pavelmachek

Slides from openmobility talk

Tue, 14 May 2013 12:54:47 GMT

...are here. Recording was going on, but I'm not sure if it is online somewhere...

From squeeze to wheezy and back, and how not to backup your / filesystem

Thu, 09 May 2013 12:20:07 GMT

I'm still running squeeze on my X60... and I decided that with wheezy becoming "stable", it was good idea to upgrade. Before I started, I did back up my root filesystem (fortunately), with

cp -a --one-file-system / somewhere

Upgrade was a bit of fight (like aptitude trying to take hours of cpu time), but eventually I succeeded... Only to realize that system no longer boots into GUI and (worse) that gnome2 is gone. I'm not great fan of gnome3; definitely on X60, anyway. Its animations feel excessive even when system is unloaded, if there's some background load it quickly becomes unusable. I googled a bit, and it did not look like going back to gnome2 is not exactly easy.

So I went back from the backup. First, chromium refused to run because new version broke the config files. I restored those from backup. But next... strangely my self-compiled 3.9 kernel stopped working. Stock debian kernel kept running, but own kernel ran init then rsyslogd broke the boot.

Can you guess what went wrong?

pc jvgu bar svyr flfgrz bcgvba vf ernyyl onq vqrn; vg jvyy abg pbcl rirelguvat sebz lbhe / svyrflfgrz, va cnegvphyne vg jvyy abg pbcl /qri, orpnhfr gurer'f gz csf zbhagrq bire vg. Bhpu.

What should computers learn

Fri, 26 Apr 2013 13:01:23 GMT

Ok, so I have small herd of computers -- Thinkpad X60, AMD desktop, ARM "tablet", Nokia N900, Nokia 6151, TI Chronos smartwatch. All but 6151 and chronos run Linux, all are programmable, and I have root access on all but Nokia 6151.

Yes, I should probbly get some light and cheap android as 6151 replacement. Light and cheap because it will go on horseback with me, and should have powerful at least 60mW led... because that's important in woods. I'm thinking about Alcatel v860 (old android) or Gigabyte Gsmart g1342 (unsure rooting)... suggestions welcome..

I somehow assumed that having machines under control and running Linux would make them well-behaved, solve world hunger, and make them behave as they do in movies... and yes, it is nice to be able to ssh around and to run same app on most machines.

But happy new world did not happen.

Phones have concept of "behaving themselves", like quiet profile, and I did program automatihc profile switching -- sl4a for android is nice, and that's part of reason I ported it to maemo. Unfortunately, desktops/notebooks do not even have that much... and tend to wake me, or worse (wake my girlfriend).

Another thing PCs should learn from phones is concept of loud speaker and headset. Using headset is pretty much requirement for VoIP telephony, but incoming rings should go to the loudspeakers... even if headset is plugged in. (Currently, I have USB speakers connected for loudspeakers. Yes, twinkle can select soundcards for ringtone and voice separately; but these should be system-level options, not app-level.)

What more would I like? It should be easy to do remote access between my machines; I should not have to search for cell phone to read incoming SMS, or do anything with the small keyboard when I'm near PC. Yes, ssh exists and I use it a lot, and vnc for n900 exists, too... but it has all to be configured separately. When I open web page on a PC and start reading, it should be easy to finish reading on other computer. I now use chromium, so maybe it is doable, but I'd really prefer to use my server, not google.

I'd like my machines to synchronize contact and calendar entries. At least this seems to be mostly working, thanks to owncloud. I'd like machines to automatically back each other up. I have some scripts for that, but they are a bit hacky and far away from automatic. And there's more that should be done...

Nokia n900 is too close to Zaurus

Sat, 20 Apr 2013 11:39:57 GMT

You know what is the most annoying misfeature of Sharp Zaurus sl-5500? They spared few cents, and did not provide real time clock.

Do you know what is the most annoying misfeature of Nokia N900? Yes. They failed to provide real time clock. actually... it seems to be misfeature of whole Nokia line, including old Nokia 6151.

Now... if you try to swap simcards between two Nokia phones, that's when the fun starts... because you are likely to lose all the time sources.

Bad Nokia.

25000 points for openwlanmap project

Wed, 17 Apr 2013 12:59:37 GMT

openwlanmap was emptier than openbmap, but unfortunately I could not figure out how to upload there. Figuring out Openwlanmap upload took a while, too, but I succeeded in the end.

Oh, and based on openmobility feedback, I created "fusion" script to determine position from multiple sources, assuming limit on speed user moves. In the progress, I did some measureemnts. 95% of all "current GSM cell" situations seem to be less than 4.8km from the cell. That was expected. But the same number for wifi is very high: 95% of all "wifi detected" situations fits within 2.8km... Either omnidirectional wifi has way longer range then I expected, or there's something wrong in the measurements. That was with n900.

TI Chronos surprise

Mon, 08 Apr 2013 12:49:56 GMT

I picked up TI Chronos after long time -- like half a year. (Yes, I'd like to know if Pebble smartwatch is lighter than this... because chronos are a bit too heavy for me.) And I was surprised: time on watch actually matched time on thermometer.

...which was very surpising, given that DST changed in the meanwhile, and given that chronos had trouble keeping good time.

Well... it turned out I was really lucky: chronos was day off. (And then I realized that I did not update thermometer to DST. I hate DST. Changing timezone twice a year is stupid.)

openmobility position talk

Sun, 07 Apr 2013 22:15:53 GMT

Openmobility conference was nice... All the promising cellphone platforms around, 2 3D printers and a plane with camera as a bonus.

If someone is interested, slides are here. And yes, contributing GSM cells do the databases is as easy as walking around with Android phone and suitable application. Czech republic has ~50% cell coverage now, so GSM positions are already usable, and it will only get better...

Horse vs. human

Thu, 04 Apr 2013 11:14:58 GMT

Czech newspapers have article on human vs. animal performance. They claim that horses have top speed around 30 km/h and can't compete with humans on long distances. Well, top horse speed is above 60 km/h (ponies can do 30km/h), and yes they can mostly beat humans on long distances.

Anyway, I always wanted to do horse vs. human races... I'll provide the horse (slightly-trained fjord). Any humans?

openmobility conference

Fri, 22 Mar 2013 20:02:04 GMT

It looks like I'll be speaking on openmobility conference in Bratislava. Talk will be about various positioning system, so basically GPS, positioning using GSM and wifi.

I wondered why monav stopped working on n900

Thu, 21 Mar 2013 22:54:27 GMT

...and yes, I did suspect map format update. It turns out I was right. Thanks to PocketBook hackers monav works for me, again... making n900 way more useful. I just wonder if there's better place to download data maps than uloz.to...?

Flash memory... and are there reasonably small cellphones

Fri, 08 Mar 2013 11:00:36 GMT

The race for the smallest cellphone stopped around time of Ericsson T68... too bad. There are still some small cellphones -- 40g does not look bad, but... I'd really like the race to continue. That does not mean I'm going to give up the Nokia n900, it means I'd like something small for the secondary phone.

Given all the problems I've seen from flash cards, I'd expect SSDs to be unreliable. There's now some evidence SSDs have problems. I'd really like to see the product names... I believe they did one think wrong in the story: as SATA is based on sectors, they should not expect atomicity of 4K blocks.

And on the related note, it looks like SD cards are not as bad as they usually are, you just have to be very careful about formatting. Would not it be nice if mkfs did this automatically?

So, these days distributing malicious software is considered okay?

Mon, 11 Feb 2013 12:42:05 GMT

I have seen uglyness in EULA's before, but... this is scary:

DIGIPEN MAKES NO WARRANTIES OR REPRESENTATIONS THAT THE GAMES SOFTWARE IS FREE OF MALICIOUS PROGRAMMING, INCLUDING, WITHOUT LIMITATION, VIRUSES, TROJAN HORSE PROGRAMS, WORMS, MACROS AND THE LIKE. AS THE PARTY ACCESSING THE GAMES SOFTWARE IT IS YOUR RESPONSIBILITY TO GUARD AGAINST AND DEAL WITH THE EFFECTS OF ANY SUCH MALICIOUS PROGRAMMING.

(From game called Perspective).

What to do if your president goes crazy?

Mon, 11 Feb 2013 11:04:03 GMT

Happened here. It started with stealing of pens. Then he let people out of jail, and stopped prosecution of serious stuff going for more than 8 years... meaning felonies from "giving up state property" phase went uninvestigated. Then he said "oh truth won our presidental election" about candidate that was pretty obviously lying (mild attack on Havel, too). Now he started attacking late president Havel in pretty nasty ways...

Unfortunately, prosecuting president is pretty much impossible to do. Shooting him proved easy, on the other hand, but unfortunately wrong kind of ammunition was used. (He deserves something not so easy to wash away, at the very least.)

Push-to-talk over email for n900

Sun, 10 Feb 2013 21:47:52 GMT

I updated tools at tui/maemo. They now include:

loc.py: Estimate location based on GSM cell info and opencellids.

chmi.py: (For czech users) Get current position and load CHMI weather data with current position displayed.

myptt: Record voice message, then send it via email.

fakegpsd.py: Export gps position using gpsd interface. (Enables you to run rana on cellphone.) Very bad hack, should use threads.

Where do old android applications go?

Fri, 08 Feb 2013 21:07:12 GMT

I used to be running Waze and Push-to-talk lite. Unfortunately... newer versions no longer support HTC Dream
(with its android 1.5). Unfortunately, I was foolish enough to uninstall application (or in case of waze, it simply broke), and now it is no longer possible to install. Oops.

(If someone has copy of Waze old enough to run on android 1.5, let me know. Waze client is GPLed, so that should be legal.)

Speaking of push-to-talk... Push-to-talk over email is surprisingly simple, fast and usable. Typing on cellphone sucks, but speaking a message is not a problem, and sending PTT message is not latency sensitive, so it is fine over GPRS. I may even try to code it for N900. (And if someone already has something similar, please leave a comment).

Android emulation for single process

Fri, 08 Feb 2013 21:03:21 GMT

Single-process emulator... is there one somewhere? Blackberry seems to use one, too (any idea how it is called?), but I can't find them. Apparently Myriad Alien Dalvik was second attempt (and they got it running on n900, but it seems to be waporware). I believe android emulation is going to be very very important very soo -- because of all the local apps. I tried downloading android sources, but even that is non-trivial, and compiling them is apparently also non-trivial... Like weekend project.

Hand warming and blinding device that is trying to get you killed (with a complimentary flashlight)

Wed, 23 Jan 2013 11:08:36 GMT

Ok, so I had a chance to play with Zebralight H600, and it is a great flashlight (and great gift from my great girlfriend). Unlike Petzl Nao, it is small enough to fit under the helmet, so that you can actually use it for riding. Ouch, and packing is also way nicer than Petzl; simple cardboard box, not bloated paper box including paper and embedded magnets, with big sticker touting how environmentaly friendly it is. Zebralight is actually friendly, Nao just claims so.

So far so good. I actually like this flashlight. Now... the blinding part. This beast has 750lm, in pretty small package. Activated by single short click. The battery contacts had some problems for me, I tried to troubleshoot, and of course I got "hit" by 750lm beam from close distance. (Fortunately not by the center of the beam). Results are not nice.

Perhaps short click should activate the lowest mode? Or perhaps... when going to the highest setting, it should turn on the power gradually, so that eyes have chance to get evasive action?

Single short click while the light is on turns it off. That is nice; no clicking through other modes (including high-power) when turning of Nao.

Now, normal 18650 fit into the Zebralight. (Good, no custom accumulator as in Nao case). I got dx (sku 5776) TrustFire Protected 18650 Lithium Battery 2400mAh, and dx (sku 47499) Universal AC Charger for AA/AAA/6F22/18650 Battery (AC 100~240V/EU Plug) charger. Despite advertising EU plug, charger will not actually fit into EU socket, but that can be worked around... batteries work as expected, and they are protected. Which is actually bad bad thing.

So.. primary use for the headlight is horseback riding... and for that I need light that stays on. 0.1 lumen is okay (actually, sometimes it is too much, but it is still way better than 10+ minimum mode on Nao), but you need some light so that a) hunters don't shoot you b) cars don't hit you and c) you don't hit any branches.

Nao tried to scare up my horse by doing three bright flashes when battery went low in low-power mode. (Successfully). But then it kept shining... and when the battery went really low, it kept shining without ability to turn it off. Not nice, but that one did not try to get me killed (well except for trying to convince me to ride without the helmet).

Zebralight is another story. So far testing was done at home, battery lasts about 110 minutes in 420lm mode, then goes to 21lm mode for 10 minutes, then goes to lowest mode (0.1lm). It gets hot (as in "too hot to touch") in the first part of the test, and I was not even running it in 750lm mode for more than 6 minutes. But the bigger problem is behaviour at the end of cycle.

Single click activates high-power mode; but the battery can not support high power mode, so current is quickly limited. So far so good. But do it few times (and it is very easy to do by mistake), and current limiter fails to limit it quickly enough, tripping the protection in the battery. At that point, battery has 0V, and you are alone in the dark. Say hello to cars and branches, and try not to look like a pig.... (You can't blame the battery; it is down to 2.8V at this point).

Zebralight is great flashlight... but not going to full power mode on short click (or some other way of improving low-battery behaviour; it already has CPU and knows battery is low, perhaps it could limit to lower-power modes from that point to battery removal?) would make it even better. (How do I update its firmware?)

ALZA: great deal on 1000mAh batteries

Fri, 18 Jan 2013 20:50:54 GMT

ALZA had two AAA, NiMH, 1000mAh batteries left, for a great price. And yes, I was stupid enough to buy them. Unfortunately, NiMH batteries do not have manufacturing date on them, but I guess they were old. ... Charger showed only <150mAh capacity. 600mAh batteries from same store, same day actually had ~600mAh reported. Oh well, will have to return them I guess.

At least Li-ION batteries from DX seem to work... it would be harder to return those.

Desktop PC troubles

Sat, 05 Jan 2013 21:16:25 GMT

Desktop PC was giving us troubles for like half a year. It seemed centered around graphics card (failed to POST, VGA card fail, crashes at runtime), but it did have some memory problems too (hard to reproduce; overnight gcc was ok, overnight memtester was not, with single-bit problems). Today Lenka worked with DVDs a bit, and result was crashes "a bit too often". That looked like a clue, so I tried disconnecting some hard drives. (This machine had 4 hdds + DVD RW)... and that helped. PC is now powered by two power supplies (400W + 300W), and I believe problem is solved. Next step is probably getting 2TB drive...

Morale of the story? Yes, power problems are easy to trigger in PCs, and no, power supply is not clever enough to shut down.

Getting number of unread sms on maemo

Fri, 28 Dec 2012 00:07:43 GMT

...does not seem to be exactly easy task. Best way I could figure is using sqlite on /home/user/.rtcom-eventlogger/el-v1.db (thanks to Kurt Fleisch). I really really miss sl4a-like interface... So much that I'm creating android.py to run on maemo.

Night riding (and Petzl Nao review)

Thu, 27 Dec 2012 18:51:06 GMT

Okay... so I like to ride my horse at night. I modded few headlights in past, and found that I sometimes like to use _very_ low power levels. Like 10uW (That's 0.001 lumen IIRC), because they preserve night vision, don't annoy people around me too badly. I even put a headlamp on a horse... it worked, but then I realized that it may not be so good idea. Now... my girlfried gave me Petzl Nao (big thanks to her). It is beatiful, feedback-control is actually very nice. But... it does not really have low power modes, and does not fit under helmet. My horse says I need to wear a helmet (6yr old fjord). I tried setting it up on the computer (and control software is slow with bad user agreements), but even lowest setting is way too high -- and that would not help with helmet issue, anyway. So I'm getting something new, Zebralight H600F should be on its way, 700lumen max and 0.1 min.

Nao low-battery behaviour leaves something to be desired. You have light on lowest setting to preserve power, and then got hit by three unexpected, very bright flashes. I did not like that, and nor did the horse. Ouch and when battery goes _really_ low, it still shines (good), but can't be turned off (odd).

And a bonus horse in Berlin's subway story.

Cheaper is not always better

Thu, 13 Dec 2012 19:36:37 GMT

Cheaper and more effective patents in EU. Altrough "cheaper" may sound like better... that's not the case here. It is more like "cheaper and more effective weapons of mass destruction" :-(.

Headlamp that reacts to its surroundings -- finally

Sun, 09 Dec 2012 11:21:20 GMT

I thought about building this some time ago... and I'm glad Petzl finally did it: headlamp that limits power when you point it to something near, such as map. Petzl Nao seems to be interesting piece of hardware. I'm not sure if they are capable of modes I'd include... I'd include 1 micro-W mode, useful for walking in the forest with eyes adjusted to the darkness, still good enough so that branches do not hit you in the eye. And I found that cca 10mW mode, where you can approximately see meter or two before you and still keep some night vision is useful, too. In general, "put out as much light as you can without affecting night vision" would be cool, but I'm not sure if that's easy with current hw.

Decoding oops pictures

Thu, 29 Nov 2012 21:14:27 GMT

Should be fairly easy... But normal OCRs are designed to recognize printed text, not VGA font, so I'm not surprised they fail. However, if we know the font used, recognition should be simple. (Bad debian and their non-standard font...). Everything could be probably helped by having something like "XXXXXXXX" line at the top of oops so that decoder could calibrate itself. Or maybe existing parentheses around addresses could be used. Would it be enough to decode just the numbers?

n900 camera cover mystery

Mon, 12 Nov 2012 00:47:28 GMT

Camera in my n900 stopped working ... "Open lens cover", but opening it did not help. I removed the back cover, and voila, camera works. Then I seen loose piece of metal, and figured that it probably causes it.

Today I studied lens cover in greater detail, and appears to use optical sensor to tell if lens is closed or not. "Lens always open" is better failure then "lens always closed", so I put a piece of paper in there. Optical sensor should be blocked now. Weird thing is that camera cover now works, reliably as far as I can tell. It somehow detects the cover through the piece of paper. I wonder what kind of magical x-rays it uses...