Max’s Cool Beans
By Max the Magnificent
Home working and flashing LEDs
motorised stands that can raise it so I
can work standing up (I fully intend to
make use of this feature… one day soon).
Stay secure and be alert
Fig 1. Welcome to the pleasure dome (my office). Note all the plastic boxes crammed
with cables and components under the desk.
I
don’t know about you, but I’m
in a bit of a tizz-woz at the moment.
As you may know, although I was
born and bred in Sheffield, Yorkshire,
England, I currently hang my hat in
Huntsville, Alabama, US (I moved here
for the nightlife – that’s a little Alabama
joke right there).
Almost a real job
We subscribe to BritBox, so each weekend we get to binge-watch a week’s episodes of Good Morning Britain (GMB).
The UK was put under lock-down a
couple of weeks ago at the time of this
writing. We aren’t under lock-down here
in Alabama, although many other states
are and there are rumours we might be
joining them soon, but we have been advised to work from home if at all possible. Thus, I’m penning these words with
numbness in my nether regions caused
by sitting on a hard wooden chair at my
kitchen table (the things I do for you!).
Actually, I started working from home
at Maxfield Mansions a couple of weeks
ago. Theoretically, as a freelance technology consultant and writer, I could work
from home all the time. In practice, I
rent an office in a building downtown.
My office is lined with bookshelves
bursting at the seams with technical
58
books, science fiction books, and graphic novels – pretty much everything my
wife (Gina the Gorgeous) deems to be
incompatible with the ambience of our
study at home. The office also forms a
repository for my large hobby projects,
which typically feature a lot of strange
sounds and flashing LEDs, and which
are also – inexplicably – denied pride
of place in our family room.
Quite apart from anything else, getting
up at 6:30am each morning, arriving at
the office some time before 8:00am, and
working away till 5:00, 6:00, or 7:00pm,
depending on the work I have in, almost
makes it seem like I have a real job.
I miss my office
Working at home isn’t dreadful. I have my
laptop plugged into a beautiful curved
34-inch monitor that I paid an arm-anda-leg for about four years ago, and that
you can now purchase for peanuts at
local electronics stores, but such is the
way of the world.
However, it has to be said that I really
miss the setup I have in my office, with
my tower computer driving three 28inch monitors that form a single desktop
(Fig.1). The reason the monitor in the
middle is a little higher than its companions is that it sits on one of those
There’s an old joke that goes, ‘Be alert
(the world needs more lerts).’ I didn’t
say it was a good joke. I read with interest Alan Winstanley’s recent Net Work
column (PE April 2020), in which he
discussed various aspects of Internet security, including ‘The curse of cookies,’
‘The rise of the Cookieless Monsters,’
and ‘How browsers leave fingerprints.’
In my case, I have what I consider to
be a reasonably typical setup. As noted
earlier, this includes a tower computer in
my office and a laptop computer at home.
Both are PCs running Windows 10 protected by Windows Defender augmented
by Norton Antivirus. I use Outlook for
my email (the app, not the browser interface), and both of my systems are synchronised via Google’s G Suite, which means
that any email activity (sending, receiving, deleting, moving) on one machine
is immediately reflected on the other if
it is currently active. Alternatively, everything is automatically synchronised
when either of the systems is powered up
and Outlook is launched on that system.
Similarly, all of my data files are stored
in a DropBox folder, so changes made
to any file (including a ‘Save’ while in
the process of editing a file) on one of
my systems are immediately propagated
up into the DropBox cloud. If my other
system is active, those changes are also
promulgated from the DropBox cloud
to the DropBox folder on that system.
Fig 2. My Traveler identified 302
worrisome Wi-Fi networks on the 30minute drive from my home to my office.
Practical Electronics | June | 2020
Fig 3. Goodly Juju and yours truly standing outside my office
(I’m the one in the Hawaiian shirt).
Alternatively, everything is automatically synchronised
when the other system is powered up.
One thing I worry about is ransomware. The idea here is
that you inadvertently get some malware on your system that
encrypts all your files, at which point you are held to ransom
to get them back. The problem from my point of view is that
any such encryption activities would be seen by DropBox
as changes to my files, which would therefore be copied up
into the DropBox cloud. I personally think there should be
worldwide laws and rigorous enforcement for this sort of
thing. When caught, the perpetrators should be hung up by
their short-and-curlies and spend the rest of their lives in jail
(and I say this with love).
Until this happy day is upon us, once a week I disconnect
whichever computer I’m working on from the Internet, perform a full virus scan, plug in an external drive, back-up the
contents of my DropBox folder, to the external drive, unplug
(‘air gap’) the external drive, and reconnect my computer to
the Internet. Of course, there’s always a chance I’ve inadvertently backed-up a sneaky virus, but you can only do what
you can do (also, DropBox has a ‘Rewind’ feature that would
let me regress my account by up to 30 days).
Wobbly Wi-Fi
Do you use a virtual private network (VPN)? If not, why not?
The problem is that when you try to do anything via the Internet, your internet service provider (ISP) can see – and potentially log – everywhere you go and everything you do. Also,
if you are using an unsecured connection, nefarious players
have a much easier task of monitoring your activities and
gaining access to your personal information, like the names
of your cats and the numbers on your credit cards.
The idea behind a VPN – like NordVPN, PureVPN, or
Norton Secure VPN – is that you have a client app on your
home computer. When you run this app, it establishes a
secure, encrypted connection between your machine and
the VPN’s host servers. Now, any information that passes
between your machine and your VPN’s servers looks like
gibberish to any observers, including your ISP, so you are
100% secure, or are you?
Practical Electronics | June | 2020
Well, if your computer is connected to the Internet via a
wired (Ethernet) connection, then a VPN does indeed make
you reasonably secure. The problem arises if you are using
Wi-Fi in a café, hotel, airport... even in your home. The thing
is that the lower layers (2 and 3) of the Open Systems Interconnection (OSI) model aren’t covered by your VPN when you
are using Wi-Fi. In turn, this means that you are susceptible
to rogue access points, evil twin access points, connection hijacks, man-in-the-middle attacks, and so forth.
As one security expert told me, ‘This is like having a house
with a state-of-the-art alarm system, but then leaving your
basement door wide open.’ Happily, the guys and gals at WifiWall (https://bit.ly/2UXP6NV) have developed a technology
they call WiFiWall Dome. Companies can employ a WifiWall
Dome to monitor and secure all Wi-Fi activity on their premises. In the case of ‘road warriors’ who have to leave the protection of the dome, these brave lads and lasses can be provided with WifiWall Traveler units, which we can visualise
as mini-domes, or bubbles.
Sad to relate, WifiWall Travelers aren’t currently available
for individuals, but only as part of a corporate WifiWall Dome
offering. On the bright side, I happen to be in possession of
my own Traveler. How? It’s obvious – I’m special (my mother
always used to tell me I was ‘special,’ and I foolishly thought
she intended it as a complement).
It’s a scary world out there. A couple of weeks ago, prior to
becoming housebound, I powered-up my Traveler, dropped it
in my pocket, and headed to my office. The Traveler constantly
scans any Wi-Fi networks in its vicinity. By the time I reached
my office, it had identified 302 networks as being unsecured
or ‘suspicious’ in one way or another (Fig.2).
Of course, simply being told that there is a problem doesn’t
do you much good. Thus, I’ve informed the Traveler of the
MAC addresses of my tower, my laptop, my iPhone, and my
iPad. The Traveler ‘sniffs’ every Wi-Fi packet that passes by,
paying particular attention to any packets with my name on
them (ie, any of my MAC addresses). If the Traveler sees anything untoward, it will send a command to the relevant device,
instructing it to immediately disconnect from the Wi-Fi, thereby protecting my device and my precious data.
But wait, there’s more, because I was chatting to the folks at
WifiWall just the other day. They tell me that since so many
companies have employees that are currently having to work
from home, they are working furiously (‘nights as the days,’ as
the old Hebrew saying goes) on a new ‘WifiWall Dome for Home’
product that will allow organisations to distribute out-of-thebox Wi-Fi security solutions to each of their employees, where
these solutions will include mini-WifiWall Domes and Travelers.
Simon says
Before we proceed further, I would like to give a shout-out to
PE reader Simon Moore, who hails from Birmingham, England (there is also a city called Birmingham and a town called
Sheffield in Alabama), and who will be ‘chuffed’ to see his
name in print.
It was reading the first column in my Flashing LED miniseries
(PE March 2020) that prompted Simon to purchase an Arduino Uno and a bunch of LEDs and start experimenting. Furthermore, it also prompted him to root through his old issues of the
magazine to track down earlier columns on my BADASS Display (https://bit.ly/pe-jun20-bad). In fact, I just posted a column
discussing Simon’s recent success in using an MSGEQ7 audio
spectrum analyser chip in conjunction with his Arduino Uno
to flash his LEDs in response to sound (https://bit.ly/2R9HdUu).
Arduino for Abecedarians
Speaking of the Arduino, over the past 10 years, I’ve used this
little rascal as a basis for teaching electronics to a number of
59
boasts three 32-bit cores, each running
at 200MHz. Furthermore, unlike the Arduino Mega, each of these cores has its
own floating-point unit (FPU), which
means using floating-point variables
doesn’t slow things down significantly.
And things just keep on getting better
and better, because (a) you can program
the ShieldBuddy using your regular Arduino integrated development environment (IDE), and (b) a NeoPixel library is
available for the ShieldBuddy. My cup
runneth over.
Diggers from Down Under
Fig.4. The ShieldBuddy has enough processing power to make your eyes water.
people, ranging from 14 to 70+ years
in age. I’m currently teaching a friend
called Juju (Fig.3), although I started to
call him Goodly (as in ‘Good Juju,’ meaning ‘Good Luck’), and the name seems
to have stuck.
Why yes, Goodly does seem to be holding a copy of my book, Bebop to the Boolean Boogie (https://amzn.to/2wOVQ8R), I
wonder where that came from. Actually,
Goodly is one of the few people I know
who has read this book from cover-tocover and come back asking for more.
Goodly and his two friends own a
T-shirt printing company. They are all
artists and photographers and suchlike,
but they know absolutely nothing about
electronics and microcontrollers. This is
unfortunate because they are desperately
keen to introduce flashing LED effects to
their T-shirt offerings. On the other hand,
they know me, and if there’s one thing I
do know, it’s how to flash an LED.
Based on working with Goodly, I decided to start a series of articles on my
Cool Beans Blog under the umbrella name
of Arduino for Abecedarians. I posted
the first one a couple of days ago, starting with the fundamental concepts of
voltage, current, and resistance (https://
bit.ly/343kKxy). In fact, the two images
in that column showing a trio of Cool
Beans proudly sporting their V, I, and R
T-shirts which were created by Goodly’s
colleague and my chum, Ronnie.
Flashing LEDs and drooling
engineers – Part 4
As you may recall from Part 1 of this
miniseries, one of my hobby projects is
my Inamorata Prognostication Engine
(see this Instagram photo by <at>PracticalElectronics: https://bit.ly/2UUV2Y0).
NeoPixels are a special form of tricolour
LED that we will be looking at in my next
column. The reason I mention this here
is that, in addition to two knife switches, eight toggle switches, ten pushbutton
switches, five motorised potentiometers,
60
six analogue meters, and a variety of sensors (temperature, barometric pressure,
humidity, proximity), this little scamp
has 83 NeoPixels in the upper cabinet
and 116 NeoPixels in the lower cabinet. Eeek! I almost forgot (looking at the
picture reminded me), there are another
155 NeoPixels powering the five monster
vacuum tubes sitting on top of the engine.
For my first-pass tests, I’ve been powering the various subsystems (furnace,
front panels, vacuum tubes) using a
motley collection of Arduino Uno and
Mega boards, but I’ve known the time is
fast approaching when I’m going to need
a more powerful processing solution.
Well, that solution just arrived in
the form of a ShieldBuddy (https://bit.
ly/2xLZaBq), which was created by the
boffins at Hitex (hitex.com). The first
thing you notice about the ShieldBuddy is that it has the same footprint as an
Arduino Mega (Fig.4).
OK, it’s time for you to sit up and pay
attention because this bit is important.
A standard Arduino Mega is based on
a Microchip ATmega 8-bit processor
running at 16MHz with 256KB of Flash
memory and 8KB of RAM. By comparison, the ShieldBuddy is based on the
Infineon Aurix TC275 processor. These
bodacious beauties are normally only to
be found in state-of-the-art embedded
systems; they rarely make it out into the
daylight of the hobbyist/maker world.
The TC275’s 32-bit processor core runs
at 200MHz and has 4MB of Flash memory
and 500KB of RAM. Pause for a moment
to compare these numbers with those of
the Arduino Mega. To put this another
way, the Arduino Mega’s core manages
only around sixteen 8-bit instructions
per microsecond (µs). By comparison,
the TC275’s core has a 5ns cycle time,
which means it can typically execute
around 150 to 200 32-bit instructions/
µs (1µs = 1000ns).
Oh wait! Did I say ‘core’ (singular)?
Silly me. I meant to say that the TC275
A few weeks ago, I received an email from
PE reader, David R. Humrich, who hails
from Perth, Australia. Like Simon, who
we introduced earlier, David told me that
he’d just finished reading Part 1 of this
miniseries, and that this had prompted
him, in his own vernacular, to ‘get off
my bum and into the vast pile of Arduino stuff I’ve collected over the years.’
A few days later, David emailed again
to ask if I was familiar with the Duinotech 8x5 RGB LED Shield for Arduino
(https://bit.ly/2Jz5mQ0). I wasn’t, but I
have played with a somewhat similar
8x8 NeoPixel-based shield before, and I
told David that an interesting little program with which he might want to experiment would be a ‘worm’ crawling
around the display.
The idea here is that you have one pixel
for the worm’s ‘head’ and a couple more
pixels for its ‘body.’ You light the head
and the body with different colours, and
you set the worm to randomly meander
its way around the display. In addition
to being visually appealing, this is a great
little task that can facilitate learning a lot
of C programming tricks. I sent David a
link to a video of just such a program
running on my 8x8 display (https://bit.
ly/2R5TfOn).
Let’s take the red pill
Do you remember the first Matrix movie
where Neo has to choose between taking
the blue pill or the red pill (https://bit.
ly/39AW2Wo)? As Morpheus says: ‘You
take the blue pill – the story ends, you
wake up in your bed and believe whatever you want to believe. You take the
red pill – you stay in Wonderland, and I
show you how deep the rabbit hole goes.’
Well, I’m afraid I opted for the red pill,
because my dialogue with David has
prompted me to plunge headfirst into
my own rabbit hole to build a magnificent matrix based on ping pong balls illuminated by NeoPixels – something like
the ‘Video Wall’ you can see on YouTube
(https://bit.ly/3aG1itl).
My first pass is going to be a small 12
× 12 = 144 ping-pong prototype. At some
stage in the future, I intend to construct
Practical Electronics | June | 2020
T op v iew
3
4
1
1
S ide v iew
2
3
4
1
2
3
= R ed anode
= C om m on c athode
= G reen anode
= B lue anode
2
4
Your best bet since MAPLIN
Chock-a-Block with Stock
Fig.5. A regular tricolour LED.
Visit: www.cricklewoodelectronics.com
Or phone our friendly knowledgeable staff on 020 8452 0161
Components • Audio • Video • Connectors • Cables
Arduino • Test Equipment etc, etc
U p/ Off/ I nac tiv e
C enter ( from
U p)
D own/ On/ A c tiv e C enter ( from
D own)
U p/ Off/ I nac tiv e
Fig.6. Using a tricolour LED with an SPCO switch and with two
colours for the centre position.
a much bigger version. I just took delivery of five meters of
30-pixels-per-meter NeoPixel strip from Adafruit (https://bit.
ly/3dOa5v4). I also received 288 ping-pong balls (I always believe in having spares) from Amazon, where they cost only
$11 for a pack of 144 in the US.
These aren’t game-quality balls, but they are more than good
enough for what I’m going to do with them. I will, of course,
be reporting further in future columns.
Over the rainbow
Did you ever see the video of Israel ‘IZ’ Kamakawiwoʻole singing Somewhere Over the Rainbow while playing the ukulele
(https://bit.ly/34cx0f5)? In fact, it was seeing this video that
prompted me to build my own ukulele, but that’s a story for
another day.
First, I haven’t forgotten that we looked at bicolour LEDs in
my previous column (PE May 2020) and that I still owe you a
sketch (the file is CB-Jun20-01.txt – now available for download from the June 2020 page of the PE website) and a video
(https://bit.ly/2XiVli0) relating to the 2-terminal device.
Well, the next step up the ladder is to use a tricolour component, which contains red, green, and blue LEDs (Fig.5).
I’m using Chanzon 5mm RGB LEDs, which you can purchase
in 100-piece packs from Amazon UK for only £5.18 (https://
amzn.to/2x1mc7l).
According to the datasheet, the red diode has a forward voltage drop of 2.0 to 2.2V (we’ll assume 2.0V), while the green
and blue diodes both have forward-voltage drops of 3.0 to 3.2V
(we’ll assume 3.0V). Furthermore, the datasheet says that all
three diodes have maximum forward current values of 20mA.
From previous columns, we know that this means we’ll need
to use a 150Ω current-limiting resistor in series with the red
diode, and 100Ω resistors for the green and blue diodes.
If we just turn our three diodes on and off, we can achieve
23 = 8 different colours: red, green, blue, yellow (red + green),
cyan (green + blue), magenta (red + blue), white (red + green
+ blue), and black (all off).
Alternatively, if we use 8-bit pulse-width modulation (PWM)
to control the brightness of each diode (PE March 2020), this
means each diode can have 256 different levels. Thus, mixing all three diodes
allows us to achieve 256 × 256 × 256 =
16,777,216 different colours.
For the purposes of this column, assuming the use of a single-pole, centrePractical Electronics | June | 2020
Visit our Shop, Call or Buy online at:
www.cricklewoodelectronics.com
020 8452 0161
Visit our shop at:
40-42 Cricklewood Broadway
London NW2 3ET
off (SPCO) switch (PE May 2020), we will use our tricolour
LED to generate only four colours: red, green, yellow, and
orange. We’ll use red to indicate when the switch is Off/Inactive, green to indicate when the switch is On/Active, and
either orange or yellow when the switch is in its center position to provide an indication as to its previous state (Fig.6).
You can download a sketch (file CB-Jun20-01.txt – available
on the June 2020 page of the PE website) and watch a video
(https://bit.ly/3b6hDYx) to see all of this in action.
Next time
Standard tricolour LEDs can be a lot of fun, but they also have
several disadvantages, not least that they each require three
output pins from our microcontroller to drive them.
By comparison, the NeoPixels we will be looking at in my
next column each have only four pins: 0V, 5V, Data-In, and
Data-Out. Each NeoPixel contains a little controller along
with three 8-bit PWMs (one each for its red, green, and blue
LEDs). As we will see, we can daisy-chain these little beauties together, allowing us to control hundreds of pixels with
a single pin from our microcontroller.
As always, I welcome your comments, questions, and
suggestions. Until next time, be safe, wash your hands,
drink cold lemonade (responsibly, and assuming you are
of drinking age), eat hot bacon (or cheese) sandwiches, and
wear Hawaiian shirts (Hey – it works for me).
Cool bean Max Maxfield (Hawaiian shirt, on the right) is emperor
of all he surveys at CliveMaxfield.com – the go-to site for the
latest and greatest in technological geekdom.
Comments or questions? Email Max at: max<at>CliveMaxfield.com
61
Max’s Cool Beans cunning coding tips and tricks
I
n my previous column (PE May 2020), I promised
that this month we would consider how the << and >> operators
perform their magic. Sad to relate, we are going to have to
kick this one down the road because reader David R Humrich,
who hails from Perth in Australia, emailed me with a rather
interesting question relating to the use of curly brackets { }.
Before we look at David’s question, let’s first remind ourselves
that { } can be used to create what is called a ‘compound statement.’ This is the mechanism used by the C programming language to group multiple statements into what can be thought of
as a single statement.
Consider, for example, what happens when we define a function called MyFunction ():
void MyFunction ()
{
// Pretend this comment is a statement
// Pretend this comment is a statement
// Pretend this comment is a statement
}
When we call this function from somewhere else in the program, the computer ‘sees’ all of the statements in the function
as forming a single logical entity.
The same thing happens if we use { } along with a control
statement like an if (). First, let’s assume that if the condition
is true, we only wish to perform a single action, in which case
we could write this as follows:
if (done == true) fred = fred + 1;
statement in the middle of a function – by ‘standalone,’ we
mean that it’s not associated with a control statement like if
() or for ().
In fact, this is perfectly legal. If you wish, you can simply
use { } to gather a group of statements together to make it clear
to yourself and anyone else that you consider these statements
to be related. These are often referred to as a ‘block,’ and using
this technique may be referred to as ‘block programming.’
You can also have nested { { } } to whatever level you
desire. But the really interesting thing is that, in addition to
statements, your blocks can also contain variable declarations.
Why is this interesting? I’m glad you asked. In my previous
column, we talked about global and local variables. We noted
that global variables are declared outside of any function and
can be seen and modified by any function. By comparison,
local variables are declared inside a function and can be seen
and modified only by the function in which they are declared.
We also talked about the ‘scope’ of a variable, which refers
to the extent to which that variable can be seen. For example,
if we declare a variable as part of a for () loop, the scope
of the variable is limited to that loop (PE, May 2020). Well, if
a variable is declared inside a block, its scope is that block;
that is, it cannot be ‘seen’ outside of the block, even by other
parts of the function in which the block resides. Consider the
following ‘nonsense program’ example:
int John = 6;
void MyFunction ()
{
int jane = 9;
Now, C doesn’t care how many whitespace characters we use, so:
{
if (done == true)
fred = fred + 1;
// First block
int bert = jane + John
// More stuff
}
We are, of course, assuming that the variables done and fred
have been declared elsewhere in the program. Now, suppose that
we want to perform several actions if our condition is true. One
way to do this would be as follows:
{
// Second block
int jack = jane – John;
// More stuff
}
if (done == true) fred = fred + 1;
if (done == true) jane = jane – 1;
if (done == true) bert = fred + jane;
In addition to looking silly, this is inefficient because we are
performing the same test three times. This example calls out to
us to use a compound statement as follows:
if (done == true) // Equal to above
{
fred = fred + 1;
jane = jane - 1;
bert = fred + jane;
}
In this case, a compound statement is both more efficient and it
makes it clearer what we are trying to achieve.
Back to David
Returning to David’s question. He asked what would happen if
one were to use { } and hence create a standalone compound
62
}
Remember that I use initial uppercase and lowercase letters
for my global and local variables, respectively (PE April 2020).
So, John is a global variable whose scope is every function
in the program, while jane is a local variable whose scope
is limited to MyFunction (). By comparison, the scope of
bert is limited to the first block, while the scope of jack is
limited to the second block; neither can be seen outside their
respective blocks.
Dividing a large program into a number of smaller, well-defined functions makes it easier to test each function in isolation and reuse functions in different programs. Similarly, one
advantage of using a block-based technique to limit the scope
of variables is that it makes it easier to reuse those blocks in
other functions and other programs.
Next Time
I’m not going to say what we’ll be looking at next time because
things change quickly around here (I’ve learned my lesson).
We’ll all just have to wait and see. Until then, have a good one!
Practical Electronics | June | 2020
