1. Connect the RSSI pin (pin 6) to a digital pin on your microcontroller.
2. Use this line of code in your Arduino loop:

   rssiDur = pulseIn(digitalPin, LOW, 200);

pulseIn returns the duration of a pulse (specified HIGH or LOW) in microseconds (µs).  The 200 is a timeout value in µs—it waits this long to see if there’s going to be a pulse.  Since the XBee’s RSSI PWM period is 200µs, we want to wait at most that long to see if there’s a pulse at all.

Since this function gives you a duration, it’s up to you to map that to a value relevant to your program.  Since the maximum duration of the pulse would be 200µs, you could map that to your logical maximum.

EggBeater uses the intuitive power of rhythm to let anyone control the playback of music. Shaking this small, wireless device in regular patterns can automatically adjust the tempo and timing of loops. Just start playing the EggBeater just as you would a traditional shaker, and listen as the song slows down as you slow down, or speed up as you do!

EggBeater uses an accelerometer coupled with an XBee radio to send your movements to PureData, where they detect your downbeats and rhythmic tempo. The software can then control playback within PureData or send OSC or MIDI messages to other platforms.

Here’s a short video courtesy of Lee-Sean:

ATID – PAN ID
ATDH/DL – Destination address high/low: which local address to send ADC data
ATMY – Local address of this unit

ATD0…D8 – digital pins I/O enable
ATP0…P1 – PWM output enable
ATIU – I/O output enable (UART) – send out through serial
ATIA – I/O input address – address to pay attention to for serial output
ATIT – ADC Samples before TX
ATIR – ADC Sample rate (ms)

ATBD – Baud Rate: 3 = 9600, 7 = 115200
ATWR – Write parameter values

Interesting note from the manual: “The maximum sample rate that can be achieved while using one A/D line is 1 sample/ms or 1 KHz (Note that the modem will not be able to keep up with transmission when IR & IT are equal to “1”).”

Here we are initially testing the fans and arduino program with a simple digital momentary switch:

We used an array of TIP120 transistors to control the 12v fans with the 5v Arduino control signals:

We added LED indicators in parallel with the transistor’s control input and linked my keyboard’s home row keys to the array:

Patrick has been working on a Processing interface that retrieves the number of hits a search term returns on a variety of newssources. More to follow!

After some initial tests blinking an LED, I decided to make a little sinusoidal pulse-width modulator and blink two LEDs:

Pulse-Width Modulation of LEDs

If you watch it you can see the LEDs blink faster and faster and then slower and slower (the avi’s framerate of ~15 of course interferes with this).  The relevant code is:

blinkFreq = ((sin((i * PI / 180))+1) / 2) * freqMod;
...
digitalWrite(ledPin, HIGH);
digitalWrite(ledPin2, LOW);
delay(blinkFreq / 2); 
digitalWrite(ledPin, LOW);
digitalWrite(ledPin2, HIGH);
delay(blinkFreq / 2);

where i is incremented in the Arduino loop and reset after 360.  I could have just used radians but then I’d be incrementing a float value or something so… meh.

I’m not sure if there’s a better or more logical PWM algorithm, I haven’t tried looking one up as this basically does the trick.