This article is literally the reason why people crave summary, because it was so content-free that it was a waste of my time to have read it all. It was a lecture extolling the virtues of repetition while simultaneously displaying none of them.
Readit Newsjames_a_craig commented on Compression culture is making you stupid and uninteresting maalvika.substack.com/p/c... · Posted by u/kjhughes
james_a_craig commented on You Must Listen to RFC 2119 ericwbailey.website/publi... · Posted by u/pavel_lishin
I didn't know RFC 2119 by number, but it was the first one I ever read. What was your first RFC experience?
RFC1459, the IRC one. I wrote the QuakeNet channel services once upon a time.
seems since it's a float it's only 32-bits, and the representation of both 3.14159274101257324219 and 3.14159265358979323846 is the same in IEEE-754: 0x40490fdb
though I agree that it is odd to see, and not sure I see a reason why they wouldn't use 3.14159265358979323846
Yeah, it’s as if they wrote a program to calculate pi in a float and saved the output. Very strange choice given how many places the value of pi can be found.
That is a very 'childhood exposure to 8 digit calculators' thing to notice.
Childhood exposure to pi generation algorithms; the correct version above was from memory.
For some reason the value of Pi given in the C++ code is wrong!
It's given in the source as 3.14159274101257324219 when the right value to the same number of digits is 3.14159265358979323846. Very weird. I noticed when I went to look at the C++ to see how this algorithm was actually implemented.
https://github.com/alexandrefrancois/noFFT/blob/main/src/Res... line 31.
james_a_craig commented on Canon EF and RF Lenses – All Autofocus Motors exclusivearchitecture.com... · Posted by u/ExAr
How could they then tell to what distance they're focused?
I used to have two Ultrasonic lenses, the 17-40/4L and the 17-55/2.8. They both had distance scales which would move around as the lens focused.
My current Olympus lenses have a focus-by-wire manual mode, with a distance scale on the barrel. The camera also reports the focus distance in the EXIF. Are these just vague ballparks?
Some - not all - of the EF lenses have a distance encoder as well. It's fairly approximate; I think it exists mostly for the benefit of the flash system, which needs a rough starting point for the distance in some of the open-loop modes.
For the current Olympus ones, I think there's a broadly similar encoder on the ones with proper manual focus scales, and the pure fly-by-wire ones reset focus at connection so the camera can work it out.
There's a list of the EF lenses and which forms of distance information they provide here: https://web.archive.org/web/20130425064359/http://www.lenspl...
james_a_craig commented on Can you get root with only a cigarette lighter? da.vidbuchanan.co.uk/blog... · Posted by u/1317
Since he’s using a Piezo lighter, shouldn’t it be just a single DC pulse like discharging a capacitor?
Even your example of discharging a capacitor can end up with a pulse both directions, caused by the inductance of the wires.
In this specific situation, there's no common reference level, and so the induced pulse will go both directions. You can think of this as being about the edges of the pulse being the parts that actually cause radio to be transmitted, and there's both a positive-going edge and a negative-going edge on a pulse.
james_a_craig commented on Can you get root with only a cigarette lighter? da.vidbuchanan.co.uk/blog... · Posted by u/1317
Can someone explain why the EMI would cause a Bitflip and not always a high read? Why would a pulse invert the signal that’s read? Don’t the voltages effectively get added?
Sign matters as well as magnitude. The pulse created will have both a positive and negative part - waveform sort of like --^v-- and so you can get either direction bit flip. It's not equivalent to connecting a battery to the pin; EMI's more like AC in that it goes both directions.
james_a_craig commented on Agilent 2000a / 3000a Oscilloscope NAND Recovery salvagedcircuitry.com/200... · Posted by u/sharpshadow
Yes, I'd expect better (though maybe not necessarily 50dB+). Troubleshooting:
1. First suspect is always a bad calibration -- they tend to be unstable in addition to incorrect, but if you have anything with known(-ish) S parameters you can check for correctness too.
2. Second step is to put it in TDR mode and watch to see where the TDR changes. That's where your problem is.
3. A trip through the test set with a torque wrench is a good way to not just check the connections but also calibrate your intuition about the couplers/mixers, which should help interpret #2. You can loosen connectors in sequence and watch them spike on TDR to zero in on the actual problem.
As it happens, I was comparing my 8510C + 8517B to a FieldFox recently and I took some drift measurements, although those were on a short rather than a load. The 8510C blew the FieldFox out of the water, lol. Given the TDR, this might be because the standard itself was temperature sensitive and the FieldFox ports are piping hot, but still.
https://jjoonathan.github.io/plot_drift.html
In case they are useful, here are a bunch of different standards measured by the two instruments.
https://github.com/jjoonathan/cal-std-8510-fieldfox/blob/mai...
EDIT: Also worth mentioning, I recently upstreamed my nice 8510C driver into scikit-rf!
https://scikit-rf.readthedocs.io/en/latest/api/vi/generated/...
Thanks for the suggestions - I'll definitely have a poke at it in TDR mode, that's a good plan.
Thanks also for the scikit-rf driver - I've an 8753ES as well, and I've used scikit-rf with that, but not yet with the 8510.
The example further down has "down" not "dawn" in the poem.
For these to be their hero image examples, they're fairly poor; I know it's a significant improvement vs. many of the other current offerings, but it's clear the bar is still being set very low.