understanding blockchain

Bitcoin is a relatively new phenomenon, getting its start only nine years ago. Since that time, it is now enjoys a market cap of about US$150B at the time of this post. That’s an admittedly-large sum of money for something that’s completely digital and you can’t hold in your hand at the end of the day. I guess it shares the same status then with stocks, bonds, mutual funds and other trading instruments that are a bit ethereal, if you ask me. That said, though, it has come a long way since its inception and there are a thousand or so copycats in one form or another. And yet, does the average person know anything about the underlying code and how it’s implemented?

I thought I’d put together a collection of terms to shed some light on the underlying technology to make it easier to understand.

Node

A node is a single identifiable unit in a variety of storage systems. It often includes a unique ID of some kind to make it distinguishable from its neighboring data. A node could be as simple as the following:

1,This is the data part
2,And this is more data

Linked List

A list is usually something like a comma-separated list of data. A linked list is one in which each new bit of data points back to the previous one in some way. And there are even varieties of this in which the new data points backward and the existing data points forward as well. Here is another example which includes backward-facing pointers:

{ID=1,Data="This is the data part",Previous=0},
{ID=2,Data="And this is more data",Previous=1}

Hash

In the cryptographic world, a hash is usually a large number which was generated from a collection of data. You should assume that the same collection of data as seen later would continue to produce the exact same hash as an output. Furthermore, no other collection of data should produce the same hash. Here’s another example with short versions of hashes included:

{ID=1,Data="This is the data part",Hash="5a285ab1945",PrevHash="00000000000",PrevID=0},
{ID=2,Data="And this is more data",Hash="b6f7f023f02",PrevHash="5a285ab1945",PrevID=1}

This storing-of-the-previous-hash-value in each record is important to prevent any tampering by someone else.

Digital Wallet

Now that you know what a hash is, it’s not too difficult to imagine that a digital wallet (financial account) is represented by one of these as well.

Transaction Ledger

A financial ledger in the form of two paper-based books is something that accountants used to fill out to maintain a company’s finances. A ledger is a history of all the adding and subtracting for the different accounts.

If the data part in our examples above actually represent those +/- activities and correctly identify a pair of financial accounts, then this might be an excellent way of publicly keeping a record of how much different accounts hold in some form of currency.

Block Number

Now that you know what a hash is, that unique identifier/number for each node or block of data is yet another hash number.

Merkle Tree

Since a block can store not one but several transactions in it, the method of storing the data is important. A merkle tree is a way of storing data with individual hashes on each branch plus combined hashes as well at the point of intersection of those branches.

So as we described above, a block can have multiple transactions stored in it. Each individual transaction would include a hash and the accumulation of transactions also gets a combined hash for the sake of safety.

Miners

A Bitcoin miner is a computer whose job it is to create and add blocks to this public ledger. More accurately, though, a miner is usually a single graphics card in a computer which has been setup to mine coins. It requires a fair bit of processing power to do what should be a simple task.

Nonce

A nonce is usually an integer and in our context, it means a special integer which—when added to the contents of a block—produces a hash which begins with four zeroes. As you might have guessed, it requires a bit of work to produce a working hash for a block of transactions and this is the “work” which Bitcoin miners do, for example.

When the correct nonce is guessed and a valid hash produced, it is published along with the block. If this is unique work and was done first then the miner might be rewarded with an amount of digital coin.

Blockchain

A blockchain, then, is a public, distributed ledger of groups of transactions stored in blocks. Each block has been assigned a hash which was programmatically difficult to produce. Each block includes information about the previous block in the chain, making it nearly impossible to alter after-the-fact.

A blockchain allows a digital wallet (as identified by a hash) to have a balance which is the collection of +/- transactions into that account.

 

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add comments to a gcode file

I’ve just written a new command-line tool (CLI), this time in NodeJS/JavaScript but as usual, it’s open-source. The program will create a new version of your 3D printer’s GCODE file, adding comments along the way which describe what each command does.

repository

I would suggest that it’s best to install it somewhere in your path and then you should be able to just invoke it easily in your working directory where the GCODE file(s) live:

 

$ gcode-comments file.gcode

;FLAVOR:RepRap
;TIME:11265
;Generated with Cura_SteamEngine 2.3.1
M104 S205            ; Set extruder temperature
M109 S205            ; Set extruder temperature and wait (blocking)
;LAYER_COUNT:28
;LAYER:0
M107                 ; Turn off fan
M205 X10             ; Adjust jerk speed
G1 F2400 E-1         ; Move and/or extrude to the indicated point
...

Input:  file.gcode
Output: file_commented.gcode

hello

Since I’m now an instructor, I thought I would create a repository which demonstrates  code for the many languages out there which could produce a command line tool/interface (CLI).

HelloCommandLine

Currently, there are nine languages represented but I may add more later. Note that everything here is decidedly OSX-specific. Each subsection includes the instructions for running and/or compiling each, noting that some are compiled languages and some are not.

talking at the speed of lightning

I give so-called “lightning talks” at San Diego JS, a four-times-per-month local group on Meetup.com. Each talk only lasts five minutes so there’s time for several speakers within the span of a single event.

The venue is typically packed. Here’s a photograph of a typical turnout—there were about 120 attendees this month alone.

I suppose you can communicate a lot in a mere five minutes. It is a bit challenging to try to distill down all the things you need to say into this timeframe. There’s really no room for story-telling, just tell the straight facts and details as you race through your slides and screenshots and nothing more. At best, you can hope that someone will ask a relevant question which may allow you to go into some detail you’d earlier hoped to have included.

Challenges

Many of my projects involve more than one computer. Unfortunately, the security settings on most wi-fi routers at venues like this don’t want you to connect from one computer to the next. The router would actively prevent your demo from working. So I’ve learned to bring along my own networking, which is a hassle. This is especially difficult with IoT projects, for what it’s worth.

Another challenge is related to power. It seems like each of the speakers needs to setup prior to the event and so they all want to bring along their power adapters and plug in. This means that the venue would need to accommodate all those brick-style adapters and they usually forget this.

And I suppose, a recurring problem is that of screen resolution compromises that you have to put up with. You will have formatted all your screens for one resolution while creating your content, only to find that you’re now presenting in a smaller resolution. This then threatens to clip off content or the font size is now too small to be seen by those near the back.

Regardless, it’s a rewarding experience and I hope to give more talks in the months to come. I would encourage others to do the same. It’s a great opportunity to give back to the community of like-minded coders.

mobile app for the robo

I’ve written a new mobile app for the Robo C2 and Robo R2 set of printers by Robo 3D, a local San Diego—based company.

Robo-Home

Details

It’s written in the Adobe PhoneGap (Cordova) platform with Framework7 for the styling and scaffolding. It communicates to the underlying OctoPrint interface inside the printer itself. Rather than building several smartphone apps and being subject to the recurring annual developer fees by Apple/Google/Microsoft, I intend to serve it up in a more economical way: embed another single-board computer inside the printer.

PiZero

This will fit nicely on a $10 Raspberry Pi Zero W computer, as shown. It’s then powered by the USB 5V supply inside the printer and would be powered on every cycle. I’d then use my iPhone’s or iPad’s browser to simply connect to the app.

Progress

The app is fully-functional for the Robo C2 printer and sports a slick-looking interface.

Repository

Screenshots

And here are some obligatory screenshots of the app.

Robo-LeftPanel

Robo-Motors

Robo-Files

 

keeping your pi cool

An average computer’s operating system maintains some logistics about the cpu, like its input voltage, temperature and the like. The Raspberry Pi single board computer is no exception and will even scale back its speed if it determines that its internal temperature is getting too high. That’s a good thing but another approach is to proactively cool the cpu with a fan when it’s approaching that threshhold.

pi-temp.png

Since I’m creating a cube-like chassis to hold four of these Raspberry Pi 3 computers, I’ll soon need this functionality. So I’ve just created a new repository with JavaScript code to return the cpu’s temperature in fahrenheit/celsius as a string or a number. One could then programmatically turn on/off a fan using the GPIO pins using this information.

Here’s that repository:  raspi-temp

to type or not to type…

that is the question.  Rather than a Shakespeare reference, I’m here referring to a term in software development which determines how a language deals with variables, for example.

Define: type

When you create a variable in a computer language, it’s usually something like this:

var someVarName = 1;

In a case like this, we might infer that someVarName stores a number (an integer).  We might say that the someVarName‘s type is integer.  Using a pet-ownership metaphor, it’s like purchasing a dog house first (“someVarName”) and then next buying a dog to put into it (“1”).  You wouldn’t buy a fish bowl to store a dog… although this seems to work out great if you own a cat.  JavaScript, e.g., is like this picture:  it doesn’t seemingly care if you want to store a cat in a fish bowl.

cat-in-a-bowl

Two Schools of Thought

There are two camps out there:  those who like languages which force the variable type and those who don’t.

A statically-typed language usually involves a step in which your code is converted into something else (compiling) and any type-related issues must be fixed before a program can be created.

A dynamically-typed language is run “as is” and the code is evaluated at the moment of truth—determinations about the type of a variable are made at this time.  If there is a type-related issue, your end-user could be the first person to see the error.

Statically-Typed Dynamically-Typed
Java JavaScript
C++ Python
C# PHP
C Objective-C

The Pendulum Swings

Over the past three decades, the popularity of either approach has waxed and waned.  It’s safe to suggest for the moment that the less-strict languages are gaining rapidly in popularity over their stricter counterparts.

most-popular

We have the world of open source to thank for the popularity and speed of development we’re currently seeing in these dynamically-typed languages like JavaScript and Python.

Seeing the Future

Honestly, though, there are too many people in that strict-is-better camp and their influence is felt within software development companies.  If I were to guess at the future of JavaScript, I’d probably have to say that TypeScript and Flow will gain in popularity as larger development teams look to lower the number of bugs in their code.

I don’t know, though.  Maybe it’s time that we just relax and let the cat hang out in the fish bowl.

 

blinking the raspi’s built-in LED

I’ve just added a repository of some JavaScript code to take over and exercise the built-in activity LED on a Raspberry Pi Zero W (and presumably other models). It’s called gpiozero-toggle-led and it’s a pretty simple interface with installation instructions and some sample code. It works with the underlying js-gpiozero JavaScript port of the popular original Python code. This would be an excellent way of simply demonstrating GPIO without any additional wiring, components, breadboards, extra power supplies or electrical knowledge (like finding a 330-ohm resistor using its color bands).

zero-wireless

Note that the “zero” in the title of the repository and in js-gpiozero does not refer to the Raspberry Pi Zero but to the original gpiozero Python library.

This should remove some of the guess work when attempting to use the relatively-new library since their documentation examples at the moment are taking a back seat to their code port from the more-extensive Python offering.

This approach can easily be modified to instead exercise external LEDs (as soldered or otherwise attached to the header pin locations seen below).  Note that you’ll use “BCM numbering” for APIs such as this one. For external LEDs, you would need to connect it inline with a resistor from a selected pin to one of the grounds for this to work with correct orientation of the LED’s anode/cathode, of course.

raspberry-pi-pinout

If you’re trying to use this with a Raspberry Pi of a different model, you’ll likely want to adjust the JavaScript slightly as seen below.

/routes/index.js:

// Existing code, for a Raspberry Pi Zero
var ledActivity = new LED(47, false);
// For Raspberry Pi 3, for example
var ledActivity = new LED(47);

And that’s it. Since the Raspberry Pi Zero assumes an opposite value for true/false than the bigger models, it’s necessary to configure this in the device constructor to make things work as expected. Since BCM pin 47 is the activity light on the board itself, this will allow you to control it.

o please, gentlemen, a little bluer…

Today’s inventiveness involves a new teaching method for music, a synesthetic approach to colorizing musical notes. The title’s quote comes from Franz Liszt, a 19th-century composer who was a synesthete—he saw music in full color.

Although western doctors probably think of synesthesia as a malady, I would suggest that it is a product of beneficial neuroplasticity. The brain has cross-wired itself across the senses to allow for better recognition and appreciation of something. There’s a long list of famous musicians and composers who wrote of this personal condition and in each case it helped them to succeed.

vexflow-syn

In order to promote this cross-wiring in young musical students, I’ve created a repository to colorize musical notes in client-side JavaScript. I’ve developed an organized method for this and have described the process there.

Compatibility

Given that the client-side JavaScript approach requires the newer HTML5 canvas features, this will work on newer browsers (and seems to be working in IE11 if you “allow blocked content”).

Musical Talent

I have always had a fondness and an early aptitude for music. In fact, I had such a brilliant audible memory and an ability to play anything I’d just heard, that I used this as a crutch when confronted with the task of learning to read musical notation. I didn’t actually have to read the notation in band since the sound of the music was in my head. So although I was a slow reader with respect to notation, nobody actually could tell.

My earliest formal training was for the saxophone, noting of course that you only play a single note at a time. Unfortunately, this led to my later difficulties in learning to play the piano in my thirties. Piano chords on a stave? To me, this just seemed like jumbles of notes piled on top of each other. I had no easy way of interpreting what I was seeing.

After many weeks of painstakingly trying to decypher these heiroglyphics, if you will, I began to have a small breakthrough. My brain started to recognize some patterns. Due to some unfortunate timing, I had to stop all this training and abruptly move and had to sell the piano. It would be another decade until I’d bought another piano to re-learn piano notation.

Attacking the learning of chords-in-notation anew, I realize that colorizing the notes would be a benefit to me.  All C notes are red.  All E notes are yellow.  C-E-G are primary colors (C-maj).  The Eb in the middle of the C-min chord is more orange than the original yellow. A synesthetic approach to musical notation is a wonderful adaptation to a centuries-old teaching methodology I’d suggest, at least in my own case.

too much fun

My two packages arrived today at the post office so I just hauled in all the loot from this earlier post in which I’ve purchased some new toys.

Raspberry Pi Zero W

The photos from their website don’t really describe how truly small this computer is now. They’ve somehow managed to stack the RAM on top of the microprocessor to save space. As I’ve apparently ordered the wrong video adapter cable, I’ve got a trip over to Best Buy Frye’s Electronics this evening so that I can sort that one out. I need a female HDMI to DVI, in other words. Otherwise, I’m still pretty stoked. Since there’s only one micro-USB I think I’ll temporarily need a small USB hub while I’m at it.

PiZero

NeoPixel Ring

This arrived as well, all four of the segments but it was lost on me that I’ll need to solder each of them together. Fortunately, I have a soldering iron here somewhere. :looks around: I’m certain of it.

COZIR CO2 Sensor with RH/Temp

And in the other relatively BIG package is the relatively small sensor package. No wonder they charged me $21.88 to ship this to me. Seriously, it weighs about an ounce.

And it looks like I’ll need a 2×5 jumper to attach this over to the Raspi, with a solder-able header for that, too.

Update 1

Alright, I’m back from Frye’s with a handful of stuff and I’m back in business. The video adapter allows me to see what’s coming out of the Raspberry Pi Zero W and the micro-USB hub allows me to hook up a keyboard and mouse to talk to it locally. A first install with the Raspbian Jessie Lite image resulted in a terminal-only configuration (I must have been in a hurry and didn’t read the differences on their page) so a second install of Raspbian Jessie with Pixel was just what it wanted: a full desktop experience.  If I get some time this weekend I’ll try to have it talk to either the sensor or the light ring.

Update 2

I just managed to solder together the NeoPixel ring. Due to the size of the electrical pads on the ends of these, I’d suggest that this falls into the catagory of advanced soldering and not to be taken on by the average person.

NeoPixel
These are not my lovely hands.

Additionally, I’d say that this feels a bit fragile in the area of the soldering joints between each quarter-circle. I’m going to suggest that anyone who incorporates one of these into their project needs to seriously think about ways of making this more stable/reliable since the soldering joints between them are tenuously-small.  (Imagine three distinct electrical connections across the tiny width of this thing.)

What I also found is that there isn’t anywhere to clamp a hemostat for soldering these jumpers since the LEDs run all the way to the end where the connections should go.

I did add an inline resistor as Adafruit suggested to lower the input voltage or perhaps to lower start-up voltage spikes.

I managed to re-purpose a nice external 5V switching power supply that should drive all the LEDs nicely. It was left over from the supercomputer project when I swapped in a USB-based charger instead for that. Amazingly, Adafruit suggests that those 60 LEDs need a whopping 3.6A of power to drive them. I’m guessing that reality is more like 1A but I’ll play this safe. Per Adafruit’s suggestion I included a 1000 µF electrolytic capacitor across the output voltage to protect the NeoPixels.

VGD-60

So I’m prepped to do a final test of the NeoPixel ring for power and functionality on a standard Raspberry Pi 3 rig (since it sports an actual header). Once I’ve coded a test and verified that it works then I’ll take the soldering iron to the Raspberry Pi Zero W and wire it in with a quick-connect.

headerwire

I’ve now got the Raspberry Pi Zero W booting with just the power adapter. Note that you can rename its hostname, toggle on the VNC Server, adjust the default screen resolution to your liking and then—in the Finder program in OS X—open up a remote session to its Desktop with vnc://pi@hostname.local, for example. Or, toggle on the SSH Server and connect from a Terminal session with ssh pi@hostname.local.

Have I mentioned how awesome it is to have a fully-functioning computer for $10 (plus $6 for the micro SD)?

And now the power supply is completed and wired to the NeoPixel ring. Everything’s set for 5V DC in at the moment but I may try to adjust the input voltage down to 3.3V later for technical reasons. (The NeoPixels are designed for the Arduino and its output data voltage is 5V whereas the Raspberry Pi is only 3.3V. By adjusting the input voltage down then it makes a 3.3V data line look bigger than it is. There are other tricks like adding a 3V-to-5V data inverter chip but I’d like to avoid that one if possible.)

PowerSupply

Update 3

I’ve smoke-tested the power supply/ring combination and it’s looking good. To make things easier for this step, I’ve now setup a surrogate Raspberry Pi 3 for testing things but since I only had a leftover 4GB microSD, I was forced to use the no-desktop “Lite” Jessie version of Raspbian. But that’s now ready and I’ll likely have some time this weekend to do a basic blink test.