Hello, my name is Judas Gutenberg and this is my blaag (pronounced as you would the vomit noise "hyroop-bleuach").
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$10 logic analyzer
Friday, March 7 2014
As you know, I've been trying to figure out a way to decode the data coming from Meade remote temperature sensors. I have a good collection of 433 MHz receiver boards by various manufacturers, though none of them has been able to output data in a way that matches a similar board inside a Meade weather receiver. Clearly what I needed was a better way to look at the data coming out of such boards. The way I had been "looking" at that data was by playing it through an audio amplifier. Obviously, there was no way to get a sense of the actual data that way. I could only tell that it was coming in three bursts. To examine the data in detail I would need something called a logic analyzer. Traditionally, logic analyzers have been expensive devices similar to multi-trace oscilloscopes. But with advances in computer technology and the standardization of interfaces, they have become cheap boxes with USB interfaces. I managed to find an eight-trace logic analyzer in the NewEgg marketplace that only cost $9.83 (for my application, I only needed to use one trace). I ordered it several weeks ago and then, a week later, received a strange email from the merchant (over in China, of course) asking if I'd received it yet. This caused me to wonder if something suspicious was going on. So I checked that merchant's ratings (something I normally wouldn't remember to do at NewEgg, which I think of more as a reputable store than as a marketplace) and saw that they were terrible. People ordered stuff and it never arrived, or it arrived broken or partially-missing. I'd just about given up on that $10 logic analyzer and had ordered a significantly better one. But wouldn't you know, the $10 one arrived today. It's a little plastic box no bigger than a matchbox car. Plugged into a mini USB cable, a little red light comes on, but that's it. Judging from the pealing paper label, I assumed it was some sort of counterfeit of a real logic analyzer. The label said "Saleae,' which turns out to be a respectable logic analyzer manufacturer. I downloaded their software and installed it, and damned if it didn't immediately recognize my $10 logic analyzer. So I hooked it up to one of my 433 MHz receiver boards and initiated a data capture. Sure enough, it recorded a beautiful string of pulses when the receiver received a broadcast from one of my temperature sensors. Making sense of that data will obviously take some doing. But I have to say I'm impressed that something so cheap and of such dubious provenance seems to do precisely what I need.
This afternoon I went out on another firewood gathering expedition with my new backpack frame, this time venturing a bit further to the west. The air temperature was about ten to fifteen degrees warmer than it had been yesterday, and that difference almost made working outdoors a joy. I felled and bucked a very dry six-inch-thick oak trunk (the dead half of a dual-trunk tree) until my chainsaw's battery went dead. This was the first time I'd ever run out of juice with it (I'd only recharged it once or twice since getting it). Interestingly, the weight of the wood that I carried home was almost identical to what it had been yesterday (~70 pounds).
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