LCD driving trouble
Jilles Oldenbeuving email (remove spam text)
You might want to check the supply voltage to the processor. With some
capacity in your system
supply voltage will not be immediatly 0 V when you switch of the supply.
Let's say the voltage will
be 2.0 V when you switch on the supply again, a brown - out will occur. i.e.
the processor is
plain not running due to the fact that the Vdd didn't reach 0 V... i've seen
this in a consumer product
(vacuum cleaner). When programming your device be sure to set brown-out
detect on (and maybe
adapt your program to this).
By waiting longer before switching on the supply you make sure that Vdd will
reach 0 V, and thus
a brown-out will not occur.....
Van: Andre <ZAZ.COM.BR> acolling
Aan: MITVMA.MIT.EDU < PICLISTMITVMA.MIT.EDU> PICLIST
Datum: dinsdag 30 mei 2000 15:53
Onderwerp: [PIC] LCD driving trouble
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 4
Any comments or sugestions are welcome !!!
See also: www.piclist.com/techref/io/lcd/pic.htm?key=lcd
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