LCD driving trouble
Dwayne Reid email (remove spam text)
<x-flowed>At 10:44 AM 5/30/00 +0100, Andre wrote:
>Hi all !
>I«ve been working on a CPU used to control a high teperature high pressure
>chamber based on a 16C622A.
>It has a LCD display (16x1) been drived using nibbles instead of 8 bits
>words. Unfortunatly I have no more free I/O pins to use.
>The problem is as follow:
>1. When I first turn the CPU ON everything goes right. The LCD shows the
>message it was programed to show.
>2. If I turn the CPU OFF and not after one or two seconds back to ON again
>the LCD shows anything but the message it was programed to show.
>3. If I wait a little bit more (5 sec.) before turning the LCD back to ON
>again everything goes right.
>4. If I turn the CPU OFF and back to ON two times without wait all goes ok.
>I am sening the data without using the LCD R/W pin. The data is sent to
>the display and the program waits it to stabilize before sending the next
My off the cuff suggestion is that you are not properly initing the
LCD. According to specs, you must issue the 'switch to 8 bit mode' *3*
times before switching to switching to 4 bit mode. Repeat: you have to
issue the 'function set' command with the 8 bit mode bit set for a total of
THREE times before changing to 4 bit mode.
You would do this in your PIC init routines after each power up
reset. Give it a try!
Dwayne Reid <planet.eon.net> dwayner
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Celebrating 16 years of Engineering Innovation (1984 - 2000)
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
commercial email nor is intended to solicit commercial email.
In reply to: <firstname.lastname@example.org>
See also: www.piclist.com/techref/io/lcd/pic.htm?key=lcd
You must be a member of the
piclist mailing list
(not only a www.piclist.com member) to post to the