Hi-Tech C delay problem (PIC16F877)

juvenile86 said:

Hi, I am new to PIC programming with C language..
My program is simple, which is to set Port B as output, and make a LED connected on any of the Port B pins blink with an interval of 1 second.

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#include <htc.h>
__CONFIG (0x3F32);

void delay(unsigned long x);

void main()
{
TRISB = 0x00;
PORTB = 0;

while(1)
{

PORTB = 0xFF;
delay(1000);
PORTB = 0x00;
delay(1000);
}
}

void delay(unsigned long x)
{
for(;x>0;x--);
}
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I am able to compile and write the HEX code into the PIC microcontroller, but I got output voltage of about 2.45V in all of the port B pins. Anyone have idea what is going wrong here?

I tried to use MikroC built-in delay library, Delay_ms(1000) and everything works fine. So I can be pretty sure there is no problem on my hardware connections. I am using Crystal Oscillator of 20MHz anyway.

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BeeBop said:

Even if you use the largest number for a long - 0xFF - your delay is only going to be about 13 milliseconds: 65535 cycles / (5,000,000 cycles/second) = 0.013107seconds.

Your delay at 1000 cycles / (5000000 cycles/second) = 0.0002 seconds is much too short to see the LED flash.

If you look at the built in delay you used in Mikro, it wants a parameter for the number of milliseconds to delay, not cycles. You need to use a nested for or something else to get a longer delay.

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__DELAY_MS, __DELAY_US
Synopsis
__delay_ms(x) // request a delay in milliseconds
__delay_us(x) // request a delay in microseconds
Description
As it is often more convenient request a delay in time-based terms rather than in cycle
counts, the macros __delay_ms(x) and __delay_us(x) are provided. These macros
simply wrap around _delay(n) and convert the time based request into instruction
cycles based on the system frequency. In order to achieve this, these macros require
the prior definition of preprocessor symbol _XTAL_FREQ. This symbol should be
defined as the oscillator frequency (in Hertz) used by the system.
An error will result if these macros are used without defining oscillator frequency
symbol or if the delay period requested is too large.
See also
_delay()

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MOVLW 0x06 ; Configure all pins
MOVWF ADCON1 ; as digital inputs

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juvenile86 said:

I tried to make PORT A as digital output
Still gives me the same problem, I see the LED flash in an interval of less than 1 second
I think I should be other value rather than 5000 in the nested loop condition?

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#include <htc.h>
__CONFIG (0x3F32);

void delay(unsigned long x);


void main()
{
ADCON1 = 0x06;
TRISA = 0x00;
PORTA = 0x00;
TRISB = 0x00;
while(1)
{
PORTB = 0xFF;
delay(1000);
PORTB = 0x00;
delay(1000);
}
}

void delay(unsigned long x)
{
unsigned long i;
for(i=0;i<50000;i++)
for(;x>0;x--);
}

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#include <htc.h>
__CONFIG (INTIO & WDTDIS & MCLRDIS & UNPROTECT);

#define eeney_on RC0
#define meeney_on RC1
#define miney_on RC2
#define moe_on RC3
void time_out(void)
{
unsigned short a;
for (a=0; a<=7000; a++){
}
}
void init_(void)
{
TRISC = 0;
PORTC = 0;
ANSEL = 0;
}

void main()
{
init_();

while (1)
{

miney_on = 1^miney_on;
time_out();
meeney_on = 1^meeney_on;
time_out();
eeney_on = 1^eeney_on;
time_out();
moe_on = 1^moe_on;
time_out();

}
}

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juvenile86 said:

May I know why is it 50000 as I need to explain this to the supervisor as part of my project.

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