Problem with LCD and Start Up

[paul borgmeier]

Paul's Theory - It sure sounds like to me that during the 0-3 second period after you turn off the power (and before you turn it on again), the power supply voltage drops low enough to reset the pic but not low enough to reset the LCD. After 4 seconds off, I am guessing the voltage decays enough to reset the processor AND the LCD - the LCD might be in the brown area until 4 seconds passes. You can:

1)Use a scope to measure the voltage after you turn off the power and see what it does.
2)Reset the LCD in software as partially described earlier in the week here
http://www.picbasic.co.uk/forum/showthread.php?t=4851
3)Change your power supply so that the voltage decays faster when the power is removed.
4) Board change – move the power for the LCD (not backlight if you have one) to an open pin on the PIC and control it there. (I know your board is does but ... if you need to make a change later)

the LCD show chinese

Oh, I am guessing it is japanese you are seeing and not chinese - most controllers have japanese as a second set of data characters built in.

Just my 2 cents worth

[mister_e]

chinese or japanese, it's greek to me

[savnik]

chinese or japanese, it's greek to me

maybe japanese

[savnik]

I change the pic16f84a with 16f628a and now work OK
why this difference;
my config is

[mister_e]

Brown out detect is the answer.

Maybe the power-up timer could help on your grandpa F84. But more than likely, a capacitor between MCLR and gnd will work... have a look to the F84 datasheet. i'm pretty sure they show you some RESET circuit there.

It's no coincidence why most PIC have a Brown-Out detect feature now

I usually set both to ON

[savnik]

Maybe the power-up timer could help on your grandpa F84.

I test but no help.

a capacitor between MCLR and gnd will work

I have capacitor.

The only solution for me is to replace the 16f84a with 16f628a , or to use a MCP100-101