What’s a “digital motor”?

It’s certainly not just a fancy name for an electric motor, but the term “digital” was added by Dyson (I believe) to make his vacuum cleaners sound more exciting. Before that they were known as “brush-less” DC motors.

In simplistic terms, an electric motor works by having a moving electromagnet attracted to a fixed magnet, with the electromagnet on the spinning bit in the middle. Turn on the current and the electromagnet gets pulled towards the fixed magnet. Yeah! We have motion. However, when the two magnets reach each other they’re going to “stick”, so at that point you need to reverse the polarity of the current in the electromagnet so it changes from North to South, and it will then push itself away from the fixed magnet – carry on spinning.

In a traditional motor this is achieved using a commutator, which contains two contacts (+ve and -ve) called “brushes” which wipe against contacts on the spinning bit and provide power to the electromagnet. As the motor turns 180 degrees, the contacts are arranged so that the polarity is reversed – pull becomes push and vice versa, and the motor continues to rotate another 180 degrees – where it repeats.

To run smoothly you need more than two magnets, so something is always pulling, but that’s the general idea.

These brushes are a PITA. They cause friction, wear away, and make sparks. But it’s 19th Century technology and the best we had for a long time.

A brush-less DC motor uses electronics to switch the polarity in the electromagnet. It uses a sensor on the spinning bit to work out which electromagnets need current and when. This can be done with analogue or digital electronics according to taste. Hence someone decided to call it “digital” after a while, because digital was “cool”. However, a digital motor has many advantages – not least of which is getting rid of the hated brushes and the need to replace them periodically. If you have smart electronics the motor can be more efficient by applying exactly the right current for requirements, to more electromagnets. It’s similar in a way to electronic fuel injection motor vehicles (if you’re old enough to remember carburettors) – there’s a chance to put in the right power at the right time, saving energy and improving performance.

An AC motor doesn’t have the commutator problem, because the AC current is changing polarity all the time anyway. You could look at a brush-less DC motor as a AC motor, with the DC converted to AC by electronics.

Wake on LAN with FreeBSD and Broadcom Ethernet

To be fair, the Broadcom Ethernet adapter chips aren’t the best supported by FreeBSD. They’re okay, but for FreeBSD Intel rules the roost at 1-Gig and Chelsio at 10-Gig plus.

Unfortunately you may have no choice, as Broadcom chips are built in to the motherboards on some HP servers; notably the Microservers.

The Microserver Gen 7 is a great little box. I love them. I’m not so keen on the Gen 8 or Gen 10, as they’ve dropped a lot of the features that make the Gen 7 so adaptable.
So after much investigation, I decided to either forego WoL support, or bung in a cheap Realtek card simply to wake them up, but with only two PCIe slots, it was a pity to waste one on a better supported Ethernet NIC. That was a long time ago, and I’ve had one eye out for a fix for a while.

And then last year someone looked at it, and I found references to this in bug tracker. Unfortunately I don’t know who to credit with the fix, and it hasn’t made it to the kernel yet as it’s not 100%, but if you need it I’ve patched the 12.1 driver based on all the notes I could find.

There’s a question about the new driver’s correct operation on laptops. Why you’d be using WoL on a laptop eludes me; but for the Microservers it just works.

Download the patched driver ‘C’ file above (as edited by yours truly – no guarantees), and copy it to /usr/src/sys/dev/bge/if_bge.c, rebuild the kernel and away you go. As it was a bug with the state the chip was left on shutdown, you have to reboot the NEW kernel to shut down in the correct state for WoL to work. Don’t forget to enable WoL in the Microserver BIOS too.

Although this fixes the WoL issue, I know the Broadcom chips are capable of more than the driver – for example jumbo packets. If you want better network performance with a Microserver, add a dual-port Intel Ethernet card instead. Sorry, HP/Broadcom.

FreeBSD in Godden Green

What is going on with FreeBSD in Godden Green in Kent, UK? Jobsite has been spamming me with junior/mid-level programmer roles mentioning FreeBSD for months now, and I’m getting curious!

I have an alert set up so whenever FreeBSD is mentioned I get a ping, as I like to know what’s going on. This isn’t one of the usual suspect AFAIK – they might even be interesting!

The Huawei thing

A few months ago I was asked for comment on the idea that an embattled Theresa May was about to approve Huawei for the UK’s 5G roll-out, and this was a major security risk. Politics, I assumed. No one who knew anything about the situation would worry, but politicians making mischief could use it to make a fuss.

Now it’s happened again; this time with Boris Johnson as Prime Minister. And the same old myths and half-truths have appeared. So is Chinese company Huawei risky? Yes! And so is everything else.

Huawei was founded by a brilliant entrepreneurial engineer, Ren Zhengfei in 1987, to make a better telephone exchange. It came from the back to become the market leader in 2012. It also made telephones, beating Apple by 2018. While the American tech companies of the 1980’s grew old and fat, Huawei kept up the momentum. Now, in 2020, it makes the best 5G mobile telephone equipment. If you want to build a 5G network, you go to Huawei.

Have the American tech companies taken this dynamic interloper lying down? No. But rather than reigniting their innovative zeal, they’re using marketing and politics. Fear, Uncertainty and Doubt.

Some arguments:

“Huawei is a branch of the evil Chinese State and we should have nothing to do with it.”

Huawei says it isn’t, and there’s no evidence to the contrary. The Chinese State supports Chinese companies, but that’s hardly novel. And whether the Chinese State is evil is a subjective judgement.

“Huawei is Chinese, and we don’t like the Chinese State or what it does”.

Really? So we should boycott American companies because we don’t like Trump or what he does then?

“Huawei works for the Chinese secret service and will use the software in its equipment to spy on, or sabotage us.”

First off, Ren Zhengfei has made it very clear that he doesn’t. However, there have been suspicions. In order to allay them, Huawei got together with the UK authorities and set up the HCSEC in Banbury. Huawei actually gives HCSEC the source code to its products, so GCHQ can see for itself; look for backdoors and vulnerabilities. And they’ve found nothing untoward to date. Well, they’ve found some embarrassingly bad code but that’s hardly uncommon.

Giving us access to source code is almost unprecedented. No other major tech companies would hand over their intellectual property to anyone; we certainly have no idea what’s inside Cisco routers or Apple iPhones. But we do know what’s inside Huawei kit.

“Because Huawei manufactures its stuff in China, the Chinese government could insert spying stuff in it.”

Seriously? Cisco, Apple, Dell, Lenovo and almost everyone else manufacturers its kit in China. If the Chinese government could/would knobble anything it’s not just Huawei. This is a really silly argument.

Conclusion

So should we believe what the American’s say about Huawei? The NSA says a lot, but has offered no evidence whatsoever. The US doesn’t use Huawei anyway, so has no experience of it. In the UK, we do – extensively – and we have our spooks tearing the stuff apart looking for anything dodgy. If we believe our intelligence services, we should believe them when they say
Huawei is clean.

Being cynical, one might consider the possibility, however remote, that America is scared its technology companies are being bested by one Chinese competitor and will say and do anything to protect their domestic producers; even though they don’t have any for 5G. Or if you really like deep dark conspiracies, perhaps the NSA has a backdoor into American Cisco kit and wants to keep its advantage?

The US President’s animosity to trade with China is hardly a secret. Parsimony suggests the rest is fluff.

Jails on FreeBSD are easy without ezjail

I’ve never got the point of ezjail for creating jailed environments (like Solaris Zones) on FreeBSD. It’s easier to do most things manually, and especially since the definitions were removed from rc.conf to their own file, jail.conf. (My biggest problem is remembering whether it’s called “jail” or “jails”!)

jail.conf allows macros, has various macros predefined, and you can set defaults outside of a particular jail definition. If you’re using it as a split-out from rc.conf, you’re missing out.

Here’s an example:

# Set sensible defaults for all jails
path /jail/$name;
exec.start = "/bin/sh /etc/rc";
exec.stop = "/bin/sh /etc/rc.shutdown";
exec.clean;
mount.devfs;
mount.procfs;
host.hostname $name.my.domain.uk;
# Define our jails
tom { ip4.addr = 192.168.0.2 ; }
dick { ip4.addr = 192.168.0.3 ; }
harry { ip4.addr = 192.168.0.4 ; }
mary { ip4.addr = 192.168.0.5 ; }
alice { ip4.addr = 192.168.0.6 ; }
nagios { ip4.addr = 192.168.0.7 ; allow.raw_sockets = 1 ; }
jane { ip4.addr = 192.168.0.8 ; }
test { ip4.addr = 192.168.0.9 ; }
foo { ip4.addr = 192.168.0.10 ; }
bar { ip4.addr = 192.168.0.11 ; }

So what I’ve done here is set sensible default values. Actually, these are probably mostly set what you want anyway, but as I’m only doing it once, re-defining them explicitly is good documentation.

Next I define the jails I want, over-riding any defaults that are unique to the jail. Now here’s one twist – the $name macro inside the {} is the name of the jail being defined. Thus, inside the definition of the jail I’ve called tom, it defines hostname=tom.my.domain.uk. I use this expansion to define the path to the jail too.

If you want to take it further, if you have your name in DNS (which I usually do) you can set ip.addr= using the generated hostname, leaving each individual jail definition as { ;} !

I’ve set the ipv4 address explicitly, as I use a local vlan for jails, mapping ports as required from external IP addresses if an when required.

Note the definition for the nagios jail; it has the extra allow.raw_sockets = 1 setting. Only nagios needs it.

ZFS and FreeBSD Jails.

The other good wheeze that’s become available since the rise of jails is ZFS. Datasets are the best way to do jails.

First off, create your dataset z/jail. (I use z from my default zpool – why use anything longer, as you’ll be typing it a lot?)

Next create your “master” jail dataset: zfs create z/jail/master

Now set it up as a vanilla jail, as per the handbook (make install into it). Then leave it alone (other than creating a snapshot called “fresh” or similar).

When you want a new jail for something, use the following:

zfs clone z/jail/master@fresh z/jail/alice

And you have a new jail, instantly, called alice – just add an entry as above in jail.conf, and edit rc.conf to configure its networ. And what’s even better, alice doesn’t take up any extra space! Not until you start making changes, anyway.

The biggest change you’re likely to make to alice is building ports. So create another dataset for that: z/jail/alice/usr/ports. Then download the ports tree, build and install your stuff, and when you’re done, zfs destroy
z/jail/alice/usr/ports. The only space your jail takes up are the changes from the base system used by your application. Obviously, if you use python in almost every jail, create a master version with python and clone that for maximum benefit.

Facebook wants end-to-end encryption

Facebook is wrong. Completely.

End-to-end encryption means that Facebook doesn’t have access to the content of messages. Right now, ONLY Facebook can read your private message content, but that will change. (Actually, that’s not true – your employer can too, and that won’t change, but it’s beside the point)

Given Facebook’s entire business model is collecting and selling personal data on its users, this might sound strange. You can bet it’s nothing to do with making the world a safe place for political activists in repressive countries. Such countries can simply block Facebook.

But there are three reasons they may wish to do this:

  1. Right now law enforcement can ask Facebook for data. If Facebook refuses, there can be a stink. If it hands it over, there can be a stink. If Facebook can shrug its shoulders and say “can’t be done”, it’s off the hook. Apple has done this.
  2. If Facebook’s system is insecure, someone may steal personal data from it in the future, leading to embarrassment and GDPR complications. If it’s encrypted while at Facebook, this cannot happen.
  3. Hard core criminals know all about how to use encryption. Facebook is used for recruiting. If Facebook has to face the music for this, with end-to-end encryption they have plausible deniability.

It’s worth noting that political activists have well established secure communication channels too. Paedophile networks have the knowledge to do this, and do. There are plenty of “dark web” options to keep things secret.

So far from protecting the public, the only reason Facebook has to do this is to protect itself.

Amazon Echo vulnerable in Smart Speaker battle

When Google launched its smart speaker it was playing catch-up with Amazon. The Echo had an established ecosystem, and unless Amazon blew it, this lead looked unassailable. The field was Amazon’s to lose.

Since then, Amazon’s arrogance seems to have taken it towards such a losing strategy. Glitzy launches of new gadgets are not enough to maintain a lead. I have a sample of pretty much every Echo device ever sold, and the newer ones aren’t that much better than the old ones. The build quality was always good, and they work.

What could damage the Echo is the slide in functionality.

Most people assumed that the rough edges – things you should be able to do but couldn’t – would be addressed in time. Google stole a march by recognising the person speaking, but Amazon has caught up. Sort-of. Meanwhile Google has been catching up with Amazon on other functionality and ecosystem.

What Amazon is failing to realise is that they’re selling smart speakers. This is the core functionality. They came up with the technology to link speakers in groups, so you could ask for something to be played “Upstairs”.

This is still there, but it’s been made almost useless. In the beginning you could play anything you wanted on an Echo. All music purchased direct from Amazon was added to your on-line library. There was also Amazon’s Prime music service. The latter has gone down hill recently, with the good stuff moved to a separate “full” streamin service. The ability to play your own music by uploading your MP3 files to your library. This facility has just “gone”, as of the start of the year.

Loyal Amazon customer assumed that it would go the other way, and that you’d be able to stream from your local source to your smart speaker groups. Amazon has blocked this, although some third party skills can play media to a single Amazon speaker. Not so smart.

Now Echo users are about to be hit again. From next month feed of BBC Radio, and other things, is changing. You’ll still be able to get them, but only on a BBC skill. The effect of this is that you can’t use an Echo as a radio alarm clock and more, the alarms will be confined to built in sounds. No longer will I be able to wake up to Radio 4’s Today program at 6am. Unfortunately I will still have to wake up at that time.

Echo Dot with Time Display – but now no use as a radio alarm

Ironically, one of Amazon’s enhancements is an Echo Dot with a time display. Just in time for it to be made useless by the software.

Looking at the change, I also strongly suspect you won’t be able to play a radio station on a group of speakers either. The speaker group technology is limited to Amazon’s own streaming service.

The Echo/Alexa system used to just work. Unless Amazon reverses these catastrophic decisions, it just doesn’t work. And now the public has a taste for this functionally, someone else can walk in and provide it.

Why Python is a terrible language for education

The interpreted language Python is a lot of fun. It’s great for quick and dirty lash-ups, and has list comprehensions whilst being easier to use that Haskell. There are many great reasons why you would never deploy it in a production environment, but that’s not what this article is about.

In the UK, the government decided that schoolchildren needed to learn to code; and Python was picked as the language of choice.

Superficially it looks okay; a block structured BASIC and relatively easy to learn. However, the closer I look, the worse it gets. We would be far better off with Dartmouth BASIC.

To fundamentally understand programming, you need to fundamental understand how computers work. The von Neumann architecture at the very least. Sure, you can teach CPU operation separately, but if it’s detached from your understanding of software it won’t make much sense.

I could argue that students should learn machine code (or assembler), but these days it’s only necessary to understand the principle, and a high level language like BASIC isn’t that dissimilar.

If you’re unfamiliar with BASIC, programs are made up of numbered lines, executed in order unless a GOTO is encountered. It also incorporates GOSUB/RETURN (equivalent to JSR/RTS), numeric and string variables, arrays, I/O and very little else. Just the basic building blocks (no pun intended).

Because of this it’s very quick to learn – about a dozen keywords, and familiar infix expression evaluation, and straightforward IF..THEN comparisons. There are also a few mathematical and functions, but everything else must be implemented by hand.

And these limitations are important. How is a student going to learn how to sort an array if a language has a built-in list processing library that does it all for you?

But that’s the case for using BASIC. Python appears at first glance to be a modernised BASIC, although its block structured instead of having numbered lines. That’s a disadvantage for understanding how a program is stored in sequential memory locations, but then structured languages are easier to read.

But from there on, it gets worse.

Types

Data types are fundamental to computing. Everything is digitised and represented as an appropriate series of bits. You really need to understand this. However, for simplicity, everything in python is treated as an object, and as a result the underlying representation is completely hidden. Even the concept of a type is lost, variables are self-declaring and morph to whatever type is needed to store what’s assigned to them.

Okay, you can do some cool stuff with objects. But you won’t learn about data representation if that’s all you’ve got, and this is about teaching, right? And worse, when you move on to a language for grown-ups, you’ll be in for a culture shock.

A teaching language must have data types, preferably hard.

Arrays

The next fundamental concept is data arrays; adding an index to a base to select an element. Python doesn’t have arrays. It does have some great built in container classes (aka Collections): Lists, Tuples, Sets and Dictionaries. They’re very flexible, with a rich syntax, and can be used to solve most problems. Python even implements list comprehensions. But there’s no simple array.

Having no arrays means you have to learn about the specific characteristics of all the collections, rather than simple indexing. It also means you won’t really learn simple indexing. Are we learning Python, or fundamental programming principles?

Structuring

Unlike BASIC, Python is block structured. Highly structured. This isn’t a bad thing; structuring makes programs a lot easier to read even if it’s less representative of the underlying architecture. That said, I’ve found that teaching an unstructured language is the best way to get students to appreciate structuring when it’s added later.

Unfortunately, Python’s structuring syntax is horrible. It dispenses with BEGIN and END, relying on the level of indent. Python aficionados will tell you this forces programmers to indent blocks. As a teacher, I can force pupils to indent blocks many other ways. The down-side is that a space becomes significant, which ridiculous when you can’t see whether it’s there or not. If you insert a blank line for readability, you’d better make sure it actually contains the right number of spaces to keep it in the right block.

WHILE loops are support, as are FOR iteration, with BREAK and CONTINUE. But that’s about it. There’s no DO…WHILE, SWITCH or GOTO.

You can always work around these omissions:

do
<something>
until <condition>

Becomes:

while True: 
<something>
if <condition>:
break

You can also fake up a switch statement using IF…ELSEIF…ELSEIF…ELSE. Really? Apart from this being ugly and hard to read, students are going to find a full range of control statements in any other structured language they move on to.

In case you’re still simmering about citing GOTO; yes it is important. That’s what CPUs do. Occasionally you’ll need it, or at least see it. And therefore a teaching language must support it if you’re going to teach it.

Object Orientation

And finally, we come on to the big one: Object Orientation. Students will need to learn about this, eventually. And Python supports it, so you can follow on without changing language, right? Wrong!

Initially I assumed Python supported classes similar to C++, but obviously didn’t go the whole way. Having very little need to teach advanced Python, I only recently discovered what a mistake this was. Yes, there is a Python “class”, with inheritance. Multiple inheritance, in fact. Unfortunately Python’s idea of a class is very superficial.

The first complete confusion you’ll encounter involves class attributes. As variables are auto-creating, there is no way of listing attributes at the start of the class. You can in the constructor, but it’s messy. If you do declare any variables outside a method it silently turns them into global variables in the class’s namespace. If you want a data structure, using a class without methods can be done, but is messy.

Secondly, it turns out that every member of a class is public. Always. You can’t teach the very important concepts of data hiding; how to can change the way a class works but keep the interface the same by using accessors.

And talking of interfaces, what about pure virtual functions? Nope. Well there is a way of doing it using an external module. Several, in fact. They’re messy, involving an abstract base class. And, in my opinion, they’re pointless; which is leading to the root cause why Python is a bad teaching language.

All Round Disaster

Object oriented languages really need to be compiled, or at least parsed and checked. Python is interpreted, and in such a way as it can’t possibly be compiled or sanity checked before running. Take a look at the eval() function and you’ll see why.

Everything is resolved at run-time, and if there’s a problem the program crashes out at that point. Run-time resolution is a lot of fun, but it contradictions object orientation. Things like pure virtual functions need to be checked at compile time, and generate an error if they’re not implemented in a derived class. That’s their whole point.

Underneath, Python is using objects that are designed for dynamic use and abuse. Anything goes. Self-modifying code. Anything. Order and discipline are not required.

So we’re teaching the next generation to program using a language with a wide and redundant syntax and grammar, incomplete in terms of structure, inadequate in terms of object orientation, has opaque data representation and typing; and is ultimately designed for anarchic development.

Unfortunately most Computer Science teachers are not software engineers, and Python is relatively simple for them to get started with. The problem is that they never graduate.

Talkmobile APN data settings for Android

If you’re trying to get Talkmobile working with the current version of Android and have tried various settings on the Web with no luck. The Talkmobile web site itself is also incorrect. Here are the real ones as of right now…

Go to “Access Point Names” under setting somewhere. You’ll see Vodafone ones already there, probably. Ignore them.

Create a new one. Call it “Talkmobile” or whatever you fancy. The only three settings you need to change are:

APN Name: talkmobile.co.uk

User name: wap

Password: wap

Proxy: 212.183.137.12

Port: 8799

APN Type: * (if this doesn’t work try “Default”)

I haven’t given the MMS settings because I leave them blank and avoid rip-off charges!