LCD driving trouble
Peter L. Peres email (remove spam text)
I have seen this happen with 2 x 16 LCD. The reason is that the LCD takes
a very long time to decay all its internal voltages. Here are 5 fixes
(which should be applied together for good results):
- Set the B'1000' fixed combination on D0-D3 of the LCD. Refer to the LCD
controller data sheet for why (the code that initializes the display
- Use the 'long' initialization sequence every time (see LCD data sheet).
- Place a small resistor (1-2k) in parallel with the LCD power pins to
help drain the voltage quickly. You can use a low value contrast pot for
this to avoid adding parts. This assumes that you can live with the extra
power drain (2.5-5mA @5V).
- Have a turn-on delay of 0.5 sec at least before talking to the LCD after
- You can save a lot of power by leaving the LCD on and using the display
off command (measure yours), This removes the reset problem if the unit
has soft power control.
See also: www.piclist.com/techref/io/lcd/pic.htm?key=lcd
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