Microcontrollers have been with us for many years now, but only recently have they become simple enough for weekend dabblers to use. To get to this point, several improvements to their ease of use had to be developed, the most important of which was in-circuit flash reprogramming, which meant the software in the chip could be reprogrammed easily by someone developing algorithms on the fly, by trial and error. Also, well-documented development systems had to be developed and simplified. Finally, the microcontrollers and their environments had to become cheap. All these advances have been best-realized with the Arduino, which has been around now for over three years. An Arduino has been controlling the collection of solar hot water here for nearly two years (I'd first learned about the Arduino in an issue of Make Magazine).
The main downside of the Arduino environment is a consequence of its microcontroller, the Atmega168. This chip only has 28 pins, and this means that the Arduino only has six analog inputs and 14 digital outputs (several of which can serve as PWM quasi-analog outputs). This number of programmable pins seemed like more than enough back when I was first setting up my Arduino-based solar heat controller system, but now I've maxed out. To open up a pair of unused digital pins, today I ended up doubling up the task of one of the pins so that it would serve both as a pushbutton reader and as the signal to turn on one of four indicator LEDs (this has the side effect of lighting that indicator whenever the button is held down, something that is actually kind of satisfying).
I wanted to open up these digital pins because I wanted to connect a number of devices that can communicate through something called an I2C bus. I2C buses work like low-speed USB buses, allowing complex chips on the same circuit board to communicate with one another using a minimum of connections. It's the perfect system for someone like me, who has to hand wire individual strands of conductive wire between circuits. Back when I was a teenager, I used to wire up static RAMs to conventional microprocessor buses, and this meant eight wires for the data bus, several wires for control pins, a ground wire, a five volt VCC wire, and then as a many as 15 wires for the address bus. Being able to connect a complex new circuit using only two signal wires, a ground, and a power wire seems effortless by comparison.
As I did these things this afternoon, I didn't yet know that the Arduino environment has built-in hardware support for the I2C bus, but this support requires the use of analog pins 4 and 5, both of which I am already using for analog inputs. If I want to get I2C working with digital lines, I'll have to do the whole thing in software. Bleh.
Tonight Gretchen and I went across the Hudson for dinner and an evening of early 20th-Century Russian emigree music. We ate at the China Rose in Rhinecliff, a reliably transcendant dining experience. The Rhinecliff China Rose might well be the best restaurant within 30 miles of our house. It's definitely the best Chinese restaurant I've ever eaten in, even if it doesn't have an especially Chinese ambience. This evening Gretchen noticed that one of the staff who appeared briefly near the bar was actually Asian.
The concert was in the big weird stainless steel concert hall at Bard College, and we got there late, only seeing the last half of the first half of the show. For the second half, Bard College President (and general-purpose Swiss Army Renaissance man) Leon Botstein did all the conducting, but before he started, he provided one of his rambling (though informative) stories, in this case about the obscure composer Nikolai Obukhov. I enjoyed the Obukhov work that the orchestra then proceeded to play, though I found the little woodwind noises that punctuated the eerie atmospherics of the strings off-putting, reminding me of the sound effects in a cutesy Disney animation.
On the way to Bard tonight we stopped at Poet's Walk to walk the dogs, and I shot a little video.
Talking about Eleanor's not-entirely perfect knee.
