This will be one of those effective times, I can feel it.  Let’s begin.

First, I’ll direct you to a passage from Neal Stephenson’s Cryptonomicon.  This is a dialogue taking place between the characters of Enoch Root and Randy Waterhouse.  Root speaks first.

“When I phoned you the other day, how did you know it was me?”

“I don’t know. I just recognized you.”

“Recognized me? What does that mean? You didn’t recognize my voice.”

“Is this some roundabout way of answering my question about Athena worship v. Christianity?”

“Doesn’t it strike you as remarkable that you can look at a stream of characters on the screen of your computer–e-mail from someone you’ve never seen–and later ‘recognize’ the same person on the phone? How does that work, Randy?”

“I haven’t the faintest idea. The brain can do some weird–”

“Some complain that e-mail is impersonal–that your contact with me, during the e-mail phase of our relationship, was mediated by wires and screens and cables. Some would say that’s not as good as conversing face-to-face. And yet our seeing of things is always mediated by corneas, retinas, optic nerves, and some neural machinery that takes the information from the optic nerve and propagates it into our minds. So, is looking at words on a screen so very much inferior? I think not; at least then you are conscious of the distortions. Whereas, when you see someone with your eyes, you forget about the distortions and imagine you are experiencing them purely and immediately.”

“So what’s your explanation of how I recognized you?”

“I would argue that inside your mind was some pattern of neurological activity that was not there before you exchanged e-mail with me. The Root Representation. It is not me. I’m this big slug of carbon and oxygen and some other stuff on this cot right next to you. The Root Rep, by contrast, is the thing that you’ll carry around in your brain for the rest of your life, barring some kind of major neurological insult, that your mind uses to represent me. When you think about me, in other words, you’re not thinking about me qua this big slug of carbon, you are thinking about the Root Rep. Indeed, some day you might get released from jail and run into someone who would say, ‘You know, I was in the Philippines once, running around in the boondocks, and I ran into this old fart who started talking to me about Root Reps.’ And by exchanging notes (as it were) with this fellow you would be able to establish beyond a reasonable doubt that the Root Rep in your brain and the Root Rep in his brain were generated by the same actual slug of carbon and oxygen and so on: me.”

I really like this idea.  All of our interactions with another person provide information that is used to form a representation of them in our heads.  If you and I get coffee, or hit a pub, we’ll have some high-bandwidth communication.  You’re seeing me, hearing my voice and my laugh.  But time is scarce, so you and I can’t always be interacting face-to-face.

Then there’s e-mail and blogging.  Interactions lower in bandwidth, but still lending themselves to long-form communication.  As in the story excerpt above, even an email exchange can be enough to form a representation of the author in the reader’s mind.  It just won’t be a complete picture.  Have you ever read a book, then heard the author read it at an event and been surprised by their voice?

I see Twitter as similar to e-mail and blogging (but also different).  Let me explain… no, there is too much.  Let me sum up…

Twitter is a way to provide frequent low-bandwidth data points that help to maintain an accurate “Tom Rep” in your brain.  Reading as other people tweet helps to do the same of them in my own brain.  It can get irksome when one person’s data points are so frequent that it causes others to be missed, but this threshold is pretty high for me.  By using Twitter well, we can keep mental representations of ourselves fresh and accurate.

Which will have to suffice until we’re talking over pints again.

I’ve reached the first milestone: potentiometers for Volume, Tone, and Duration are all responding as expected (after correcting a few mistakes).  Here’s a movie showing how it all currently works!

The toughest bit to get working was the momentary button that will eventually play the currently selected tone.  I had it hooked up to digital pin 13 originally, and it seemed to work for a minute or two.  Then it stopped.  Maybe I had it wired wrong and fried that pin?  Hmm.

So I’ve moved to using pin 3 instead.  And I’m being more careful.

The tones that can be generated are limited to an array I filled with the frequencies of all of the piano keys from G2 to C8.  It felt like a reasonable range to start with, but I’m noticing that the sheer number of frequencies makes it tough to dial-in to an intended note easily!  I might add another pot to control octave, and then just reduce the tone pot to a single octave range.

The construction of the tones themselves is done using Pulse Width Modulation.  This is to say that for tone being created, the microprocessor is pulsing HIGH voltage for half of the frequency length and then LOW voltage for the other half.

For instance, the frequency of the note A4 is 440Hz.  Hz (or Hertz) is a measure of how many cycles of a wave occur per second.  A frequency of 440Hz means that there are 440 wave cycles for each second of sound; conversely this could be understood to mean that one entire wavelength lasts for 1/440th of a second.

Sound waves tend be split into two equal sections: a peak and a valley.  I am able to represent these to the speaker using HIGH and LOW voltage values.  Since each value represents half of the wave, I need to pulse HIGH at for 1/880th of a second (half of 1/440th of a second) and then LOW for another 1/880th of a second.

The processor goes back and forth between sending HIGH and LOW to the speaker for as long as I want the sound to last.

So that’s how the tones work!

Next I will be tuning up the duration, limiting it to quantities that will represent eighth, quarter, half, and whole notes and rests.  And dotted of the same, maybe.  Then I’ll use my last pot to control tempo.

Here is a brief summary describing how everything is set up:

• Rocker switch between digital pin #2 and GND, not currently in use.
• Momentary pushbutton between digital pin #3 and GND, with the pin’s built-in pull-up resistor activated in code.
• 100K Ohm audio taper potentiometer: first lead on digital pin 11 (PWM speaker out), middle lead to speaker, third lead to GND.
• 100K Ohm linear taper potentiometer: first lead on 5V, middle lead to analog pin 0 (tone control), third lead to GND.
• 100K Ohm linear taper potentiometer: first lead on 5V, middle lead to analog pin 1 (duration control), third lead to GND.
• 8 Ohm mini speaker between audio taper potentiometer and GND.

And here’s the code that is currently used to drive it all… Tone_Generator_v1.pde.txt

Enjoy!

Not once have I stepped foot out of my apartment.  Not even into the hallway.

Fortunately I remembered to grab my laptop before I left work on Monday, and have been able to take care of my duties from home.  Perhaps more effectively than usual, what with my swanky dual 19″ LCDs.  Yum.

Planning to vanquish the foul demons that afflict my system tonight, I find myself thinking strangely about tomorrow.  Thoughts like: oh, yeah, I have a car!  Will it still be out there?  On what part of the street did I park it?

I don’t even remember where I parked my car. 

During the last three days the thought of my car did not even enter my mind.  Out of sight, out of something.

I don’t know what the temperature is like outside.  It has been nice and toasty in here, but it could be 35 degrees outside.  All I am sure of is that when I open the window it is colder out there than it is in here.

Well, I have once more kept myself up much later than I ought.  Time to sleep, and see if I can answer some of these burning questions tomorrow.  I am excited to explore… THE OUTSIDE!