Archive for the 'Technology' Category

The root of the problem

Sunday, August 23rd, 2015

The other day, I did something a bit unwise, and power-cycled my Volumio music player, and it failed to return to life. Eventually I got it hooked up to a TV to see what was wrong, and predictably:

Give root password for maintenance (or press Control-D to continue)

Unix and Unix-like systems don’t like having their power shut off without a clean shutdown, and the Raspberry Pi seems particularly prone to corrupting the root filesystem given a bit of provocation.

Now, generally, using fsck is like using chkdsk on Windows. It might fix things, or it might break them more. Not a big issue with what is quite a small image on an SD card, so breaking out dd soon should fix that: the music is on an external drive, and there’s very little config to do.

Except it didn’t. I wrote the image, and tried again. Many times, with new SD cards, even with a USB-microSD adaptor in case the laptop I was using had a duff SD slot, and also tried my other Raspberry Pi. each time, it failed. After much fscking about (literally) I realised the one thing I hadn’t changed. A Raspberry Pi runs off a micro-USB phone charger, and instead of the usual, decent quality one I used where the Pi is installed, I used a cheap nasty one that was handy. Evidently it wasn’t stable enough.

With it booting correctly and back in place, back to the music, and I’ve just discovered another great thing. As Volumio is based on MPD, you can either use the (very nice) web interface built-in, or connect a client like Cantata:

Cantata's interface- plays the music, gives info.

Cantata’s interface- plays the music, gives info.

or one of the multitude of others,and control from a phone, tablet, or PC.

I can’t help but wonder how many commercial jukeboxes are using this stuff in the backend…

CAN do?

Tuesday, July 28th, 2015

I’ve written before about CANbus, and electronics in cars. My own car, despite being only a mid-size, mid-range hatch a few years old, has a good few electronic modules, and CANbus to connect them. Cars have 3 flavours of CAN- one for the drivetrain and chassis- so this episode would use that, as would this one, and one for the interior stuff (for both instrumentation, and stuff like the radio shifting it’s volume up and down with speed, or automatic closing of windows when locking), and then one more for connecting diagnostic gear like VCDS or Torque.

These individual networks are gatewayed together as they run at different speeds, and there’s no real control over what can talk over these networks, which isn’t really a problem, you’d think: the car is a closed system, so unless you connect diagnostic equipment or get very interested and attach a Raspberry Pi to the CANbus (great article there), it hardly matters. There have been scare stories in the press of clever people hacking cars before, but these have involved a direct, cable connection to the diagnostic port, so no big deal, and the networks *have* to be gatewayed for the instruments to display your speed, and for the diagnostic kit to work.

Until…..

It is now becoming commonplace to include connected entertainment systems into cars. These will have an internet connection, either via a tethered mobile phone, or with a SIM card fitted. There’s various names for this, according to manufacturer.

There’s Audi Connect, GM OnStar, Ford Sync, for example, and then there is Fiat Chrysler UConnect.

The scary bit here is that potentially, you’re now exposing the CAN to the Internet. Depending on how well secured things are (or aren’t), you might possibly allow anyone on the Internet to, say, disable the brakes or transmission, as detailed here by The Register. As we get more and more fancy devices (like, say, auto-parking) then the exposure of safety-critical things like steering and braking, which used to be simple, mechanical, systems to attack becomes greater.

It’s certainly the case that some cars (VAG ones, for sure, in my experience) only allow full access to some critical modules with a login- but these logins are quite well publicised, which means you’d better be pretty sure about your car’s fancy entertainment system being secure, and staying secure when it is 15 years old and the manufacturer no longer supports it. Maybe the further research of these guys, with intrusion detection for CAN has merit?

Turning the wheels

Thursday, July 2nd, 2015

As I’ve been recovering from surgery, I’ve not been using my car, so to preserve the battery (now around 9 years old), I connected (well actually, my other half connected) my excellent CTEK battery charger, at first using the croc clips, then, when I was able to, using the comfort connector- a socket that is connected to the car permanently.

Doing this upset things: when I went to try and start the car, I got a load of warning lights, and plugging in the diagnostics revealed a fault code for the steering angle sensor:


00778 - Steering Angle Sensor (G85)

Clearly dicking about with the battery terminals had lost the basic setting.

The sensor simply tells the ECU how far the steering wheel has been turned, and is needed, and calibrated, so that the Stability Control knows which way the wheels are pointing, and also so the Steering Assist ECU can adjust the steering weighting according to speed and how much steering lock is applied. As such, you have to tell the Stability Control (part of the ABS controller) where straight ahead is, with this procedure, and then allow the car to calibrate where the two ends of travel of the steering rack are by following this procedure, which is why it’s remained undone until now, now I’m able to drive short distances and manage the steering with little power assistance.

In the event, it took several attempts at the second procedure, which is why today found me sitting in an quiet industrial estate, with the car running and a laptop on the passenger seat, and even then, it took a short drive and several lock-to-lock moves to clear. The steering was both very heavy and devoid of feel until all of a sudden, the fault lamp cleared, the steering got lighter, all started working correctly, and a scan produced this:

A happy steering assistance ECU

A happy steering assistance ECU

All a bit complicated, really, but that’s the price we pay for all the fancy active safety gear, and another sign of how car systems interact: the steering angle sensor will report an error in the steering assist ECU, but the basic settings are set in the ABS/Stability controller, and both controllers get upset if this setting is lost.

Digital Motor: Marketing bollocks?

Thursday, May 28th, 2015

I’m bored evidently.

The Dyson adverts on TV got me thinking: they go on about a Dyson Digital Motor. It sounded like bollocks; marketing fluff, so I asked them, and to their credit they answered:

Our digital motors different from regular motors in that they do not contain carbon bristles that create motion within the motor. Regular motors function by way of these carbon bristles allowing certain parts of the motor to rotate, but the use of this equipment can be noisy, heavy and produce fumes. Dyson opt for a digital motor that employs electronics and magnetic equipment to create power and motion within their machines with digital equipment inside the motor than controls the levels of power being produced by the machine. This more advanced design allows for a more powerful motor that is not only lighter, but more efficient in the long term and quieter when functioning.

So, it’s a brushless motor, with some control electronics. Maybe not marketing fluff after all. A quick google reveals this article in electronics weekly– so there really is some clever engineering- the digital bit is a microproccessor switching the supply quickly in order to make the brushless motor work on DC at very high speed. I take it back- not marketing fluff, and full marks to Dyson for answering tedious little queries.

A bit more googling reveals this press release (.doc, 35k) from 2003 with some details of an earlier version. Love the diagnostics…

Volumio

Wednesday, January 14th, 2015

I already mentioned my plans for a media streaming server with my Raspberry Pi, and finally got round to it: a friend donated an external disk enclosure that took a pair of 1TB SATA disks, and presented them as a 1TB RAID 1 volume over USB. A cheap USB hub, a case for the Pi, a £2.49 USB wifi dongle, and a quick download of Volumio (a modified Raspbian image) and all the bits are present, fitting them together was pretty simple, and I have a working media server with great sound quality, that uses little power and is completely hidden from view: all the hardware worked, with the only tweaking being a quick edit of /etc/network/interfaces to set a fixed IP on the wireless network.

Volumio is cool: it’s like IPCop in that it’s an open-source appliance based on Linux with a web interface to configure it and use it, but you can delve “under the hood” with ssh. It uses the mpd server, and presents itself on the network via SCP or a SAMBA (Windows network) share for uploads, and advertises on Airplay or DLNA. You can control it with a wide range of clients for all sorts of devices as well as the web interface, and it just found my DAC with no tinkering, and the sound from a FLAC file is as good as the original CD, even with the Pi’s limited horsepower.

I have a good amount of ripping to do…..

Into the Digital Age

Sunday, December 28th, 2014

Regular readers will know that I’ve got some prejudices about audio: for years I didn’t have an MP3 player, eventually relenting, although I still don’t do actual MP3s, and buy music almost exclusively on CD, though it has to be said, my views on downloadable music 10 years ago are starting to be disproved: MP3 at a highish bitrate (which is more practical with increasing bandwidth and storage) is good enough for most people, on most systems, at most times, and lossless formats are becoming more common, especially since Fruitco introduced their lossless format (though of course, they should have introduced it as an open format…).

One thing* has kept me away from using a computer to play music in the house: the analogue outputs of most consumer PCs (and I’m including Fruitco in this) hardware is a bit ropey- but then again, it was never intended for high-quality audio.

Enter the DACMagic. It’s a proper (though very small) hifi component with TOSLink, S/P DIF and USB inputs, and it’ll do the high sample rates that may not be neccesary, but more importantly, it’s a decent DAC chip with the compromise pushed a bit towards quality, and some initial testing sounds as good as the CD with a FLAC file (and, pleasingly, the device was recognised and working within seconds on Ubuntu).

The plan now is a Raspberry Pi and Volumino: the Pi’s analogue audio output is particularly compromised (hardly surprising given it’s a £35 computer) and the ‘proper’ stereo doesn’t have HDMI. There are cheaper ways to get better Pi audio with a Wolfson DAC, but as a bonus, the DACMagic’s inputs can link to my existing CD player too; a respectable but budget Marantz, and also, it comes in a nice black case that looks decent next to the other gear: initial comparisons sound like the DACMagic has improved sound here too, but that could be the confirmation bias- I’ve just bought it, so it /has/ to give an improvement :-).

*OK, two things. I’m an awful luddite, it would seem.

Updated Android

Sunday, November 23rd, 2014

I’ve had a Samsung Galaxy S2 for about 2.5 years now, originally bought as a Vodafone contract handset. It’s a great phone; nicely put together and reasoanably durable and powerful, but of late I’d got it in my head that the version of Android was getting on, and the combination of Samsung and Vodafone apps over the top annoyed me and cluttered the OS.

Enter Cyanogenmod, a community-generated derivation from the Android source. As the S2 is a popular device, it’s well supported, and a quick prompt from a nice chap on Twitter pointed me in the right direction, and with a few Android developer tools installed on Ubuntu ( damned site easier than Windows), I was done. With the phone rebooted, I’ve got Android Kitkat, no Vodafone bloat, and a generic Android interface, and seemingly, better performance and battery life :-)

Digital Audio in a FLAC

Wednesday, October 15th, 2014

Reading The Register earlier this week, this story popped up.

I thought it was interesting that the article talks about various encoding methods, master tape quality, speaker and amplifier quality, and the problems of re-encoding into Apple lossless (full marks, incidentally, to Fruitco for implementing a lossless codec, though why not use FLAC?), but manages to skip over a critical point of digital audio: the DAC.

There is of course, a lot of bollocks spoken and written about audio: this leads to crap like what this article is handily debunking, *edit* LOL */edit* but one thing is for certain: if you’ve picked a god encoding scheme and a decent bitrate, the digital path is less important than the analogue one (digital signals do not degrade gradually, analogue ones do) and the quality of the conversion is critical.

The analogue stages in most phones and computers is simply not designed for high quality, and the article doesn’t mention this: if you’re using a PC or a phone to play music, if you’re fussy, you really need to do the conversion externally to the PC itself- so either amplifier with a digital input and a PC with digital out, or a USB DAC, or maybe good bluetooth headphones, though there’s a caveat on compression and limited bandwidth with bluetooth audio, which may mean you lose what you gain, but having said that, given that bluetooth headphones are likely to be used on the move with a lot of background noise, it’s probably not important.

Surface Treatment

Saturday, September 6th, 2014

A few days ago, we got a Microsoft Surface Pro 3 at work. It’s not a bad machine: it’s a Laplet: a hybrid laptop/tablet, and it works well, if we excuse it for Windows 8- the hardware is nice, thin, light, and i7 versions are quick, so it’s a good fit for the very mobile staff that
will be using it.

I remain convinced that Win 8 is a bastardisation of touch-screen tablet OS and a desktop OS that feels like an unholy marriage, though I’m hating it less as I get used to it.

What really creates a whinge is this little stroke of genius, which caused a support call and much fannying around testing chargers this week.

You can see the product launch meeting now:

Dilbert

Yes, Microsoft launched a device, launched a dock for it at the same time (we got the dock a day or two after the device itself), and managed to make the two not work together at launch. Cue a large loss of faith in what should be a good product.

*facepalm*.

You see this a lot with technology, and come to that, with poorly managed processes outside of tech:

1. Decide on arbitary launch date and fix everything to that.
2. Skimp on the preparation/testing, or ignore the problems.
3. Wonder why it’s all gone wrong.

The result is pretty much as you’d expect; you look inept…

Dirty Boy

Tuesday, July 29th, 2014

I’ve gone on here before about how web filtering is wrong and doesn’t work properly, and how the bigger the scale, the harder it is.

We’ve also seen that, according to an Ofcom report (PDF, 1.1MB) customers have greeted the filters with rejection.

That’s quite gratifying, I think. People are being actively prompted to allow censorship, and are rejecting it. Of course, that the tech required is now in place will make it easier to do more packet inspection should law (or other means) request it…

Here’s the Open Rights Group‘s take on it, the approach is humourous, but the message is serious.

If you think this won’t happen, try the Scunthorpe Problem for size.

I’m personally of the opinion that an ISP should do one thing: provide the infrastructure to route packets to the internet, and maybe a few basic services (like DNS, SMTP etc). You might note that the sponsors of that video refuse to offer a filtered connection, something they’re to be congratulated on.

If, like me, you want to defend an open, uncensored Internet with reasonably privacy, then consider joining the Open Rights Group or the Electronic Frontier Foundation. Note that ORG is a UK organisation, EFF is US-based.


This blog is protected by Spam Karma 2: 38980 Spams eaten and counting...