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fox85
Guest
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| unable to get RAND_MAX working |
 Posted: Thu Nov 09, 2006 3:19 pm |
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I am trying to utilize the RAND_MAX function but it doesn't seem to do anything at all. I set up a test to try it out using a 16f690 pic chip with an LCD.
Here is my code:
| Code: |
#include <16F690.h>
#device ADC=8
#include <STDLIB.h>
#fuses INTRC_IO,NOWDT,NOPROTECT,NOMCLR,NOBROWNOUT,NOIESO,NOFCMEN
#use delay(clock=8000000)
#define RAND_MAX 12
#use RS232(Baud=9600,Xmit=PIN_A0)
void test_randoma(int x){
int i;
long randx;
randx = rand();
printf("?f");
delay_ms(200);
printf("test random A");
delay_ms(500);
for(i=0; i<x; i++){
randx = rand();
printf("?f");
delay_ms(200);
printf("%5Lu?a",randx);
delay_ms(1000);
}
}
void test_randomb(int x){
int i;
long randx;
#define RAND_MAX 12
randx = rand();
printf("?f");
delay_ms(200);
printf("test random B");
delay_ms(1000);
for(i=0; i<x; i++){
randx = rand();
printf("?f");
delay_ms(200);
printf("%5Lu?a",randx);
delay_ms(1000);
}
}
void main(void){
#define RAND_MAX 12
printf("?B7F"); // power contrast pin on LCD
delay_ms(500);
printf("?f");
delay_ms(5000);
printf("beginning test");
delay_ms(1000);
while(1){
test_randoma(5);
delay_ms(1500);
test_randomb(5);
}
} |
In this code I used the random call as a long but I also tested it as an int. The code runs fine printing random long values to the LCD but RAND_MAX doesn't cap the random numbers at all. Any suggestions? |
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fox85
Guest
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| RAND_MAX |
| Posted: Thu Nov 09, 2006 3:22 pm |
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| Also, #define RAND_MAX appears twice in this code however I have tried it with #define both only at the top and only in the body of main and neither made any difference. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Nov 09, 2006 3:31 pm |
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Look in this file that you've included:
| Code: | | #include <STDLIB.h> |
Near the start of the file, it defines RAND_MAX:
| Code: |
#ifndef RAND_MAX
#define RAND_MAX 32767
#endif
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The #ifndef statement means it will use the default value, provided
that RAND_MAX hasn't been previously defined, prior to this point.
So if you want to change the default value of RAND_MAX (which is
32767), you need to put in a #define statement with a new value,
and you need to place the statement before the one in stdlib.h.
Currently, you have several of them in random areas of your program.
You should delete those lines and do it like this:
| Code: |
#define RAND_MAX 12
#include <stdlib.h>
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fox85
Guest
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| thanks for the help, working now |
| Posted: Thu Nov 09, 2006 3:43 pm |
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| Thanks, PCM programmer. I had looked over the stdlib file but didn't make the connection regarding the order of my statements in the top. Thanks. |
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