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pre assign value to bit in a struct

 
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mds



Joined: 06 Nov 2005
Posts: 29

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pre assign value to bit in a struct
PostPosted: Tue Sep 07, 2010 6:03 pm     Reply with quote

Hi all,
Can you pre assign a value to a bit inside a struct at compile time?

I often pre assign my vars with values when defining them

such as
Code:

int8 fred=0;

Id like to do something similar with the struct byte.
Code:

struct dbg_typ{
unsigned fspr     :7;      ///<Spare
unsigned f_rep_en :1;  ///<Enable report printing
}dbgrep;


Id like to set f_rep_en to be true on start up.

Obviously at some startup config section in my code I could simply say
Code:

dbgrep=0x80;


But I thought it would be neater, and less chance of being forgotten if I did it at the same point the struct is defined.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Tue Sep 07, 2010 8:08 pm     Reply with quote

The demo program below shows how to initialize a structure in C.
The output of the program is:
Quote:

fspr = 2a, f_rep_en = 01


Code:

#include <18F452.h>
#fuses XT,NOWDT,PUT,BROWNOUT,NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)

struct dbg_typ{
unsigned fspr     :7;
unsigned f_rep_en :1;
}dbgrep = {0x2A, 1};

//======================================
void main(void)
{

printf("fspr = %x, f_rep_en = %x \r", dbgrep.fspr, dbgrep.f_rep_en);

while(1);
}
 
mds



Joined: 06 Nov 2005
Posts: 29

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PostPosted: Tue Sep 07, 2010 9:01 pm     Reply with quote

haahh many thanks sir.
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