How to test HD44780 LCD's

charsz · Post by **charsz** » June 18th, 2006, 11:55 pm

Hello,

I bought some 2x16 HD44780 LCD's and have problem with them. Wiring checked many times, and still I get only one fully squared and one blank line on LCD. How could I test them with simple circuit?
I tried to connect just VSS, VCC and VLC and still I'm getting this one full line and one empty. It doesn't fade out. Are they all broken or what?

_X7JAY7X_ · Post by **_X7JAY7X_** » June 19th, 2006, 4:26 am

The blocks that appear at power up are normal. They come from the display driver chip. If you are getting no characters then your wiring is most likely wrong. Another possible problem could be the parallel port. Have you tried a few lcd's or just one?

There is no simple circuit for testing. The easiest way would be using the parallel port.

charsz · Post by **charsz** » June 19th, 2006, 2:13 pm

_X7JAY7X_ wrote:The blocks that appear at power up are normal. They come from the display driver chip.

If I connect only power and contrast voltage these characters should stay on lcd till something send data to chip? Or they should dissapear after short period?

_X7JAY7X_ wrote: If you are getting no characters then your wiring is most likely wrong. Another possible problem could be the parallel port. Have you tried a few lcd's or just one?

Few.

Post by **limbo** » June 19th, 2006, 3:47 pm

The blocks should stay until LCD receives valid (or invalid

) data!