Silicon Valley Redneck

I'm not sure where the week went...

...but somehow it got to be Sunday already.

Making preparations for visiting my parents this afternoon; my father's been doing all the cooking these past many months, and getting tired of it, so I'll be taking dinner: got a chicken in the smoker, bread dough in the works, and corn soaking in slightly salty water in preparation for grilling in the husk.

Inbemongst of that, I'm declaring a Day of Weekend to deal with stuff like installing a new showerhead and assembling the Bixler (now waiting for the glue to set on the GPS module (inside the nose, above the battery) and the aft antenna (just forward of the tail servos), and the Pitot tube is in place (poking through the nose, above the battery, next to the GPS)).  Initial testing will be with the store-boughten radio, which doesn't use any of those amenities, but they'd be hard to add once the fuselage is glued together.  Oh, and I still need to add a pair of little teeny eyes (hardware type), up top, 71mm aft of the leading edge of the wing, for balancing, and mayhap a third somewhere out toward the tail, for hanging from the ceiling.

And, last time I headed out back to tend the smoker, I found Southmoon playing with the Bridgeport.  At least she didn't have it turned on (and she'd also need to turn on the phase converter, which is probably a step too many for a youngster who doesn't even have opposable thumbs).

Rules to live by: check before you connect

And, on this occasion, it's well I did.

Got a dinky GPS module, model GP-635T, from Spark Fun, along with a matching cable (6 wires, JST SH connector on each end, fiddly 1mm pitch thing; ready-made cables are good, 'cause I don't have the correct krimpatul*).

Got a matching header designed onto a board, going by the connections in the GP-635T datasheet.

I connect one end of the cable, and pause to consider the situation.

The cable has one white wire, which I take to be a pin 1 marker, unless of course it's pin 6.  Assuming it's pin 1, it should be, according to my board, ground.  According to the GP-635T datasheet, pin 1 should be ground... only the actual ground connection on the board (according to my continuity beeper and a bit of exposed ground plane) is at the other end of the connector.  Somebody, here, is decidedly backward.

Oops.  That could have been an expensive mistake.

Did I goof up the footprint?

And so I dig out the SH datasheet, and look through the drawings, and the end where the white wire is definitely matches "Circuit No. 1" on the drawing.  So, the cable and my board agree with the connector spec.

It's the GP-635T spec that has the pins numbered wrong way which.

Ergo: hot up the soldering iron and turn that sucker around.  Also, flip the connections in the pending respin (the respin was needed anyway, and planned before I'd even gotten the first batch of boards back from fab).

Update: the connector having been duly reversed, everything (re)connected, and the serial port taken away from its default debug-console function, I'm now getting a stream of what looks like GPS data.  What's more, it's giving the location of my house; I hadn't really expected such a tiny unit to find the satellites when indoors, but it seems to have done so.

Update 2: install gpsd on the RasPi, run it, and it Just Works.  Except... running xgps for a look at the output, I see that my workbench is moving at anything up to half a mile per hour, and drifting from 100 feet above sea level to 5 feet below sea level.  So... perhaps using that dinky GPS module indoors doesn't work all that well.  Have to try it outdoors sometime soon.

* Update 3: just for giggles, I looked up the correct krimpatul (or, anyway, the cheapest officially-approved option).  Nigh unto $1100 for a hand crimper?  I have this $60 tool from Spark Fun, and, while it works great for slightly less tiny connectors, it seems to be making the conductor crimp for the SH just that little bit too flat and wide... mostly too wide... and the result doesn't quite fit into the connector body.  Maybe if I tried 28 AWG instead of 30?  But I'd need 28 AWG wire with very thin insulation.

Update 4: I got out the SR (1mm IDC) connectors again.  Supposed to be for 30 AWG stranded wire.  I have some nice 4-conductor cable with 30 AWG stranded conductors and thin insulation... but just can't get it to connect to the SR (possibly because the wire is badly tarnished).  However!  Turns out 30 AWG wire-wrap wire, punched down with a tiny jeweler's screwdriver, works nicely.  I'd much prefer stranded, but it shouldn't be seeing all that much flex, and the wire-wrap stuff is handy.  Meanwhile, on the 28 AWG front... well, I'd have to order it, in rolls of 100 feet for each color, and it's amazing how expensive basic hook-up wire has gotten, especially if you want thin (ergo, not PVC) insulation.

And furthermore: that other, 4-wire, cable I built with the SR connectors?  Meant to carry the I2C bus out to a remote sensor, a coupla feet away.  Well... it kinda-sorta worked for a while, then (perhaps because the wires got a little twistier and thus the capacitance increased just a tad) not only did the remote sensor get flakey, but one of the local sensors ceased to work at all... 'twas detected (sometimes) by i2cdetect, but wouldn't answer a read.  A reminder, kids: I2C is the Inter-IC bus, intended for connecting chips a few inches apart on a single board, and anyone running it across a backplane is either a nitwit or following a telco standard written by a nitwit.  (The main issue with regard to the common use in telco equipment is noise immunity, which I2C lacks.  The problem here looks (at a guess) to be wiring capacitance, given that there's not much noise about.  Voltage thresholds offer further opportunities for Fun, Negative Amounts Of.)

Early-morning dream

Even before the Bamboo Incident this morning, in the wee hours, shortly before my time of awakening, I was having a very peculiar dream.

I had become a character in something that resembled a mid-1960s Saturday-morning cartoon, only with good-quality CGI, and maybe it was part live-action (I remain unclear on whether the human characters were actors on camera or CGI constructs).

Anyway, the villain had some kids trussed up and floating atop some sort of goop (lumpy tomato paste?) loaded in an open-top box (truck?  Rail car?) of the sort used to transport, e.g., underripe tomatoes.

Whatever the evil plan was, it had just been foiled, and everyone was safe, when (characteristically, it seems) just too late to do anything useful, SuperTurtle, the Kryptonian chelonian, was on his way from outer space at half the speed of light!

Those of us with a vague knowledge of physics did not find this reassuring, and I was trying to do the math when ST arrived, splat!, head-down in the goop.

Once awake, but not awake enough to refresh my memory on relativistic effects, I did a naïve calculation of the kinetic energy of a ~ 75kg SuperTurtle arriving at 0.5c: about 200 megatons?  Not exactly a comical splat.  Thank Warner for cartoon physics!

(OK, so it's not exactly "Selige Morgentraum-Deutweise".)

Such a Monday morning!

The kittens are ever so awake.

Southmoon has been, characteristically, climbing.

Shortly after I woke up, she climbed the shelves by the dining table, reaching the itty-bitty shelf at the top where lives Joy's bamboo-in-a-jar... which, fortunately, I hadn't gotten around to watering recently.  Crash!  Splash!

Then climbing hither and yon around my office while I'm trying to read my morning internets.

Huckleberry and even Top Hat have also been getting into everything that doesn't require quite so much climbing.

Monkeys!

It remains to be seen what the day will bring....

Saturday

Up earlyish (though later than weekday normal), and off to the Electronics Flea Market.  'Twas rather disappointing, compared to years past; there was some cool vintage stuff, and some oldish test equipment that would have been good for equipping a new lab on a shoestring budget, had I not a full set of basic equipment already, but... just not a lot of people, nor a lot of really cool stuff.  Met with someone I'd encountered at Maker Faire, and had a lengthy discussion of nifty ideas, some of which may come to fruition in the fullness of time.

Then off to AeroMicro for a couple of odds & ends.  (Really, it would have been less trouble just to buy my first electric RC plane there: local, with staff who are Into The Hobby and know their stuff, and it wouldn't have been that much more expensive than buying on-line.)

Then!  Put in an appearance at the TechShop open house.  People showing off their Cool Stuff (some of it very cool indeed).  Rather a smaller event than I'd expected... but there'd been on in SJ last week, and SF the week before that, so perhaps everyone was TechShoppEd out.

One the way home, swing by TAP Plastics for some Stuff for a project I'll maybe describe later.

Then home, and I figger I might as well unBix the boxler unbox the Bixler and have a little closer look.

The assembly instructions aren't nearly worthy of the name.  If you're putting together the "Almost Ready to Fly" version, you'd better have pretty good mechanical aptitude and a fair idea of how things are supposed to go.

Fuselage disassemblement to allow motor installation took a bit of figgerin'.  I had to cut through the gummy glue holding the top fairing over the motor compartment in place.

Having more or less figured out how things go together, I proceeded to install the 3.5mm bullet connectors on the speed controller, clamp the motor mount in a vise, connect ESC to radio and to a bench power supply set for mostly-charged 3S LiPo, and verified that (1) the radio-ESC-motor path works; and (2) matching colors of the motor leads turns the prop the right way.

Oh, radio.  Servo connectors.  Orientation of connectors is not clearly marked, and the manual (once found and downloaded) is no help.  What to do?  I had a couple of old-ish Futaba micro servos sitting on the bench; they have physically keyed connectors.  Do they plug one way and not the other?  Yes!

...Wait.  Is that actually right?  I should be able to check this with a continuity beeper: the ground and power rows should connect straight across, while the signal row should have all separate pins.

Uh-huh.

The way the Futaba servos can be plugged into the HobbyKing radio is exactly and perfectly backward.

I assume the servos that came with the plane are not physically polarized, so the problem there will be merely one of ambiguity and not positive wrongness.  Still, 'twould be nice if these things were standardized.

And, while I'm at it: yes, the cavity within the fuselage of a Bixler is juuuust wide enough to accommodate a Raspberry Pi.  Removing the composite-video connector might be helpful.

Anyway: I'll probably get the Bixler actually put together in the coming week, and maybe even find an opportunity to put it in the air, using the store-boughten radio.  (And maybe there are parts of the assembly I want to do with gummy glue rather than really permanent stuff...?)

Nearer-term tinkering time, such as it is, should really go to checking out the bits of the planned flight-control system.  Maybe tomorrow afternoon....

Update: found actual Bixler (and similar) assembly instructions here.  Step 1: "Dispose of the instruction manual (4)."  This seems to be for a slightly different version, but should prove useful.  'Twould be even better if the manufacturer, having the CAD files and all, had generated some nice diagrams showing what goes where and how it's meant to be affixed, but user-group docs are still helpful.

(And I have the feeling I'll be annoyed by the lack of tie-downs, bulkheads, and suchlike.  I have this quaint notion that everything aboard a flyin' machine should be firmly anchored to avoid shifting around and affecting balance... and things like inertial and magnetic instruments, in particular, should have a permanent fixed relation to the airframe.  Oh, well: glue.  And - d'oh! - velcro (not included (update: hey, the small-parts bag has some velcro bits in it)), for the parts that need to be tethered but not with precise orientation.)

Further afterthought: I reversibly affixed the canopy to the cockpit insert with common pins from the Tackle-Box of Sewing Stuff.  This could set a precedent for locating inner items such as nav platforms; perhaps I'll throw together a location jig (could be made of heavy paper) for getting holes in well-defined locations on the sides of the fuselage, and use pins (or some approximation) for holding stuff in.

Heavy stuff probably wants better mounting than that, though, lest a rough landing cause the pins to slice through the foam.

I probably want to mount the Pitot tube before gluing the halves of the fuselage together, just to keep things easy.  Hmm, and make some allowance for placing the magnetometer / air-temperature probe, which would also be much more difficult after assembly.

Dang.

Had a kinda cool idea for a kit (which I'm still toying with).

Basic concept fits handily in an ATmega328, and the builder/owner/user could hack the firmware using the Arduino toolchain.

But!  A super-extra-cool feature requires a second UART.

A second UART is available on the ATmega324... but the xx4 series isn't officially supported by Arduino, so not a good choice for a kit.  (Apparently there's some unofficial way of using xx4 parts with Arduino, but it involves some tinkering with the toolchain's configuration.)

That leaves the ATmega1280, which is supported by Arduino, but... it's a 100-lead package, so a big footprint and no through-hole option.  Also, it's rather pricey, though the price comes down to a little over $9 in hundreds.

Hmph.  Well... if I go with ol' familiar '328, I can add a serial port (with RS-485 half-duplex support) via I2C and, e.g., a $2-in-hundreds SC16IS750IBS.

Which is plausible, I suppose, but I'd much rather use the '324.  Which I can program myself, no problem (not really speaking Arduino and Wiring much anyway, but being pretty good at AVR and C), but part of the idea was to provide a platform the user could tinker with easily.

There, I fixed it!

But, alas, omitted to photograph the result before plumbing it up.

The day having become a total washout from the point of view of making progress on the Real Work that had been on the agenda, I used a chunk of the afternoon to deal with a garden crisis.

Rather a lot of my plants were Not Doing Well At All.  The reason for this had become apparent on Sunday afternoon: sometime in the last month, one of the valves in the automated watering system had mostly failed, and was letting only a trickle of water through.

There were three valves.  One was not in use... unfortunately, that was because it had failed last year.

So, time to replace a valve or two.  3/4" pipe thread both ends, anti-siphon type, goes up and across and down.  Easy-peasy!

Or not.  See, the valves that are conveniently available this year have an inch or two more across between the up and the down, and can't be installed on my old manifold: the stations are too close together, and the new valve bangs against its neighbor long before it's screwed in.

Also, the wooden frame that I made to attach the manifold to the side of the house, all those many years ago, has pretty well disintegrated, so that needs attention too.

And so, off to OSH for a set of three current-model valves, and several feet of PVC pipe, and tees and elbows and adapters and...

...And, once the pipe is cut, the bits glued together, a couple of parts done over because I lost sight of my Vision, and a trip back to OSH for a couple of end caps after realizing that my original Vision was going to be nigh-impossible to finish assembling...

...I have a weird PVC sculpture that's free-standing, supports the three valves across the top, has the inlet hose coming in from the left and a capped 3/4" pipe thread outlet on the right (just in case), and gets my automated watering back up to full capacity.

I'm toying with the idea of making a PVC pipe sculpture to run along the roof, carrying a line of sprinkler heads, for giving the roof a quick spray on hot afternoons.  Wouldn't have an automated valve, though, unless I expanded the system and replaced the 6-channel timer with maybe a homebrew many-channel sprinkler controller with perhaps 802.15.4 or Bluetooth to let the computer talk to it.

Hmmm.

Busy, busy...

...and, all around, rather a high-stress week, and more to come.

Ill friend / business associate went into the hospital Thursday, not yet for treatment of the serious problem found a week earlier (he was still waiting for a call back from the preferred hospital for that sort of thing) but to investigate why a 2-weeks-earlier sports injury was still so painful, and...

Well, he's in the hospital for what may be Yet A Third Thing (or could be related to either or both of the previously-known problems) at least until Monday.

I gotta spend a chunk of this weekend (as I did a chunk of yesterday) doing what I can to get the big, year-delayed project ready for delivery, so when he's back out of the hospital he can wrap things up and deliver that beast.  And we can get paid for it, after all this time & effort.

And there's a new project that's been in "wait to hurry up" mode for a couple of months now, that may be coming to life, like, Right Now.

Meanwhile, I was getting a chunk of the bread-and-butter work done, both to suit the client's (much delayed, for various reasons) schedule and to get the hours on the May invoice, because Cash Flow.

In other news:

I found time to visit a very interesting little startup company that a friend had stumbled across the previous week.  They're doing totally cool stuff, and there may be opportunities for business and general cooperation.

I also spent a couple of hours getting the second iteration of the Geiger counter (a non-USB model, with some improvements on the original thrown-together-in-a-couple-of-hours design) assembled (hot-air soldering a tiny SMT-both-sides board is a pain), programmed, and tested.  I'm now putting all three of the ATmega88's timers to good use, and it goes click-click (if one connects a speaker) as well as reporting results via UART.

And, I ordered a Bixler (cheap, medium-sized, plastic-foam, radio-controlled trainer airplane) to use as a testbed for a couple of my other projects in the works.  The order still shows as "processing" rather than "delivered", but it's not like I'll have the time to do anything with it before the middle of June anyway.  Though this is really a business expense, I think it'll be on the books as "personal", 'cause I don't feel like trying to explain it to the IRS.

Professionalism

When writing technical process documentation, and doing a walk-through to ensure that the steps in the documented process match the actual process in every important detail...

...It is nonetheless considered good form to omit steps along the lines of "Remove kitten from modulator subchassis."

Yipe.

Just when I thought life might be stable for a little while....

A friend and business associate has just been diagnosed with a serious illness, and is likely to be more or less incapacitated for TBD beginning TBD.  Yes, there are serious blanks to be filled in next week, pending a more detailed diagnosis.

This leads to a flurry of activity to get as much work as possible wrapped up and delivered in the next TBD, and to make arrangements for keeping the business on track for the TBD following that, and to make contingency plans, and....

And I'm involved in TBD% of this, so things will be Considerably More Hectic Than Previously Anticipated.

Meanwhile, I'd picked up several business leads in the past week, and need to be following up on them.  Some might turn into actual business almost immediately, while others are clearly at least a few months off, but still need cultivating.

Posting may be light.  Or heavy, depending.