Question

I’m trying to make some communication for my PIC devices and I use UDP for it.
I may send anything to socket, when i send one char like ‘R’ or any other. code understands it and everything works okay, but when im trying to send integer it doesnt work.

static UDP_SOCKET   MySocket;
BYTE                i;

This works:

if(!UDPIsGetReady(MySocket))
            return;

    UDPGet(&i);
if(i == 'R')    SetDCPWM1(255);

UDPGet(&i);
if(i == 'G')    SetDCPWM1(155);

This code doesn’t work:

UDPGet(&i);
    SetDCPWM1(255-atoi(i));

It compiles, it doesnt crash, it just doesnt work.
The problem is a can send and recieve letters ( chars) but i cant do the same with integers. Like i may send ‘R’ and i recieve it, but i cant send ‘1’ or ’20’, but i really want to send an integer from 0 to 255.

Answer 1

First, the atoi function wants a string, and you are supplying it with a single byte. Secondly, atoi only accepts digits, if the value you receive is a non-digit then it would have returned zero.

I suggest you try this instead:

UDPGet(&i);
if (isdigit(i))
    SetDCPWM1(255 - (i - '0'));

The i - '0' converts an ASCII digit to the actual value. I added the if statement to make sure that the received digit really is a digit, otherwise the calculation would be wrong and may even end up negative number.