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LCD Problems

 
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LCD Problems
PostPosted: Sun Feb 12, 2006 9:36 pm     Reply with quote
I just graduated from school and I'm working on projects to help advance my knowledge while I'm looking for a job. Currently I'm working on connecting an LCD to a PIC16F874, but I'm not having much luck. I've learned enough about the connections - I'm positive my wiring is correct. But what I'm having trouble with is getting the software to work. My clock is a 20 mhz oscillator, which might be a problem, but other than that I can't understand why this isn't working. My code is below:

Code:
#include <16F874.H>
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#include <stdlib.h>
#include <lcd.c>

main() {

  delay_ms(1000);
  lcd_init();
  delay_ms(1000);

  lcd_putc("\fDoes this work\n");
  //printf(lcd_putc, "Hello World.");
  delay_ms(1000);
}



I'm not exactly sure what the problem is, whenever I run this code the LCD just spits out like 5 or 6 characters (I'm not sure how many, I haven't counted them, but it's the same each time). But the characters themselves is basically a black box, only one dot is missing, so something like this:

.....
....
.....
.....

see how one dot was gone?? I don't know what the problem is. Do I need to manually change the enable pin and make it go from high to low? I can't see how that would be the case because I'm using this function....please help...

-Chris
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Sun Feb 12, 2006 9:51 pm     Reply with quote
Download the Microchip PicDem2-Plus manual here:
http://ww1.microchip.com/downloads/en/devicedoc/51275b.pdf
Go to page 20, and look at the LCD schematic in the upper left corner.
How is your circuit different from this one ?

Note that though they show trimpot R20, on the actual board it is not
installed. Only R5 and R6 are installed.
Guest
PostPosted: Sun Feb 12, 2006 10:18 pm     Reply with quote
According to the LCD.c file, these are what my pins are connected to:

Code:
// As defined in the following structure the pin connection is as follows:
//     B0  enable
//     B1  rs
//     B2  rw
//     B4  D4
//     B5  D5
//     B6  D6
//     B7  D7
//
//   LCD pins D0-D3 are not used and PIC B3 is not used.


Also, although you can use two resisters to do the job, I'm actually using a 10kohm POT. Not that it matters, both ways work.

Let me know if you have any other advice.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Sun Feb 12, 2006 10:32 pm     Reply with quote
Strip your program down to essentials. Also, you didn't post a
#fuses statement. I have added one.

Try this program:
Code:

#include <16F874.H>
#fuses HS, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=20000000)

#include <lcd.c>

void main()
{
lcd_init();

printf(lcd_putc, "Hello World");

while(1);
}
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