receiving 32 bit integer through RS232

sk · Guest

Hi everyone,
I would like to know, is there any way to receive 32bit integers through RS232. I used printf to send the 32 bit integer in hexadecimal format. When I tried to use scanf to receive the 32bit integer, the compiler shows error"UNDEFINED IDENTIFIER SCANF". I could not find the scanf statement in the reference manual also. Is there anyway to receive it.
Thanks for any help
sk

John P · Joined: 17 Sep 2003 Posts: 331

In my humble opinion, you'd do better to break the integer up into 4 bytes and send it that way. It'll send faster, and be much easier to reconstuct the quantity in the processor.

bkamen · Posted: Tue Feb 08, 2005 9:45 pm

For the most part, RS232 is an 8-bit kinda thing unless you start bit banging by hand.

4 bytes is the way to go.

-Ben

Charlie U · Posted: Tue Feb 08, 2005 10:06 pm

When you send the int32 with printf, it is sent as 8 ascii characters. These should be received at the other end in a buffer. These characters could then be copied to a string where the first 2 characters are '0', 'x', followed by the 8 ascii characters of the int32, and terminated with a 0 (null or zero). Next, use atoi32() to convert the string to an int32.

jds-pic · Joined: 17 Sep 2003 Posts: 205

as you've already figured out, you can't send a 32bit value directly -- the value has to be parsed into 8 bit chunks suitable for transmission over RS232. let me give you an analogy... suppose you needed to send an extremely large crate via Fed Ex -- but the 747's that Fed Ex uses can only take a crate of such and such a size, which is smaller than your huge crate. so you need to break your big crate into several pieces that do fit on the 747, transport them via multiple Fed Ex planes, and then reassemble them on the other side once all the planes are in.

algorithmically in pseudo-code, the sender end could look like