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Random Number Generator Help

 
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Megadave



Joined: 04 Jan 2011
Posts: 4

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Random Number Generator Help
PostPosted: Tue Jan 25, 2011 12:03 pm     Reply with quote
Hello

I am using a random number generator that allows me to generate a number within a specific range. The routine works great but I need to use it on a 16f688. Unfortunately the routine uses a lot of ROM not leaving enough room for the other functions. I have identified the section that is causing the high ROM usage which is the division of a float number. Without the (float) the random number generator does not work. Does anyone know of a better way of doing this or better yet doing float point math without using float?

Thanks

Code:


#define  READ_SEED                read_eeprom32(2)
#define  SAVE_SEED(x)            write_eeprom32(2,x)

int16 random(int min,int max)
{
   int16 rand;                                                                  // Declare a temporary 16-bit variable
   max = (max + 1);                                                             // Increment max so that max value is used otherwise max-1 is performed
   seed = READ_SEED;                                                            // Get last known seed value from NV memory
   seed = seed * 1103515245 + 12345;                                            // Calculate new seed value
   SAVE_SEED(seed);                                                             // Save seed value in NV memory
   rand =(int16) (seed >> 16) % 32767;                                          // Generate a random number
   return((int16)min + rand *((max - min)/(float)32767));                         // Return random number between specified range                   
}

[/quote]
Megadave



Joined: 04 Jan 2011
Posts: 4

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PostPosted: Tue Jan 25, 2011 12:10 pm     Reply with quote
I figured it out! If I do this it works!

Code:

return ((int16)rand%(max-min+1)+min);
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