see nothing, with it the other way you usually see blobs on the top line only. On a 4-line blobs often on first and third line only.

A better test than trying any number of PIC/PICAXE is to try another LCD.

For people playing with parallel LCD's the AXE132 would have good use as a diagnostic tool. It can print up a welcome message and then identify what addresses each line is at.

 

[booski]

Have you tried adjusting the contrast? The fact that you can initialize it suggests that it might still be alive.

Yes, I have adjusted the contrast and have it set to max.

What does it do when you just apply power and contrast, no data, E, R/W connections at all ?

It only shows 'blobs' as you call them on the top line only. I should have mentioned that it's a 1602 display in 4 bit mode.
After the PIC initialises it shows 2 lines of blobs.

Must mean there is some sort of communication going on there then?

I have never used one of these before so I don't know what the norm is.

 

[hippy]

It sounds like initialisation is doing something. Double-check wiring and crossed-over wires, shorts etc. I'd plug a different LCD in and if that works then the original LCD is probably kaput otherwise, if it does the same, it's more likely software or wiring.

 

[booski]

Just a quick update.

I think I've been a complete fool. I have no idea what I have done, but it suddenly has decided to work!

Tough little thing considering it was originally powered up in reverse!

Oh well, I needn't have bought another LCD last night for £1.44!

Thanks for the help nonetheless though.

 

[hippy]

I have no idea what I have done, but it suddenly has decided to work!

Could be a power-on / initialisation / timing issue; it may be behaving differently if already powered-up and initialised than when powered-on and initialised. That's most often observed when programs work after every download but then don't when turned off and back on again.

 

[Paix]

@Booksi, we had a rabbit once that would go all sullen and off it's food. Take it to the vet and it would suddenly come to life even before it got looked at. I was convinced that it just needed a little more than normal proof of being loved - parting with cash.

It seems that your LCD panel is just like that rabbit. Just don't let the fox get at it . . . All's well that ends well and you have another toy to play with. Everyone wins!

 

[booski]

Possibly! Can't believe it though.

Still, I think something is fried though as the there is a vertical line of pixels missing in the second column in from the right.

But still, it's nice to see that the code works and the PIC can be programmed to use the screen also.