LCD Init Problems

[jecottrell]

Hello All,

This is kind of a continuation of this recent topic/problem:

http://www.ccsinfo.com/forum/viewtopic.php?t=29225


What I'm up against now is a random failure of the LCD to display on startup. By that I mean, everything works normally, PIC doesn't hang in the init_lcd function and contrast can be adjusted way up to show all pixels 'filled', but the display isn't showing the expected text just the solid blocks.

If I init the LCD twice prior to the main loop reliability gets better but not 100%. If I put an init_lcd in the main loop where I'm updating the text, I think I can say I get 100% reliability by the third write to the display. Also, if I put a large delay between powering up the LCD and init'ing it doesn't seem to help either.

Restarting is either through pulling the power connection to the board to cycle the power or pushing a reset button. Both cause the problem, so I don't think it's a power up problem?

Could there be a problem with the default port settings on power up that are causing this, and after a few inits it finally gets resolved?

I've also tried several displays with identical results.

Any help would be greatly appreciated.

John

[PCM programmer]

1. What's the LCD manufacturer and part number ?
Do you have a link to the data sheet ?

2. What provides the power supply for this board ?
Is a wall transformer and a voltage regulator ?

3. What LCD driver are you using ? You don't have to post the code,
but tell us which one you are using.

4. Are these tests being done with the LCD power coming from
a transistor and FET circuit as described in your previous post ?
Have you tried disconnecting the LCD from this circuit, and just
use the normal power supply for it ?

[jecottrell]

PCM,

Thanks for taking a look, here is the additional data:

1. Crystalfontz: CFAH1602B-YYH-JPV

http://www.crystalfontz.com/products/1602b-wt/CFAH1602BYYHJPV.PDF

2. 9V Battery or wall wart through a LT1521 LDO. 0.1uF + 10uF on input, 0.1uf + 4.7uF on output. 0.1uF + 10uF at LCD power pin on board. Problem occurs with all varieties of power.

3. CCS lcd.c


4. Yes and yes, with the same erratic results


It looks as though, if I put three lcd_init's 25mS apart, prior to the main loop I get 100% reliability. So it appears to be something with that....


Thanks,

John

[jecottrell]

OK.

I started doing the math, and put 2 and 2 together and figured maybe the 40Mhz clock speed was causing problems. When I change from the PLL to 10Mhz it appears everything works normally with one init_lcd.

Can I modify the driver to put some delays in the functions to slow things down?

Thanks,

John

[PCM programmer]

[jecottrell]

PCM,

Thanks. I think that fixed it.

I didn't go back and look at the functions after the previous post. I'd like to think I would have caught the delay_cycles vs. delay_us....

John