Akkana's Musings on Open Source Computing and Technology, Science, and Nature.
Tue, 12 Feb 2019
A while back, Dave ordered a weather station.
His research pointed to the
Ambient Weather WS-2000 as the best bang for the buck as far as accuracy
(after it's calibrated, which is a time consuming and exacting process
where you compare readings to a known-good mercury thermometer, a process
that I suspect most weather station owners don't bother with).
It comes with a little 7" display console that sits indoors and
reads the radio signal from the outside station as well as a second
thermometer inside, then displays all the current weather data.
It also uses wi-fi to report the data upstream to Ambient and,
optionally, to a weather site such as Wunderground.
(Which we did for a while, but now Wunderground is closing off
their public API, so why give them data if they're not going to
make it easy to share it?)
Having the console readout and the Ambient "dashboard" is all very
nice, but of course, being a data geek, I wanted a way to get the data
myself, so I could plot it, save it or otherwise process it. And
that's where Ambient falls short. The console, though it's already
talking on wi-fi, gives you no way to get the data. They sell a
separate unit called an "Observer" that provides a web page you
can scrape, and we actually ordered one, but it turned out to be
buggy and difficult to use, giving numbers that were substantially
different from what the console showed, and randomly failing to answer,
and we ended up returning the observer for a refund.
The other way of getting the data is online. Ambient provides an API
you can use for that purpose, if you email them for a key. It
mostly works, but it sometimes lags considerably behind real time, and
it seems crazy to have to beg for a key and then get data from a
company website that originated in our own backyard.
What I really wanted to do was read the signal from the weather
station directly. I'd planned for ages to look into how to do that,
but I'm a complete newbie to software defined radio and wasn't
sure where to start. Then one day I noticed an SDR discussion
on the #raspberrypi IRC channel on Freenode where I often hang out.
I jumped in, asked some questions, and got pointed in the right direction
and referred to the friendly and helpful #rtlsdr Freenode channel.
An Inexpensive SDR Dongle
On the experts' advice, I ordered a
Blog R820T2 RTL2832U 1PPM TCXO SMA Software Defined Radio with 2x
Telescopic Antennas on Amazon. This dongle apparently has better
temperature compensation than cheaper alternatives, it came with
a couple of different antenna options, and I was told it should
work well with Linux using a program called
Indeed it did. The command to monitor the weather station is
rtl_433 -f 915M
rtl_433 already knows the protocol for the WS-2000,
so I didn't even need to do any decoding or reverse engineering;
it produces a running account of the periodic signals being
broadcast from the station. rtl_433 also helpfully offers
-F csv options, along with a few other formats.
What a great program!
JSON turned out to be the easiest for me to use; initially I thought
CSV would be more compact, but rtl_433's CSV format includes fields
for every possible quantity a weather station could ever broadcast.
When you think about it, that makes sense: once you're outputting
CSV you can't add a new field in mid-stream, so you'd better be
ready for anything. JSON, on the other hand, lets you report
just whatever the weather station reports, and it's easy to parse
from nearly any programming language.
Testing the SDR Dongle
Full disclosure: at first,
rtl_433 -f 915M wasn't showing
me anything and I still don't know why. Maybe I had a loose connection
on the antenna, or maybe I got unlucky and the weather station picked
the exact wrong time to take a vacation. But while I was testing,
I found another program that was very helpful in testing whether
my SDR dongle was working: rtl_fm, which plays radio stations.
The only trick is finding the right arguments,
since the example from the man page just played static.
Here's what worked for me:
rtl_fm -f 101.1M -M fm -g 20 -s 200k -A fast -r 32k -l 0 -E deemp | play -r 32k -t raw -e s -b 16 -c 1 -V1 -
That command plays the 101.1 FM radio station. (I had to do a web search
to give me some frequencies of local radio stations; it's been
a long time since I listened to normal radio.)
Once I knew the dongle was working, I needed to verify what frequency
the weather station was using for its broadcasts.
What I really wanted was something that would scan frequencies around
915M and tell me what it found. Everyone kept pointing me to a program
called Gqrx. But it turns out Gqrx on Linux requires PulseAudio and
absolutely refuses to work or install without it, even if you have no
interest in playing audio. I didn't want to break my system's sound
(I've never managed to get sound working reliably under PulseAudio),
and although it's supposedly possible to build Gqrx without Pulse,
it's a difficult build: I saw plenty of horror stories, and it
requires Boost, always a sign that a build will be problematic.
I fiddled with it a little but decided it wasn't a good time investment.
I eventually found a scanner that worked:
It let me set limiting frequencies and scan between them, and by
setting it to accumulate, I was able to verify that indeed, the
weather station (or something else!) was sending a signal on 915 MHz.
I guess by then, the original problem had fixed itself, and after that,
rtl_433 started showing me signals from the weather station.
It's not super polished, but it's the only scanner I've found that
works without requiring PulseAudio.
That Puzzling Rainfall Number
One mystery remained to be solved. The JSON I was getting from the
weather station looked like this (I've reformatted it for readablility):
"time" : "2019-01-11 11:50:12",
"model" : "Fine Offset WH65B",
"id" : 60,
"temperature_C" : 2.200,
"humidity" : 94,
"wind_dir_deg" : 316,
"wind_speed_ms" : 0.064,
"gust_speed_ms" : 0.510,
"rainfall_mm" : 90.678,
"uv" : 324,
"uvi" : 0,
"light_lux" : 19344.000,
"battery" : "OK",
"mic" : "CRC"
This on a day when it hadn't rained in ages. What was up with that
"rainfall_mm" : 90.678 ?
I asked on the rtl_433 list and got a prompt and helpful answer:
it's a cumulative number, since some unspecified time in the past
(possibly the last time the battery was changed?) So as long as
I make a note of the rainfall_mm number, any change in
that number means new rainfall.
This being a snowy winter, I haven't been able to test that yet:
the WS-2000 doesn't measure snowfall unless some snow happens to melt
in the rain cup.
Some of the other numbers, like uv and uvi, are in mysterious unknown
units and sometimes give results that make no sense (why doesn't
uv go to zero at night? You're telling me that there's that much UV
in starlight?), but I already knew that was an issue with the Ambient.
It's not rtl_433's fault.
I notice that the numbers are often a bit different from what the
Ambient API reports; apparently they do some massaging of the numbers,
and the console has its own adjustment factors too.
We'll have to do some more calibration with a mercury thermometer
to see which set of numbers is right.
Anyway, cool stuff! It took no time at all to write a simple client
for my WatchWeather
web app that runs rtl_433 and monitors the JSON output.
I already had WatchWeather clients collecting reports from
Raspberry Pi Zero Ws sitting at various places in the house with
temperature/humidity sensors attached; and now my WatchWeather page
can include the weather station itself.
Meanwhile, we donated another
station to the Los Alamos Nature Center,
though it doesn't have the SDR dongle, just the normal Ambient console
reporting to Wunderground.
[ 13:20 Feb 12, 2019
More tech |
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Sun, 03 Feb 2019
I was hurrying to check in some tweaks to the BillTracker before
leaving to join some friends for dinner when I noticed
some beautiful clouds over the Sangre de Cristos.
"That's a spectacular lenticular!" I exclaimed, grabbing the camera.
The clouds got even better ten minutes later as the sunset turned the
clouds salmon-pink, but alas by then we were pulling up to a friend's
driveway and didn't have a clear view, and by the time I did, I'd lost
When I offloaded the photos from the camera's SD card this morning
to see how the photos came out, I found some older photos from our
snowstorm a few weeks ago. In particular, a photo of that curly dragon-droop
glacier above the den deck after it fell. Before and after:
[ 17:58 Feb 03, 2019
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Fri, 25 Jan 2019
For the last few weeks I've been consumed with a project I started
last year and then put aside for a while: a bill tracker.
The project sprung out of frustration at the difficulty of following
bills as they pass through the New Mexico legislature. Bills I was
interested in would die in committee, or they would make it to a
vote, and I'd read about it a few days later and wish I'd known
that it was a good time to write my representative or show up at
the Roundhouse to speak. (I've never spoken at the Roundhouse,
and whether I'd have the courage to actually do it remains to be
seen, but at least I'd like to have the chance to decide.)
New Mexico has a Legislative web site
where you can see the status of each bill, and they even offer a way
to register and save a list of bills; but then there's no way to
get alerts about bills that change status and might be coming up for debate.
New Mexico legislative sessions are incredibly short: 60 days in
odd years, 30 days in even. During last year's 30-day session,
I wrote some Python code that scraped the HTML pages describing a bill,
extract the useful information like when the bill last changed
status and where it was right now, present the information
in a table where the user could easily scan it, and email the user a
Fortunately, the nmlegis.gov site, while it doesn't offer raw data for
bill status, at least uses lots of id tags in its HTML which make them
relatively easy to scrape.
Then the session ended and there was no further way to test it,
since bills' statuses were no longer changing. So the billtracker
moved to the back burner.
In the runup to this year's 60-day session, I started with Flask, a
lightweight Python web library I've used for a couple of small
projects, and added some extensions that help Flask handle tasks
like user accounts. Then I patched in the legislative web scraping
code from last year, and the result was
The New Mexico Bill Tracker.
I passed the word to some friends in the League of Women Voters and
the Sierra Club to help me test it, and I think (hope) it's ready for
There's lots more I'd like to do, of course. I still have no way of
knowing when a bill will be up for debate. It looks like this year
the Legislative web site is showing committ schedules in a fairly
standard way, as opposed to the unparseable PDFs they used in past years,
so I may be able to get that. Not that legislative committees actually
stick to their published schedules; but at least it's a start.
New Mexico readers (or anyone else interested in following the
progress of New Mexico bills) are invited to try it. Let me know about
any problems you encounter. And if you want to adapt the billtracker
for use in another state, send me a note! I'd love to see it extended
and would be happy to work with you. Here's the source:
BillTracker on GitHub.
[ 12:34 Jan 25, 2019
More politics |
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Fri, 18 Jan 2019
My machine has recently developed an overheating problem.
I haven't found a solution for that yet -- you'd think Linux would
have a way to automatically kill or suspend processes based on CPU
temperature, but apparently not -- but my investigations led me
down one interesting road: how to write
a Python script that finds CPU hogs.
The psutil module can get a list
of processes with
psutil.process_iter(), which returns
Process objects that have a
Great! Except it always returns 0.0, even for known hogs like Firefox,
or if you start up a VLC and make it play video scaled to the monitor size.
cpu_percent() needs to run twice,
with an interval in between:
it records the elapsed run time and sees how much it changes.
You can pass an interval to
(the units aren't documented, but apparently they're seconds).
But if you're calling it on more than one process -- as you usually
will be -- it's better not to wait for each process.
You have to wait at least a quarter of a second to get useful
numbers, and longer is better. If you do that for every process on the
system, you'll be waiting a long time.
cpu_percent() in non-blocking mode.
Pass None as the interval (or leave it blank since None is
the default), then loop over the process list and call
proc.cpu_percent(None) on each process, throwing away the
results the first time.
Then sleep for a while and repeat the loop: the second time,
cpu_percent() will give you useful numbers.
'''Return a list of processes using a nonzero CPU percentage
during the interval specified by delay (seconds),
sorted so the biggest hog is first.
proccesses = list(psutil.process_iter())
for proc in proccesses:
proc.cpu_percent(None) # non-blocking; throw away first bogus value
procs = 
for proc in proccesses:
percent = proc.cpu_percent(None)
procs.sort(key=lambda x: x, reverse=True)
if __name__ == '__main__':
prohogscs = hoglist()
for p in hogs:
print("%20s: %5.2f" % p)
It's a useful trick. Though actually applying this to a daemon
that responds to temperature, to solve my overheating problem, is more
complicated. For one thing, you need rules about special processes. If
your Firefox goes wonky and starts making your X server take lots of
CPU time, you want to suspend Firefox, not the X server.
[ 15:54 Jan 18, 2019
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Sun, 13 Jan 2019
And the snow continues to fall. We got a break of a few days, but
today it's snowed fairly steadily all day, adding another
-- I don't know, maybe four inches? Snow is hard to measure because
it piles up so unevenly, two inches here, eight there.
The hiking group I'm in went snowshoeing up in the Jemez last week -- lovely!
The shrubs that managed to stick up above the snow all wore coats
of ice, which fell by afternoon, littering the snow around them with
an extra coat of glitter.
And it was lovely here too, with a thick blanket of snow over everything.
(I need to get some snowshoes of my own, to make it easier to explore
the yard when conditions get like this, otherwise the snow would be
thigh-deep in places. For the hike last week, I borrowed a pair.)
And, of course, there's the never-ending fascination of watching
icicles, snow glaciers moving down the roof, and, this time, huge
curving icicles growing downward above the den deck. They hung more
than four feet below the roof before they finally separated and
fell with a huge THUMP!, leaving a three-foot-high pile
of snow that poor Dave had to shovel (I helped with shoveling
at first, until I slipped and sprained my wrist; it's improving,
but not enough that I can shovel ice yet).
Images of the snowstorm and the showshoe hike:
Snowstorms in January 2019.
[ 16:00 Jan 13, 2019
More misc |
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Thu, 10 Jan 2019
Years ago, I saw someone demonstrating an obscure slide presentation
system, and one of the tricks it had was to let you draw on slides
with the mouse. So you could underline or arrow specific points,
or, more important (since underlines and arrows are easily included
in slides), draw something in response to an audience question.
Neat feature, but there were other reasons I didn't want to switch to
that particular slide system.
Many years later, and quite happy with my home-grown
for HTML-based slides, I was sitting in an astronomy panel discussion
listening to someone explain black holes when it occurred to me:
with HTML Canvas being a fairly mature technology, how hard could
snippet that creates a canvas on top of the existing slide, plus
some basic event handling and drawing code that surely someone else
has already written.
Curled up in front of the fire last night with my laptop, it only took a
couple of hours to whip up a proof of concept that seems remarkably usable.
I've added it to htmlpreso.
I have to confess, I've never actually felt the need to draw on a slide
during a talk. But I still love knowing that it's possible.
It'll be interesting to see how often I actually use it.
To play with drawing on slides, go to my
and, on any slide, type Shift-D.
Some color swatches should appear in the upper right of the slide,
and now you can scribble over the tops of slides to your heart's content.
[ 14:39 Jan 10, 2019
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Sun, 06 Jan 2019
About fifteen years ago, a friend in LinuxChix blogged about doing the
"50-50 Book Challenge". The goal was to read fifty new books in a year,
plus another fifty old books she'd read before.
I had no idea whether this was a lot of books or not. How many books
do I read in a year? I had no idea. But now I wanted to know.
So I started keeping a list: not for the 50-50 challenge specifically,
but just to see what the numbers were like.
It would be easy enough to do this in a spreadsheet, but I'm not
really a spreadsheet kind of girl, unless there's a good reason to
use one, like accounting tables or other numeric data. So I used
a plain text file with a simple, readable format,
like these entries from that first year, 2004:
Dragon Hunter: Roy Chapman Andrews and the Central Asiatic Expeditions, Charles Gallenkamp, Michael J. Novacek
Fascinating account of a series of expeditions in the early 1900s
searching for evidence of early man. Instead, they found
groundbreaking dinosaur discoveries, including the first evidence
of dinosaurs protecting their eggs (Oviraptor).
Life of Pi
Uneven, quirky, weird. Parts of it are good, parts are awful.
I found myself annoyed by it ... but somehow compelled to keep
reading. The ending may have redeemed it.
The Lions of Tsavo : Exploring the Legacy of Africa's Notorious Man-Eaters, Bruce D. Patterson
Excellent overview of the Tsavo lion story, including some recent
findings. Makes me want to find the original book, which turns
out to be public domain in Project Gutenberg.
- Bellwether, Connie Willis
What can I say? Connie Willis is one of my favorite writers and
this is arguably her best book. Everyone should read it.
I can't imagine anyone not liking it.
If there's a punctuation mark in the first column, it's a reread.
(I keep forgetting what character to use, so sometimes it's a dot,
sometimes a dash, sometimes an atsign.)
If there's anything else besides a space, it's a new book.
Lines starting with spaces are short notes on what I thought
of the book. I'm not trying to write formal reviews, just reminders.
If I don't have anything in specific to say, I leave it blank or
write a word or two, like "fun" or "disappointing".
Crunching the numbers
That means it's fairly easy to pull out book titles and count them
with grep and wc. For years I just used simple aliases:
All books this year: egrep '^[^ ]' books2019 | wc -l
Just new books: egrep '^[^ -.@]' books2019 | wc -l
Just reread books: egrep '^[-.@]' books2019 | wc -l
But after I had years of accumulated data I started wanting to see
it all together, so I wrote a shell alias that I put in my .zshrc:
for f in ~/Docs/Lists/books/books[0-9](#c4); do
year=$(echo $f | sed 's/.*books//')
let allbooks=$(egrep '^[^ ]' $f | grep -v 'Book List:' | wc -l)
let rereads=$(egrep '^[-.@\*]' $f | grep -v 'Book List:'| wc -l)
printf "%4s: All: %3d New: %3d rereads: %3d\n" \
$year $allbooks $(($allbooks - $rereads)) $rereads
In case you're curious, my numbers are all over the map:
2004: All: 53 New: 44 rereads: 9
2005: All: 51 New: 36 rereads: 15
2006: All: 72 New: 59 rereads: 13
2007: All: 59 New: 49 rereads: 10
2008: All: 42 New: 33 rereads: 9
2009: All: 56 New: 47 rereads: 9
2010: All: 43 New: 27 rereads: 16
2011: All: 80 New: 55 rereads: 25
2012: All: 65 New: 58 rereads: 7
2013: All: 59 New: 54 rereads: 5
2014: All: 128 New: 121 rereads: 7
2015: All: 111 New: 103 rereads: 8
2016: All: 66 New: 62 rereads: 4
2017: All: 57 New: 56 rereads: 1
2018: All: 74 New: 71 rereads: 3
2019: All: 3 New: 3 rereads: 0
So sometimes I beat that 100-book target that the 50-50 people advocated,
other times not. I'm not worried about the overall numbers. Some years
I race through a lot of lightweight series mysteries; other years I
spend more time delving into long nonfiction books.
But I have learned quite a few interesting tidbits.
What Does it all Mean?
I expected my reread count would be quite high.
As it turns out, I don't reread nearly as much as I thought.
I have quite a few "comfort books" that I like to read over and over
again (am I still five years old?), especially when I'm tired or ill.
I sometimes feel guilty about that, like I'm wasting time when I could
be improving my mind. I tell myself that it's not entirely a
waste: by reading these favorite books over and over, perhaps I'll
absorb some of the beautiful rhythms, strong characters, or clever
plot twists, that make me love them; and that maybe some of that will
carry over into my own writing. But it feels like rationalization.
But that first year, 2004, I read 44 new books and reread 9,
including the Lord of the Rings trilogy that I hadn't read
since I was a teenager. So I don't actually "waste" that much time on
rereading. Over the years, my highest reread count was 25 in 2011,
when I reread the whole Tony Hillerman series.
Is my reread count low because I'm conscious of the record-keeping,
and therefore I reread less than I would otherwise? I don't think so.
I'm still happy to pull out a battered copy of Tea with the Black
Dragon or Bellweather or Watership Down or
The Lion when I don't feel up to launching into a new book.
Another thing I wondered:
would keeping count encourage me to read more short mysteries and fewer
weighty non-fiction tomes? I admit I am a bit more aware of book
lengths now -- oh, god, the new Stephenson is how many pages?
-- but I try not to get competitive, even with myself, about numbers,
and I don't let a quest for big numbers keep me from reading Blood
and Thunder or The Invention of Nature. (And I had that
sinking feeling about Stephenson even before I started keeping a book
list. The man can write, but he could use an editor with a firm hand.)
What counts as a book? Do I feel tempted to pile up short,
easy books to "get credit" for them, or to finish a bad book I'm not
enjoying? Sometimes a little, but mostly no. What about novellas?
What about partial reads, like skipping chapters?
I decide on a case by case basis but don't stress over it.
I do keep entries for books I start and don't finish (with spaces at
the beginning of the line so they don't show up in the count), with
notes on why I gave up on them, or where I left off if I intend to go back.
Keeping track of my reading has turned out to have other benefits.
For instance, it prevents accidental rereads.
Last year Dave checked a mystery out of the library (we read a lot of
the same books, so anything one of us reads, the other will at least
consider). I looked at it and said "That sounds awfully familiar.
Haven't we already read it?" Sure enough, it was on my list from
the previous year, and I hadn't liked it. Dave doesn't keep a book
list, so he started reading, but eventually realized that he, too, had
read it before.
And sometimes my memory of a book isn't very clear, and my notes
on what I thought of a book are useful.
Last year, on a hike, a friend and I got to talking about the efforts
to eradicate rats on southern California's Channel Islands. I said
"Oh, I read an interesting novel about that recently. Was it
Barbara Kingsolver? No, wait ... I think it was T.C. Boyle.
Interesting book, you should check it out."
When I got home, I consulted my book lists and found it in 2011:
When the Killing's Done, T.C. Boyle
A tough slog through part 1, but it gets somewhat better in part 2
(there are actually a few characters you don't hate, finally)
and some plot eventually emerges, near the end of the novel.
I sent my friend an email rescinding my recommendation. I told her the
book does cover some interesting details related to the rat eradication,
but I'd forgotten that it was a poor excuse for a novel. In the end
she decided to read it anyway, and her opinion agreed with mine.
I believe she's started keeping a book list of her own now.
On the other hand, it's also good to have a record of delightful new
discoveries. A gem from last year:
Mr. Penumbra's 24-hour bookstore, Robin Sloan
Unexpectedly good! I read this because Sloan was on the Embedded
podcast, but I didn't expect much. Turns out Sloan can write!
Had me going from the beginning. Also, the glow-in-the-dark books
on the cover were fun.
Even if I forget Sloan's name (sad, I know, but I have a poor memory
for names), when I see a new book of his I'll know to check it out.
I didn't love his second book, Sourdough, quite as much as
Mr. Penumbra, but he's still an author worth following.
[ 12:09 Jan 06, 2019
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Fri, 28 Dec 2018
The morning after Christmas we woke up to a beautiful white world,
with snow still coming down.
Shoveling is a drag, but still, the snowy landscape is so beautiful,
and still such a wonderful novelty for ex-Californians.
This morning we awoke to much the same view,
except the snow was deeper -- 8-12 inches, quite a lot for White Rock.
We also had the usual amusement of Roof Glaciers: as the mat of snow
gradually slides off the metal roof, it hangs off the edge, gradually
curling, until finally the weight is great enough that it breaks off
and falls. Definitely an amusing sight from inside, and fun from
outside too (a few years ago I made
movies of the roof glaciers).
And then, this being New Mexico, the sun came out, so even while
snowflakes continued to swirl down we got a bright sunny sparkly snow vista.
Yesterday, the snow stopped falling by afternoon, so Raspberry Pi Club
had its usual Thursday meeting. But the second storm came in hours
earlier than predicted, and driving home from Pi Club was a bit icy. I
wasn't looking forward to the drive up to PEEC and back tonight in a
heavier snowstorm for our planetarium talk; but PEEC has closed the
Nature Center today on account of snow, which means that tonight's
planetarium talk is also canceled. We'll reschedule, probably next quarter.
Happy Holidays, everyone, whether you're huddling inside watching the
snow, enjoying sunny weather, or anything in between. Stay warm,
and walk in beauty.
[ 12:28 Dec 28, 2018
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