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surprising stationary robot success
Monday, December 24 2018
Gretchen spent much of the afternoon enjoying Netflix on our new 55 inch 4K television. The streams seemed to run just fine at HD resolution over our crappy 3.6 Mb connection. If anything, the huge screen made the programming look cheap, but then again it might've actually been cheap. One program Gretchen watched a few episodes of was a mystery series set in the modern west called Longmire, and it looked like a soap opera on our big screen. The acting also seemed a bit wooden, and I don't think that was a result of any of the technology.
Meanwhile, I was moving ahead with my Raspberry Pi/Arduino stationary surveillance robot. I soldered a I2C level shifter onto an Adafruit 16 X 12 bit PWM shield, which would allow the shield to be controlled by I2C commands sent from a 3.3 volt source, in this case a Raspberry Pi Model B. I then added four parallel 4-pin headers to the shield and wired them up to supply 3.3 volt I2C to whatever devices I choose to attach. The first of these was an LM7A temperature sensor. All of these things (the Raspberry Pi, a USB WiFi dongle, the Adafruit Shield, an Arduino Uno, an HD camera, a pan/tilt servo rig, and a LM75A temperature sensor) ended up screwed down to a board together and then interwired everything. That was pretty much all the hardware I needed to assemble for my vision. From there I could turn to proof of communication and then, eventually, to writing some rudimentary software. Amazingly, I was soon able to get all of this stuff working and testable over an SSH session. Using raspistill, I could snap .jpgs at will with the camera and then SFTP them to my computer. Then I used a simple Python program to read temperatures from the LM75A, and it worked from the very first attempt. Later I downloaded an Arduino sketch to test the servos, which responded correctly to commands coming from the Arduino. The only test left then was one of the Arduino running as an I2C slave. I would need that to read analog values (such as from a smoke detection module), since the Raspberry Pi has no analog inputs. But just when everything was coming together, the Raspberry Pi's SD-card based boot volume got corrupted and everything stopped working. I'd expected more trouble of that sort, especially with all the soldering I'd done. Volume corruption almost never happens, but when it does, that's all she wrote. I shouldn't really be surprised to have that happen given all the marginal SD cards I've bought over the years (including a fake 64 GB SD card that actually only had a capacity of 8 GB).
For linking purposes this article's URL is:
http://asecular.com/blog.php?181224 feedback
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