LCD Trouble

[Bryan]

I am attempting to interface an LCD (HD44780 based) 16x2 to my PIC18F1320. I enabled use of port B in the CCS driver lcd.c since the PIC18F1320 only has ports A and B available. Here is the code I am using to test the LCD:

#include <18F1320.h>
#include <lcd.c>
#fuses NOWDT,NOPROTECT,NOLVP,NOMCLR,INTRC_IO// CCPB0
#use delay(clock=8000000)
#byte OSCCON=0b01111111 //8 MHz

void main()
{

set_tris_a(0x00);
output_a(0x00);
output_b(0x00);
lcd_init();
output_high(PIN_A0);
lcd_putc("\fHello World!");
}

I am using pin A0 to test whether the LCD is actually getting through the init sequence as it should be, but something strange happens. I turn on Vdd and nothing happens for about 30 seconds, then all of a sudden the LED comes on momentarily then flickers out (although it isn't burning out) and the power supply voltage drops from 5V (which I set it at) to about 1.5V and I cannot change it (I am using a dual variable power supply). Nothing shows up on the LCD screen either. I also noticed that part of the LCD gets very hot once the voltage drops and I would think this would mean something is shorting (pins connected incorrectly), though I have no clue why it would take 30 seconds for this to happen. There is a contrast adjust pin that I just tied to ground, thinking this would give maximum contrast and I would see something if the LCD was powering up correctly, but I see nothing. Any help would be appreciated if anyone has ever experienced anythign like this before!

[akokyaw]

Hi,
Try the command ADCON1 that is actually the register for ADC. I believe that 18F1320 has ADC function at portA and by default portA is set to analog function. In order to drive lcd, you should set portA to digital function. I hope that will help.

Rgds,
ak

[PCM programmer]

1. You're not really setting OSCCON register. The #byte statement
is used to define the address of a register, not to set it to a value.
You need to look up the address of OSCCON in the data sheet
and use that number instead of what you're using. Look in this
section: Memory Organization / Special Function Registers

Then if you need to set OSCCON, do it with a line of code in main().
Treat OSCCON just like any other variable.

Depending on your version of the compiler, you shouldn't have to
set OSCCON. I tested your code with vs. 3.188, and CCS inserts
start-up code that sets OSCCON = 0x70, which is proper for 8 MHz.

2. You're letting your program fall off the end of main(), where it hits
a hidden SLEEP instruction which is placed there by the compiler.
That may not actually be causing your problem.

3. Do you have a series resistor connected to your LED, to limit the
current through it ? (Something in the range from 270 to 47O ohms).

4. If the LCD is getting very hot, it's likely wired incorrectly. I would
look for a reversal of +5 and GND. 16x2 LCD's usually have a dual
row header pin arrangement. One side has all the odd numbered
pins, and the other side has the even numbered pins. Pin one is
indicated by a square pad. The others are round. You may need
a new LCD.

5. With regard to the comment about Port A -- CCS puts in start-up
code to configure it as all digital. I checked vs. 3.188, and at
least in that version, the code is correct.

[Mark]

This is a really old post. Bryan actually posted it a couple of times and has resolved his problem