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const char pointer problem

 
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Raul
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const char pointer problem
PostPosted: Wed Jan 08, 2003 2:48 pm     Reply with quote

I'm writing a driver for a custom display which uses a menu system. I defining my text library I decided to use constant character arrays for my text. I then attempt to point to the individual characters for the printing of text. I am using version 3.129 of the compiler and am programming for a PIC18F6720. Here is what I am having problems with.

// In the header file
const char test1[] = "TEST";

void Print_String(const char *ch);

// In function library
void Print_String(const char *ch)
{
int8 x = 0;
while(ch[x] != NULL)
{
w_data = (int)ch[x];
wr_data(); // Sends data to display
x++;
}
}

// Somewhere in code
Print_String(test1);

Now when I try to compile, the compiler stops when it gets to my function declaration, more specifically at the 'char' declaration and I get a message that says 'Expecting a , or )'. I've used this method with a couple other compilers and one being Microchips C17 and it worked fine. Is there a fix or some work around for this?
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Original Post ID: 10543
PCM programmer



Joined: 06 Sep 2003
Posts: 20318

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Re: const char pointer problem
PostPosted: Wed Jan 08, 2003 3:08 pm     Reply with quote

:=I'm writing a driver for a custom display which uses a menu system. I defining my text library I decided to use constant character arrays for my text. I then attempt to point to the individual characters for the printing of text.
------------------------------------------------------
CCS doesn't allow pointers to constant strings.
If you want to pass a pointer, you first have
to copy the string into a ram array by using
the strcpy() function.

But you can still use constant strings.
The following program shows how you could
send the string to an RS-232 terminal, or
to an LCD.

Also, the printf() function can have its
output redirected to another function.
See the manual for info on this.


#include "c:\program files\picc\devices\16F877.h"
#fuses HS,NOWDT,NOPROTECT,PUT,BROWNOUT, NOLVP
#use Delay(clock=8000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)

#include <lcd.c>

const char test1[] = "TEST";

//===============================================
void main()
{
printf(test1);
lcd_putc(test1);


while(1); // Prevent PIC from going to sleep
}
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This message was ported from CCS's old forum
Original Post ID: 10544
johnpcunningham
Guest







Re: const char pointer problem
PostPosted: Wed Jan 08, 2003 3:09 pm     Reply with quote

This compiler does not allow pointers to constants. You can use an addressing mode to send the characters.

EXAMPLE:

const char line_1[] ="my data";
char i = 0;

while( i != sizeof(line_1)
{
write_data(line_1[i++]);
}
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Original Post ID: 10545
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