The Smell of Molten Projects in the Morning
Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Who’d’a thunk it?
The neutral conductor is down to its last three strands:
Perhaps the power drop got snagged twice, because there’s a splice only a few feet away:
Spotted overhead on Redondo near Rt 376 during an evening walk. I reported it using Central Hudson’s dead streetlight page, because there seems no other way to get their attention. It may be the homeowner’s responsibility, in which case a second splice will surely appear after the next power outage.
The driver gave us plenty of room, which is always nice:
But then the SUV turned into the Maloney Rd entrance to the Dutchess Rail Trail:
Which was specifically designed to exclude motor vehicles:
Later, I was told it’s an “allowable access” for Water Authority vehicles and, in any event, because their SUV didn’t leave the biggest ruts and tracks, they think it’s all good:
The ramp joins the trail at an acute angle, so the SUV required some backing & filling to get around:
Then it’s an easy drive to the water meter about 2500 feet down the trail:
There’s an Official Vehicle Access gate one mile south of the Maloney ramp that’s about 3800 feet from the water meter. I’m told they use the Maloney ramp to reduce the distance they drive on the rail trail; evidently, destroying the entrance Just Doesn’t Matter.
I’m trying to develop an attitude between Zen and apathy, with just enough indifference to not care when somebody tells me how wonderful things will be in the future.
A small rabbit, occasionally seen about the back yard and within the garden, met an untimely end:
We credit one of the neighborhood hawks or owls.
Over the course of the next few days, the corpse lost more of its stuffings and eventually vanished.
Perhaps a similar event produced the bunnyless head we saw a while ago.
Go, birds, go!
After several years of seeing few-to-no Monarch butterflies, last year we managed to save a single Monarch egg, raise the caterpillar, and release it:
This year, we’ve seen more, if not many, Monarchs in flight. They’re not abundant, but perhaps there’s hope.
A Monarch evidently laid eggs in our milkweed patch, with at least two offspring surviving:
We decided to let them seek their own destiny; may the odds be ever in their favor …
Two lines in /boot/config.txt enable the I2C hardware and set the I2C bus speed:
dtparam=i2c_arm=on dtparam=i2c_arm_baudrate=200000
However, the actual SCL frequency comes from dividing the CPU’s core clock by an even integer, so you can’t always get what you want. The Pi 3 ticks along at 1.2 GHz (actually 1.1 GHz, because marketing) from a core clock of 550 MHz, so a 200 kHz clock calls for a 2750 divider: 550 MHz / 2750 = 200 kHz.
Actually measuring the SCL frequencies suggests something else is going on:
D0, the bottom trace, is SCL, D1 is SDA, and D2 is a trigger output not used in this setup. The yellow analog trace is the current in the SCL line between the Pi and the BNO055, about which more later.
So a 200 kHz nominal frequency produces a 125 kHz actual frequency.
The BNO055 pulls the clock low (“clock stretching”), which can (and does) cause problems, but it’s not active during the main part of the transfer where the Pi determines the SCL frequency.
More measurement along those lines produces a table:
| CPU Core Clock: | 550 | MHz | |
| I2C SCL kHz | |||
| Nominal | Ratio | Actual | Ratio |
| 250 | 2200 | 156.20 | 3521 |
| 200 | 2750 | 125.00 | 4400 |
| 150 | 3667 | 92.59 | 5940 |
| 125 | 4400 | 78.12 | 7040 |
| 100 | 5500 | 62.50 | 8800 |
| 50 | 11000 | 31.25 | 17600 |
| 25 | 22000 | 15.63 | 35189 |
| 10 | 55000 | 6.25 | 88000 |
Apparently, the code converting the nominal I2C rate in config.txt uses a table of divider values intended for another CPU core clock. AFAICT, the boot code could divide the actual core clock by the desired I2C frequency to produce the appropriate value.
I have no particular desire to Use The Source to figure out what’s going on …
[Update: Perhaps this comes along with CPU clock throttling due to temperature. For completeness, I should dump the temperature and actual clock speed.]
This corner on Maloney Rd is almost exactly one mile from the end of Hudson Valley Regional Airport Runway 24:
So it’s not unusual to ride under a small plane on final approach. Having a Gulfstream V fly directly overhead, however, is a real attention-getter:
What’s not at all obvious from the picture is how big a GV looks when seen directly overhead through those trees just ahead on the corner where our paths crossed. There’s a 360 ft (above sea level) hill directly on the flight path, so it’s at maybe 600 ft ASL and 400-ish ft AGL.
Thrust-reversal thunder rolled over us 50 seconds later, as we rode up the rail trail access ramp. Figuring we’re 15 sound-seconds from the strip, the GV was 30 seconds from touchdown.
One of the two air pockets in the token padding had popped:
Fortunately, they were plastic bottles with rugged contents, so I suppose the packaging was up to the task.
The Smell of Molten Projects in the Morning 