OpenMarine and Signal-K

 I heard about these less than a week ago.

• https://openmarine.net/openplotter
• https://github.com/openplotter/pypilot
• https://signalk.org/installation.html

This is very interesting. Very interesting.

I have a partially complete IoT anchor alarm.

The idea of leveraging the boat's other devices through a Signal-K interface is appealing.

The problem is, I don't want the power draw.

I think I want to continue on the path of a small, thrifty, stand-alone device that can be used when the rest of the boat's systems are mostly shut down.

However. Seeing these projects causes me to rethink my use of Arduino and C++. While the Arduino is the thriftiest possible device -- the power consumption is negligible -- I think that a small upgrade to a Python-based device might make the software a tiny bit simpler. 

An Arduino Uno, specifically, is just barely capable of the UX I was hoping to build. The two-line LCD with a "mark" push-button, an "anchor circle" knob, and a "display page" button is right at the limit; I'm using analog inputs instead of digital for the buttons.

A Raspberry Pi can support more sophisticated displays, at some cost in power consumption. An e-ink display might be a better choice than the two-line LCD because -- well -- anchoring details change slowly.  Once you've drifted too far (or have a consistent COG away from the marked point with a steadily growing distance) then the alarm sounds and the display is more-or-less irrelevant. You're going to get up, and eyeball the situation to see what's going on. Wether or not the display updates doesn't matter much. 

We haven't drifted very often, so I don't have too much data.

1. Once we slid to a new position. It was a stormy, blowy day. We eased out more scope. And we never moved again. We stood on deck, taking visual bearings. An e-ink display of the details wasn't what we depended on.
2. We used to rely on an iPhone app to monitor our position. (We've switched to using SafeAnchor, we used to use an older app, no longer available.) We were moving slowly, but steadily. It was during a hurricane, we weren't surprised. We started the engine, raised the anchor and motored to a new place to reset. Again, we weren't using the display on the phone, we were looking at Pungo creek.
3. And once we were not on the boat when she moved. That would have been awkward for our neighbors. So. We'd need to have a "reset the anchor alarm" switch in the cockpit. This would mark a new position. Fatty Goodlander's advice is to leave a big sign with a string showing them where it is.

A full 1.0 knot of speed is 1.7 feet per second. We often have 50 feet of line, meaning any movement under 100' is likely ordinary boat motion. That means 30 seconds until we're suspicious of a problem, and a full minute before we must sound the alarm. (In the middle, a constant COG and increasing distance is a leading indicator of trouble; alarm chirps might be helpful.)

As intermediate data gathering format, the Signal-K data stream is appealing. It steps away from the NMEA GPS talker messages. It's heavy-going for an Arduino Uno. But. Might work out well on something a little bigger.

Another shiny new MacBook pro

See https://slott-softwarearchitect.blogspot.com/2014/03/shiny-new-macbook-pro.html

At the time (2014), the 8Gb machine was way more than adequate for all my needs as a writer.

Enter bloat.

Mac OS Catalina has essentially filled this machine to the breaking point. Six short years is the lifespan. Things (generally) work, but it now crashes frequently. Sometimes, streaming TV won't play properly. I've tried a large number of remedies (reboot WiFi, reboot computer, reset Bluetooth) and it glitches too offten to be comfortable.

(Rumors suggest the crashes seem to be associated with going to sleep. The machine crashes when it's idle. I come back to it and find it has restarted, and needs to restart my apps. It's not horrible. But it's an indication of a deeper problem. And it's time.)

It works. But. I've spent too many years waiting for slow computers and slow networks. An hour a day (cumulative) for 300 days a year for 40 years means I've spent 1.3 years of my life waiting for a computer to do something.

I’m reluctantly replacing my kind-of-working "Late 2013" vintage machine with a new 13” MacBook Pro. At least 16Gb RAM. At least a terabyte of storage. Hopefully, things will not be "glitchy" and I won't have constant crashes.

I’ve gotten used to having an 27" Thunderbolt Display, and a USB Querkywriter keyboard, and two USB disks doing backups. That's a lot of stuff plugged in all the time. Also. I really need a slot for SD cards (the boat uses micro SD cards, as does the old GoPro camera.). So. A fancy USB-C hub will be essential, I think.

The question is 2 ports (power and hub) or 4 ports (power, hub, and two other things)?  I suspect I can live with 2 ports.  4 ports ships immediately.

I have several use cases:

• Writing Python books (e.g. Modern Python Cookbook 2e, https://www.packtpub.com/product/modern-python-cookbook-second-edition/9781800207455)
• Writing fiction. (Still editing second drafts, don’t hold your breath)
• Creating a MicroPython (or Arduino) device to track my boat’s position and act as an alarm if the anchor drags
• Boating (in a vague, general way)

Writing books actually requires some computing power. But. Not *too* much power. The general reader doesn’t always have a huge computer. If my examples require more computing power than my readers have access to, that’s a problem. The advantage of having a smallish computer is I’m not overstepping what’s available to my readers. This is a handy way to take a tax deduction to pay for this extravagance.

Writing fiction requires a small machine. Scrivener works on an iPad Pro. I’m good with almost anything. Even an iPhone can be used for writing and editing fiction. It’s hard, of course, with a tiny screen. But not impossible. And. I'm trying to learn the craft, so tools aren't as important as understanding character arc.

Creating MicroPython-based devices is a bit confusing right now. A lot of the development environments depend on a reliable USB connectivity to the Arduino or Circuit Playground Express board. I worry about the (potential) complexity of introducing a USB hub into the mix.  I suspect I only need to replace some of my USB cables; the Arduino boards all seem to use a bulky USB type B. The CPX use USB type Micro B. (I thinks one can be replaced with a USB C to USB B “printer cable”, the other is a USB microB to C adapter. Or, maybe a USB C to USB A adapter can be used with my vast collection of legacy cables. Don't know.)

Boating involves connecting external devices like the GPS antenna to the laptop and tracking position or planning routes. This is a Bluetooth thing, generally. 

It does require considerable power for the laptop; the 60W power brick becomes a constraint. The boat have an inverter and can handle the load gracefully. A computer is a dedicated 5A draw, though; twice what the fridge pulls (and the fridge runs infrequently.) We have 225Ah available. The computer could be as bad as 120Ah if it was left on for 24 hours during an overnight passage.

The good news is that the use cases are more-or-less exclusive. The boating use case is rare. We have more thrifty navigation systems permanently installed on the boat. Many folks are using CPX and Arduino’s with MacBook Pro’s, so I shouldn’t worry too much, just buy new cables.

The best part?

Since I use Time Machine, the new machine recovers from the Time Machine backups. It has to be left to run overnight, but. Boom. Done.

(On the to-do list -- encrypt the backup volumes. Ugh. But. Necessary.)

Christmas Ornament

See https://github.com/slott56/cpx-xmas-ornament

You'll need a Circuit Playground Express https://www.adafruit.com/product/3333

Install the code. Enjoy the noise and blinky lights.

The MML translation isn't as complete as you might like. The upper/lower case for the various commands isn't handled quite as cleanly as it could be. AFAIK, case shouldn't matter, but I omitted any lower() functions, making the  MML parser case sensitive. It only mattered for one of the four songs, and it was easier to edit the song.

The processing leaves a great deal of "clickiness" in the start_tone() processing. I think I know how to address it.

There are barely 96 or so different tones available in MML compositions. It might be possible to generate the wave shapes in advance to have a smoother music experience.

One could image having an off-line translator to transform the MML text into a sequence of bytes with note number and duration. This would slightly compress the song, but would speed up processing by eliminating the overhead of parsing.

Additionally, having 96 wave tables could speed up tone production. The tiny bit of time to recompute the sine wave at a given frequency would be eliminated. But. Memory is limited.

Circuit Python on the Gemma M0 -- The Red Ranger Beacon

PyCon 2018 Swag included a Gemma m0. (https://www.adafruit.com/product/3501)

PyCon 2019 Swag included a Circuit Playground Express. See https://learn.adafruit.com/adafruit-circuit-playground-express/circuitpython-quickstart.

Both of these are (to me) amazing. They mount as USB devices; there’s a code.py file that’s automatically run when the board restarts.

The Gemma has fairly few pins and does some real simple things.  The CPX has a bunch of pins and ton of hardware on the board. Buttons, Switches, LED’s, motion sensor, temperature, brightness... I’ve lost count.

Step 1 -- Get Organized

Create a proper project directory on your local machine. Yes, you can hack the code.py file immediately, but you should consider making a backup before you start making changes.

Few things are more frustrating than making a mistake and being unable to restore the original functionality as a check to be sure things are still working.

Also. At some point, you'll want to upgrade the OS on the chip. This will require you to have a bootable image. The process isn't complex, but it does require some care. See https://learn.adafruit.com/welcome-to-circuitpython/installing-circuitpython#download-the-latest-version-3-4 for downloading a new OS.

So. Step 1a. Create a local folder for your projects. Within that folder, create a folder for each project. Put the relevant code.py into the sub-folder. Like this

gemma
 ┣━━ baseline
 ┃   ┗━━ code.py
 ┣━━ my-first-project
 ┃   ┗━━ code.py
 ┣━━ another-project
 ┃   ┗━━ code.py
 ┗━━ os-upgrade
     ┗━━ other files...

See https://learn.adafruit.com/adafruit-gemma-m0/troubleshooting for additional help if you have a Windows PC.

Step 2 -- Start Small

Tweak a few things in the supplied code.py if you're new to IoT stuff.

A lot of folks like the Mu editor for this. https://codewith.mu.

I like using BBEdit. https://www.barebones.com/products/bbedit/.  To make this work I *also* need to have

• a terminal window open so I can use the Mac OS screen application, and
• a finder window open to copy the code.py from my PC to the Gemma M0.

This is a lot of busy screen real-estate with three separate apps open. It's not for everyone. I like it because there's little hand-holding. You may prefer Mu.

It's important to go through the edit/download/play cycle many times to be sure you're clear on what code's on your PC and what code's on your board.

It's even more important to see how you're forced to debug syntax errors using the screen app until you invent a suitable mock library for off-line unit testing.

Step 3 -- Plan Carefully

The version of Python is remarkably complete.

However.

It's also a very small processor, with very few pins, so you can't do anything super elaborate.  You can, however, do quite a bit.

See Nina Zakharenko - Keynote - PyCon 2019 for some inspiration

Step 4 -- Check This Out

https://github.com/slott56/gemma-boat-beacon

Many thanks to @nnja for showing us some elegant, inspirational ideas.