Go Down

Topic: How to read HD44780 LCD programmatically (Read 7647 times) previous topic - next topic

Retroplayer

I didn't. Got pretty far, but simply couldn't convince myself that it was useful at all.

What you are describing could be handled with a simple text buffer. Since you are already in control of what is displayed on the screen, just manipulate it in memory and update or write to external memory.

If you put 'A' in row 1, column 1, you already know what is going to be in row 1, column 1.

I just see no usefulness to this at all.

floresta

Quote
I just see no usefulness to this at all.

When the device was designed, decades ago, there was some usefulness.
I gave the reasons behind the inclusion of this capability two months ago, in the second paragraph of reply # 6.


Don

Retroplayer


Quote
I just see no usefulness to this at all.

When the device was designed, decades ago, there was some usefulness.
I gave the reasons behind the inclusion of this capability two months ago, in the second paragraph of reply # 6.


Don


*Shrug*

No offense, but write it yourself, then. lol

I did not feel that it was useful enough to spend my time writing it, testing it, debugging it, refining it and maintaining it regardless of your reasons. If you do, then write it...

teddyz

There are alot of threads about reading from the HD44780, but I have yet not found a working example.

My reason for wanting this is to verify that the HD44780 is OK or not. I have five 4x20 displays (DMC20481 by Optrex Japan). Of those, I have tested two and not gotten anything on the display. So now I have hooked up one of them using 4-bit mode (I can add four more leads if that helps) and I can connect RW-pin to any IO on my Arduino.

How can I test if my HD44780 is alive or not?

floresta

Quote
... Of those, I have tested two and not gotten anything on the display....
... How can I test if my HD44780 is alive or not?
Connect just the power and contrast pins (pins 1, 2, and 3) and see if, by adjusting the contrast potentiometer, you can display two rows (rows 1 and 3) of boxes.

If that doesn't work you will need a second power supply (a 9v battery will suffice) to provide a negative voltage at the bottom end of the potentiometer, the end that was previously connected to GND.  

There is a slight possibility that you will need the backlight working in order to see anything on the display.  That is common with some of the 'newer' displays, but on your ancient device that is not likely.

Once you are able to display the boxes you can proceed to connect the data and control lines and try to display some text.  If you can't display the boxes then no amount of code will help.

Don

teddyz

Thank you Don!

At -9V I got the boxes. No need reading from HD44780 for me. Atleast not today. :-)

/Dick
!

Go Up
 


Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

Arduino
via Egeo 16
Torino, 10131
Italy