|
|
|
fun with I2C
Saturday, February 12 2011
The main thing I hoped to gain with my new solar controller project was an I2C bus, a simple two-wire serial bus for connecting digital electronics together. When combined with ground and +5 volt wires, I2C is a four wire bus, with exact analogs for the four wires in a USB bus. But the protocols are different and it's a much lower-bandwidth bus, so it's best suited to sensors and low-volume data storage. This accords nicely with the needs of my solar controller, which can happily take seconds to arrive at its decisions and doesn't need to sample data more often than every several minutes.
Today I continued building out the new solar controller on a enlarged Olimex 28 pin AVR serial board. After I confirmed that the four analog inputs were working, I attached my first I2C device, a real time clock module. Amazingly, it worked the first time I uploaded an Arduino test-script. This I2C bus was going to make my life easier! By soldering four wires between an existing circuit and something new, I could add vast new capabilities. Well I remember the bad old days of digital electronics, when I had to piece together complex logic using discreet 74LSXX logic chips and carefully solder two ends of every single wire of both the address and the data buses (this often resulted in as many as 56 individual precision solders, though I cheated with memory chips, stacking them one on top of the other and bending out the chip selects). Of course, back in the day we didn't have surface-mount chips with tightly-pitched leads; everything was more-or-less macroscopic and solderable. And 25 years ago, my hands were a bit more precise in their ability to position the tip of a soldering iron. But most of the electronics I work with today is also macroscopic; it's still possible to get chips like the Atmega328 with large through-hole pins pitched at ten to an inch.
As I worked on these things, I listened mostly to sciency and doom-and-gloom lectures from Ted.com, starting with a fun lecture by James Howard Kunstler and following the "other talks" out from there.
For dinner tonight, Gretchen and I went out to our favorite local Indian restaurant, the one in Uptown Kingston, and had an unusually delicious meal. It was Saturday night, so the restaurant had a buffet, but it looked kind of weary, so we ordered from the menu. For the first time when not ordering take-away, I ordered a curry "spiced hot like they do in Bangladesh." Because I was clearly a gringo doing the ordering, they probably didn't spice it quite as hot as they could have, but it was pretty damn hot nevertheless. We also drank a smallish (500 mL) cat-shaped bottle of Riesling we'd brought with it.
For linking purposes this article's URL is:
http://asecular.com/blog.php?110212 feedback
previous | next |
