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[I posted this to the Arduino developer’s mailing list, but figured others might find it useful too]

When I first started with Arduino, I thought Serial.available() was a very loose wrapping of the RXC bit in the USCRA register, i.e. if I didn’t get data out of there fast, it’d be gone. That led to convoluted code like:

 if( Serial.available() ) {
   val1 = Serial.read();
   while( !Serial.available() );
   val2 = Serial.read();
   // and so on
 }

Yuck. So you end up designing protocols that are too terse. Or maybe you think you need to buffer so you don’t lose it:

 while( Serial.available() ) {
   commandbuffer[i++] = Serial.read();
 }

Then parsing becomes a two step process: read serial, parse buffer. Confusing to newbies perhaps, but at least it allows for a better protocol down the line. (And descend into madness as you gaze into the maw of strtok())

Because Serial contains these big comfy buffers, we often don’t need a second buffer to let us easily implement good protocols. My current favorite is to do something like this:

 // protocol is "CCaaaa", two bytes of command, four bytes of args
 if( Serial.available() >= 6 ) {  // command length is 6 bytes
   cmd0 = Serial.read();
   cmd1 = Serial.read();
   arg0 = Serial.read();
   arg1 = Serial.read();
  // ...etc...
 }

I don’t think I’ve seen any Serial examples that check for a specific number of bytes available. It’s really handy.

Implementing a human-friendly protocol like “command arg0 arg1 arg2”, where command and args are space-separated strings like “servo 12 0xff”, is currently hard with Serial. I do this right now with a 2nd buffer and lots of C hackery:

 char* cmdbuf; char c; int i;
 while( Serial.available() && c!= '\n' ) {  // buffer up a line
   c = Serial.read();
   cmdbuf[i++] = c;
 }

 int i = 0;
 while( cmdbuf[++i] != ' ' ) ; // find first space
 cmdbuf[i] = 0;          // null terminate command
 char* cmd = cmdbuf;     //
 int cmdlen = i;         // length of cmd

 int args[5], a;         // five args max, 'a' is arg counter
 char* s; char* argbuf = cmdbuf+cmdlen+1;
 while( (s = strtok(argbuf, " ")) != NULL && a < 5 ) {
   argbuf = NULL;
   args[a++] = (byte)strtol(s,NULL,0); // parse hex or decimal arg
 }
 int argcnt = a;         // number of args read

This sort of functionality would be great in a library I think. Maybe not in Serial, but a core class.

Any other protocols people like to use and the Arduino code they use to do it?

This is the best toolchest ever, if you do electronics or other small tasks.

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I like the stock iPhone headset. They sound okay as headphones, their mic is pretty good, and setup is much easier than with a Bluetooth headset. Plus they’re pretty cheap at $29. I also liked the stock iPod headphones, for similar reasons. I’m clumsy with headphones and tend to break or lose them. But these stock headsets stand out. The white headphone cables has become part of the Apple marketing message that I’d rather not take part of. So all I want is a black version of the Apple headsets. Since no one sells that, guess I’ll have to make my own. After trying many different substances (PlastiDip, black shoe polish, vinyl dye, & regular MarksALot), the best solution appears to be Sharpie Magnums.

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