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A real stupid problem

 
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Wolf



Joined: 23 Sep 2011
Posts: 32

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A real stupid problem
PostPosted: Mon Oct 03, 2011 5:54 pm     Reply with quote
Hey!

Ok here is my problem....I'm trouble shooting my circuit board, and all the bits on Port A, E, and 1 bit on C go directly to a socket so I can drop in an LCD screen. However, one of the bit's isn't working properly PIN_A4, or pin 6 positioned on PIC16F877. So I have hooked all the wires to LED's so I can see them work but I cannot make PIN_A4 work for the life of me. I looked at the datasheet and it says it's a bi-directional pin so I don't know.

here is my code:
Code:

#define LCD_DB7         PIN_A0
#define LCD_DB6         PIN_A1
#define LCD_DB5         PIN_A2
#define LCD_DB4         PIN_A3
#define LCD_ENABLE      PIN_A4
#define LCD_RS         PIN_C2
#define BACKLIGHT_RED   PIN_E0
#define BACKLIGHT_GREEN   PIN_E1   
#define BACKLIGHT_BLUE   PIN_E2

#include <16F877.h>
#fuses HS,NOWDT,NOPROTECT
#use delay(clock=20000000) //Crystal Oscillator @ 20MHz
//#use rs232(baud=9600,xmit=PIN_C6,rcv=PIN_C7)

void StartupSettings();

void main() {
   StartupSettings();

   while(1) {
      output_bit(LCD_DB7, 1);
      output_bit(LCD_DB6, 1);
      output_bit(LCD_DB5, 1);
      output_bit(LCD_DB4, 1);
      output_bit(LCD_ENABLE, 1);
      output_bit(LCD_RS, 1);
      delay_ms(1000);
      output_bit(LCD_DB7, 0);
      output_bit(LCD_DB6, 0);
      output_bit(LCD_DB5, 0);
      output_bit(LCD_DB4, 0);
      output_bit(LCD_ENABLE, 0);
      output_bit(LCD_RS, 0);
      delay_ms(1000);   
   }

   return;
}

void StartupSettings() {
   set_tris_a(0x00);
   set_tris_c(0x00);
   set_tris_e(0x00);

   return;



Any ideas?
bungee-



Joined: 27 Jun 2007
Posts: 206

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PostPosted: Mon Oct 03, 2011 6:14 pm     Reply with quote
Look at the datasheet again on page 42. There is a line on page 41
Quote:
The RA4/T0CKI pin is a Schmitt Trigger input and an open-drain output.
pay attention on underlined text Wink

I had the similar experience the first time I came across this particular port. Embarassed
For most application you can simply put 10k resistor to the 5V line.
Wolf



Joined: 23 Sep 2011
Posts: 32

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PostPosted: Mon Oct 03, 2011 6:42 pm     Reply with quote
Oh damn it! I guess I need to start cut up or solder parts off my circuit board. Thank you
asmallri



Joined: 12 Aug 2004
Posts: 1635
Location: Perth, Australia

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PostPosted: Mon Oct 03, 2011 10:59 pm     Reply with quote
Wolf wrote:
Oh damn it! I guess I need to start cut up or solder parts off my circuit board. Thank you


No you just need to add a pull-up resistor.
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