Current state

The changes we made took quite some time to figure out, even though they're actually very simple things. But regardless, the result is a working project.

Transmitter



The iPod connects to a headphone jack, which connects to the ADC pin of the Butterfly. Then bits go flying out of the XBee! The MAX232 level converter is not really visible (it's obscured by the white cable).

Receiver



That hideous jumble of wires is a "bus" from the Butterfly's PORTD to the DAC. The DAC output voltage is connected to the headphone jack, which connects to our speakers. You can't see the battery unit in this picture, but it's the same as the transmitter's: 3 AA batteries. Surprisingly, the receiver can run everything off of 4.5V, including the DAC (5V nominal), speakers (7.5V nominal), Butterfly (3V, we only use two of the batteries for it), and the MAX232. Even then, it only takes something like 100mA to operate. The transmitter is as good or better. We've run the units for hours and they still have not exhausted their first set of batteries.

Audio quality is what you would expect with 8 bit samples at ~8,800 Hz. But it actually sounds pretty decent, if I do say so myself. We even have a lowpass filter set up on the input to the ADC pin on the transmitter. We tell ourselves we can hear a difference.

Range seems to be around 30 feet.

The cool thing about this project is that it's digital information being transmitted. This means that we can do all sorts of stuff other than streaming audio.

Thanks to Scott for the pictures. I should've done a better job of choosing pictures from the set for this post.