Page 370 - Programming Microcontrollers in C

Numeric Decoding 355

if(isdigit(c=(*sa>>4)+’0'))
number[i++]=c;
else if(c==’0'+0xa)
number[i++]=’0';
if(isdigit(c=(*sa&0xf)+’0'))
number[i++]=c;
else if(c==’0'+0xa)
number[i++]=’0';
sa++;
}
number[i++]=’\n’;
number[i++]=0;
}
Listing 7-3: Numeric Decoding Routine
In this function the output data is called number[] and the in­
put is s[]. The encoded data in s[] is converted one BCD 4-bit
field at a time to ASCII characters. In the event that a character re­
ceived has a value ‘0’+0xa, it is then a character zero or ‘0’. Each
byte is converted from two 4-bit BCD values to two ASCII charac­
ters that represent the proper digits.
The test program for this routine is a combination of the encode
test routine with one to decode the encoded data. As one would ex­
pect, when both the encode and the decode routine are used together,
the result is correct. This observation is true on either the Intel or the
Motorola style chip. The endian-ness of the chip is immaterial when
the entire encode/decode operation is completed.

#include <stdio.h>
#define ARRAY_SIZE 100
int decode(unsigned M[],char *s);
int encode(char *a,unsigned *array,int length);

main()
{
char a[ARRAY_SIZE] ;
int c,i=0;
unsigned array[ARRAY_SIZE];
char s[ARRAY_SIZE];