Pointer in functions problem...

[micro]

Hi!,

I have some problems with using pointer in functions.
I have written a simple code snipped that use pointers but it does not work.

#include <18f458.h>
#include <string.h>
//#device *=16
#fuses H4,NOWDT,NOPROTECT,NOBROWNOUT,NOPUT,NOLVP
#use delay(clock=40000000)
#use rs232 (baud=9600, xmit=PIN_C6, rcv=PIN_C7,ERRORS)



byte WriteIntoBuff(int16 Length, unsigned char *BuffAddr)
{

int16 count;

for(count=0;count<Length;count++)
{
Buff[PT_WrIndex]=*BuffAddr;
BuffAddr++;
}
}


void main(void)
{

int16 tx_count;
unsigned char s[100];
int16 adres;
adres=&s[0];
strcpy(s,"This is a sample text string for PIC18F458 UART0 Tx test");

txcount=strlen(s);

WriteIntoPumpTxBuff(tx_count,s);

.
.
.
.

}

[alexz]

What exactly does not work?
Have you declare the function prototype as
byte WriteIntoBuff(int16 Length, unsigned char *BuffAddr) ;
Where do you actually call this function?
_________________
Alex

[Guest]

I have made a mistake in my question. Correct code is below

#include <18f458.h>
#include <string.h>
//#device *=16
#fuses H4,NOWDT,NOPROTECT,NOBROWNOUT,NOPUT,NOLVP
#use delay(clock=40000000)
#use rs232 (baud=9600, xmit=PIN_C6, rcv=PIN_C7,ERRORS)



byte WriteIntoBuff(int16 Length, unsigned char *BuffAddr)
{

int16 count;

for(count=0;count<Length;count++)
{
Buff[PT_WrIndex]=*BuffAddr;
BuffAddr++;
}
}


void main(void)
{

int16 tx_count;
unsigned char s[100];
int16 adres;
adres=&s[0];
strcpy(s,"This is a sample text string for PIC18F458 UART0 Tx test");

txcount=strlen(s);

WriteIntoBuff(tx_count,&s[0]);

.
.
.
.

}

In the code, WriteIntoBuff does not work. It should be take "s" array and put it in to "Buff" array but it does not. What is wrong with it..?

[alexz]

Try to cal the function this way:
WriteIntoBuff(tx_count,s[0]);
in other words no '&', as you already pass the pointer.
_________________
Alex

[Guest]

I have tried but it does not work again. Actually, a pointer variable requieres an adsress as a value. So it seems , & operator is required but it does not work. I am confused.

[alexz]

you definitely do not need the '&'.
Try this:

WriteIntoBuff(tx_count,s);

byte WriteIntoBuff(int16 Length, unsigned char *BuffAddr)
{

int16 count;

for(count=0;count<Length;count++)
{
Buff[PT_WrIndex]=*BuffAddr[0];
}
}

If that does not work, declare this array as global and do not pass it.
_________________
Alex

[Mark]

[treitmey]

I always thought an array is the same as a pointer...

referance K&R second edition page 98 - 99.

I think passing the address of "&n[2]"
should work the same as n
when n is an array...n[5]


(if you don't know what K&R is...it shows I'm getting old)

[alexz]

Sorry, I meant no '&' when passing just the name of the array
_________________
Alex

[JPA]

[treitmey]

I think we are saying the same thing.
Yes the name is an address to ellement 0.
If you have a funtion that requires an address,... for example an address to an int8.

int8 tmp[3];

Then you can pass in the array name.

function(tmp)
or
function(&tmp[2])

This is how I use it.

[Guest]

[treitmey]

yup,.. bad array example. (fixed)