Page 359 - Programming Microcontrollers in C

344 Chapter 6 Large Microcontrollers

putchar(0xd);
putchar(0xa);
}

}
int handle_data(int new_data)
{
static int i=63;
data[i—]=new_data;
i &=63;
return (i==63)?0:i+1;
}
Listing 6-13: Test Program For The Circular Convolution

Then the code to send the data to the circular_conv() is
modified slightly to that shown below.
for(i=0;i<64;i++)
{
/* get new data — use 0x100 for this test */

ip=data+handle_data(0x100);
point[i]=circular_conv(64,ip,32,coef);
}
The value 0x100 is sent into the function handle_data , and
the return is the index into the array where the data was stored in the
array data. When this integer is added to data, which is a pointer to a
type int, the pointer ip will point to the location into the array where
the latest value was stored in memory. Under normal circumstances,
this piece of code would be entered under control of a clock and the
data sent into the routine handle_data() would be new input from
an analog to digital converter. Also, the for statement is not expected
in a practical application. The output from this program is:

2 4 6 8 10 12 14 16
18 20 22 24 26 28 30 32
34 36 38 40 42 44 46 48
50 52 54 56 58 60 62 64
64 64 64 64 64 64 64 64
64 64 64 64 64 64 64 64
64 64 64 64 64 64 64 64
64 64 64 64 64 64 64 64