Hd44780 displays

[B]

Has anyone ever had this problem?
I have a HD44780 Lcd 20 * 4 display. It initialises ok, and operates. If i
turn it off, then on before the power caps discharge the display will not
initialise, but has the firts and third line as blocks. It does not
initialise.



Thanks
Darren.

 

[John Woodgate]

I read in sci.electronics.design that B <no_spam@no.com> wrote (in
<4159875b$0$32611$ed2619ec@ptn-nntp-reader02.plus.net&gt about 'Hd44780
displays', on Tue, 28 Sep 2004:

Has anyone ever had this problem?
I have a HD44780 Lcd 20 * 4 display. It initialises ok, and operates. If i
turn it off, then on before the power caps discharge the display will not
initialise, but has the firts and third line as blocks. It does not
initialise.


By doing that you are defeating the initialization process. The voltage

isn't falling far enough to trigger it, but it falls low enough to
mangle the data fed to the two lines.

The simple solution is not to do what you did. If you can't adopt that,
please come back and explain why. You probably need a circuit to crowbar
the supply to the display when the main power goes off, or, if the
display has a 'reset' pin, a reset circuit.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[CBarn24050]

It won't initialise itself from a partial power down/up, you need to do it with
software. The datasheet will give you the correct sequence which you have to
follow to the letter.

 

[Mark Walsh]

"B" <no_spam@no.com> wrote in message
news:4159875b$0$32611$ed2619ec@ptn-nntp-reader02.plus.net...

Has anyone ever had this problem?
I have a HD44780 Lcd 20 * 4 display. It initialises ok, and operates. If i
turn it off, then on before the power caps discharge the display will not
initialise, but has the firts and third line as blocks. It does not
initialise.



Thanks
Darren.

I don't recall the sequence of instructions, but there is a soft reset that
can be done (should be done) when you can't guarentee the power up will
properly reset the display controller. We have lots of displays in
equipment out in remote locations that have to tolerate electrical storms.
A watchdog resets the micro, but we need the soft reset to clean up the
display.

Mark Walsh