C code of simple Receiver - c

Question

I have this code of a transmitter and I have a problem where when I get input from my transmitter I save it in a char array "rec" and after I have finished receiving I compare it with my other arrays and base on that comparison I light up a bulb in portb. But the code gives me no errors and no bulb lights (the connection works I've tried it) it has something to do with the comparing arrays part. Am I doing this right? Thank you
char rec[3];
char cmp1[]= "1000";
char cmp2[]= "1010";
char cmp3[]="1111";
char cmp4[]="1001";
int i=0;
int beginrecord;
void main(void)
{
TRISB=0;
TRISD=0;
TRISC=255;
PORTC=0;
PORTB=0;
while(1)
{
if(PORTC==1)
{
rec[i]=1;
i++;
beginrecord = 1;
delay_ms(1);
}
if (PORTC==0 && beginrecord==1)
{
rec[i]=0;
i++;
delay_ms(1);
}
if(i==4) {
beginrecord = 0;
i = 0;
if(rec == cmp1){
portb = 0x01;}
else if(rec == cmp2){
portb = 0x02;}
else if(rec == cmp3){
portb = 0x04;}
else if(rec == cmp4){
portb = 0x08;}
}
}
}

Answer 1

You must use strcmp(rec, cmp1) == 0 instead of rec == cmp1.
The way you do it now, you compare only the pointers, which are never the same.
And are you sure that your port returns a character 1or 0 and not the values 0/1?
In that case your comparison also wouldn't work.
Some other issues with your code:
I assume that the char form the port is a binary value and not an ASCII character.
If it is indeed an ASCII character and you use strcmp() then you must add a zero byte at the end of the buffer.
If you receive multiple bytes and not bits, you must use memcmp() instead of strcmp(). In that case your intialisation of cmpX would be also wrong. If it are bits you receive, you would want to combine them into bytes before comparing (assuming a serial port).
PORTC is always 0, so it can not become 1 in your code.
You seem to have mixed case PORTB vs. portb.
your variables have no type.

Answer 2

Here you are declare three cmp[] of char type which is a string so it is like "1000". it is 4 byte data. and your rec[3] is only 3 byte. i think you try to compare a int type. like
1001 == 1001 in binary
Declare them as unsigned int then try to compare.
And make all your values full 8 bit like 00001000b not 1000.
or may be i get it wrong.

Answer 3

There are a number of issues that confuse your goal - see above comment, but I've tried to address them below.
Rather than accumulate the rec as an array, the bits are accumulated in an int. This simplifies the compares to your original style.
beginrecord needed initialization. Variables were brought into a local scope.
Cleaned up the indentation.
const int cmp1 = 8; // "1000";
const int cmp2 = 10; // "1010";
const int cmp3 = 15; // "1111";
const int cmp4 = 9; // "1001";
void main(void) {
TRISB = 0;
TRISD = 0;
TRISC = 255;
PORTC = 0;
PORTB = 0;
int i = 0;
int beginrecord = 0;
int rec = 0;
while (1) {
if (PORTC == 1) {
rec <<= 1; /* rec = rec * 2 */
rec |= 1;
beginrecord = 1;
delay_ms(1);
i++;
}
else if (PORTC == 0 && beginrecord == 1) {
rec <<= 1;
delay_ms(1);
i++;
}
if (i == 4) {
if (rec == cmp1) {
PORTB = 0x01;
} else if (rec == cmp2) {
PORTB = 0x02;
} else if (rec == cmp3) {
PORTB = 0x04;
} else if (rec == cmp4) {
PORTB = 0x08;
}
beginrecord = 0;
i = 0;
rec = 0;
}
}
}