This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

/* SuperSimpleIR -
 * Bare-minimum no-frills code to interpret input from an IR decoder, using pin change interrupts.
 * Does no fancy decoding - it's up to you to figure out which button corresponds with the
 * output from this snippet. The provided message codes work with an Apple remote, but this is by
 * no means limited to such remotes (for instance, my Yamaha receiver's remote works fine with this).
 * Possible improvements:
 * - Use a timer interrupt instead of timeToCommitMessage. I didn't bother
 *   implementing this as the project I developed this for will need the timer for other tasks.
 * - The message commit code is (barely) vulnerable to concurrency issues if a pulse comes in while
 *   we try to commit a message. In practice I don't think this matters.
 * - It gets confused easily if the signal gets weak and corrupted.
 */

// From the Tiny core.
#include <TinyDebugSerial.h>

TinyDebugSerial mySerial;

// Pin defs.
#define IN_IR 4 // If this is changed, change the code that enables interrupts.

#define IR_MSG_PLUS               2011287570
#define IR_MSG_MINUS              2011279378
#define IR_MSG_REW                2011238418
#define IR_MSG_FFWD               2011291666
#define IR_MSG_PLAYPAUSE          2011242514
#define IR_MSG_MENU               2011250706
#define IR_MSG_REPEAT_LAST_BUTTON 0

// After this much time has elapsed after the last transition, consider the
// message complete.
#define MSG_COMMIT_TIME_MICROSEC 30000

enum IRProtocolState { Idle, Building };

unsigned long timeOfLastIRPinChange;  // Time when the last pin change happened on the IR decoder.
unsigned long timeToCommitMessage;    // Time after which we should consider the message complete.
unsigned long message;                // Workspace where the message is built up.
IRProtocolState irProtocolState;      // What our protocol decoder is doing.

void processIRMessage(long message);

ISR(PCINT0_vect) {
  boolean isPinHigh = digitalRead(IN_IR);
  long currentTime = micros();
  long microsSinceLastChange = (currentTime - timeOfLastIRPinChange);
  timeOfLastIRPinChange = currentTime;
  
  // Bump up the commit time, since we got a level change.
  timeToCommitMessage = MSG_COMMIT_TIME_MICROSEC + timeOfLastIRPinChange;
  
  if (!isPinHigh)
  {
     // Going low.
    if (microsSinceLastChange < 700)
    {
      // Space
      message = message << 1;
    }
    else if (microsSinceLastChange < 2000)
    {
      // Mark.
      message = message << 1;
      message |= 1;
    }
    else if (microsSinceLastChange < 20000)
    {
      // First LOW.
      message = 0;
      irProtocolState = Building;
    }
  }
  
}

void setup()
{ 
  mySerial.begin(9600);
  mySerial.println("IR test up.");

  timeOfLastIRPinChange = micros();
  timeToCommitMessage = -1;
  irProtocolState = Idle;
  
  GIMSK = _BV(PCIE);    // Enable pin change interrupt
  PCMSK = _BV(PCINT4);  // Enable the interrupt for only pin 4.
}

void loop() {
  // Check to see if we can commit a message. If so, process it.
  if (micros() >= timeToCommitMessage && irProtocolState == Building)
  {
    long localMessage = message;
    message = 0;
    irProtocolState = Idle;
    processIRMessage(localMessage);
  }
}

void processIRMessage(long message)
{
  switch (message)
    {
      case IR_MSG_PLUS: mySerial.println("Plus"); break;
      case IR_MSG_MINUS: mySerial.println("Minus"); break;
      case IR_MSG_REW: mySerial.println("REW"); break;
      case IR_MSG_FFWD: mySerial.println("FFWD"); break;
      case IR_MSG_PLAYPAUSE: mySerial.println("Play/Pause"); break;
      case IR_MSG_MENU: mySerial.println("Menu"); break;
      case IR_MSG_REPEAT_LAST_BUTTON: mySerial.println("(repeat last)"); break;
      default: mySerial.print("Unknown code: "); mySerial.println(message); break;
    }
}

There isn't much to it, just an ATtiny84 and a couple connectors. The software is actually compatible with most AVRs, so you can use whatever AVR you have handy if you're willing to rework the PCB (they just need enough pins: 7 at bare minimum if you get rid of the status LED). You'll notice a USB plug in there. This thing does not speak USB, only mouse PS2. Thing is, most USB mice can act as PS2 devices (those little PS2->USB adapters are just wires). So instead of fiddling with adapters, I opted to directly use a USB plug. Beware though that some really modern mice don't speak PS2. If your mouse is worth less than $5, you're set . Here's a view from the other side:

Youtube goodness:

I've made all the code/schematics/PCB layouts available as open-source hardware (TAPR Open Hardware License, www.tapr.org/OHL), so grab your copy here:
Mac2PS2.zip

Note! If you'd be interested in buying a kit or fully assembled product from me, drop me a line (YouTube comment would be best). If there's at least a little bit of demand, I'll set something up. It'll be cheap; I don't plan on making money from this

Here is the breakout board I made for this project (with the addition of a spot for a larger bypass cap, which I found necessary).

WS2801 Breakout 3d view

Download: WS2801_Breakout

WS2801 Breakount by Giacomo Ferrari is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Based on a work at giferrari.net.

yep, seriously

The bottom of the expansion board.

Here is the top of the board.

Front view.

Normal stuff. Some SIMMs, some glue logic... and... WAIT.

Nope, this isn't the Mac's mainboard!

Yes, this Frankenstein has its own 68k. Could it be disabling the Mac's 68k to replace it with this monstrosity? Who knows. There's also this extra 2x13 header on the board that goes out to an extra DB-25 on the back of the Mac (you can see it just to the right of the expansion board's 68k on the below picture). Absolutely no idea what that does. Edit: It's a SCSI port.
Anyway, here's some pics of the thing installed on the Mac's mainboard.

Installed front view

Installed side view.

More glamour shots of various parts:

Some extra info.

SIMMs.

Glue logic. Can't find info on those 2 AMD devices.

Some custom Calmos ASIC.

So, has anyone seen this thing before? Were they popular? It does seem to work - my 512k is reporting 2 megs of ram.

http://www.youtube.com/watch?v=5Eyk8veiGB4

Z2->Arduino cable

As for the OS I used on the Zipit: z2sid. It's my distro of choice because it's Debian (meaning apt-get works!) and gcc works. To get avrdude (the flashing program), I just did apt-get install avrdude. I whipped up this little script so I don't have to type out the rather long avrdude commands:

avrdude -v -patmega328p -cstk500v1 -P/dev/ttyS2 -b57600 -D -Uflash:w:$1:i

Save that as flash.sh, chmod it +x, and use (./flash.sh my-sketch.hex). You might want to change the -patmega328p to whatever is appropriate for you. Note that the Z2 doesn't have a DTR line, meaning auto-reset won't work. You'll have to reset the Arduino manually, then run avrdude. Timing takes a bit of practice.

The product.

As for the design itself, I've got a bit more than a classic SOHA amp here (the VU meter stuff I talked about in my previous post). Unfortunately, I still haven't received all the parts for that (they're from Soviet Russia. Seriously.). So I'll hold off on posting the CAD designs and parts list until I know it all works. Here's some pics from the build, though.

Front resist. Turned out pretty well.

Back resist. Not bad, but some pinholing. It's a ground plane though - not the end of the world.

Front with silkscreen. It actually stuck this time

Back. Yup, pinholes. Blast.

Front populated. Tube section on the left; solid state on right.

Looks much cooler with the tube

Obligatory long-exposure night shot.

Test setup. Not pictured: me rocking out (thankfully).

Laying this thing out was a bit of a pain due to those large caps. Also, the kicad library archive didn't have modules for most of these parts. Oh well. Here's what I came up with:

SOHA power supply board. About 3.5" by 2".

Here are some pics from the build:

Some boards with juicy connectors. Salvage time.

Whoo, free (to me) connectors!

Always, ALWAYS make sure your parts fit your layout!

Toner transfer via laminator.

All etched.

All populated and working!

I've uploaded a KiCad project containing a schematic and the board layout.

SOHA power supply board layout by Giacomo Ferrari is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Download.

Parts! I love parts. I got a bunch of 'em in the mail for the headphone amp:

Transformers! The left one is for a VU meter I'm thinking of building (I'll write about it if it works), the right one is a 30VCT, 1000mA toroid for the SOHA itself (bigger than the classic SOHA's 400mA, since I'm adding some accessories that need power).

Autobots, move out!