Lair Of The Multimedia Guru

December 25, 2015

Bluetooth tracking devices/tags/”key” finders battery lifetime

6 weeks ago (11th november) i switched both the tags i have on and put them in the same drawer in my kitchen, i then tried to connect to them when i remembered about it and tried to make them beep remotely. the itag failed to connect the next day but worked again after removing the battery for a moment, the day after that it failed again and no longer recovered after removing the battery (which was at 2.897V but apparently could not supply enough current anymore for the tag to power up), on last connection it showed 100% battery. Powering the itag off a bench power supply showed that it still worked fine.
Meassuring its current draw, shows 3uA when switched off, and around 1.1mA when on, considering that the tag has to be on to be of any use, that renders it useless as it eats batteries too quick.
the smart finder / “small lovely” continued working till when i tried it yesterday when a connection was no longer successfull, pushing its button it still produced a silent click which on repeated presses got weaker. so it too used up its battery after about 4-6weeks (i had last tried it 2 weeks ago when its battery was shown at 100% in bluthooths stuff).
Meassuring its current consumption, it draws 2.4uA when off, and when on after some initial higher draw fluctuates between 2.7uA and around 88 uA with an apparent average of 39uA.
Note, the current draws depend significantly on the voltage for the itag at least (i tested at about 3V), also the uA meassurements where at the edge of what my multimeter could show so they should all be considered approximate.

In summary, the itag i got eats its battery in 2 days, the smart finder thingy in about 4-6 weeks. I would have tested more tags but these where the only 2 i received. another one i ordered off ebay was lost in shipping apparently

Filed under: Electronics,Off Topic — Michael @ 23:20

November 27, 2015

Modifying a 80-250V AC Volt/Amp/Power meter to make it work for 0-250V AC

A while ago i bought an old variac on ebay, it was in good shape but lacked any meter, originally that model had a analog voltmeter or something. That was missing, some cut wires sticking out of where it was. As i got it it also had a 6.5Amp fuse in a fuse holder marked as 4A and its output wires connected straight bypassing the fuse.
When i bought it my plan was to stick a cheap digital meter to it, which is what i did and also a modern and correct “fuse”.
IMG_0395-1280
The meter i found and got supported 80-250VAC, i failed to find one supporting AC voltages down to 0V. I originally had not planed to modify it, as it didnt seem a big issue, but it was just annoying that around 70V it dropped out and displayed junk and then went dark.
IMG_0397-1280
Inside it looks like this:
IMG_0398-1280IMG_0399-1280
I saw 2 obvious ways to make this work with lower voltages, first is to make its AC->5vdc supply work with a wider range of AC voltages, the other is to split the voltage sensing off the supply. As my variac provides around 250VAC in addition to the variable and isolated output, using that seemed to be the easier solution.
But before i continue, a warning, do NOT try this unless you understand what you are doing, mains voltage can be dangerous and can injure or kill. Also not all similar looking such meters are neccessary identical and this modification might result in undefined behaviour in that case.
The voltage is sensed through R3 which is 1Mohm, removing it:
IMG_0400-1280
Results in a working amp meter with 0V:
IMG_0401-1280
Next we need an additional connector for the separate AC power and AC sense input, to get that we just need to clear 2 from solder and cut the 2 connected pins on the other side using a file. Note, if you try this modification double check that the new freed up pin is not connected to anything else by some tracks below, it wasnt in the meter i had but that doesnt imply its not in yours.
IMG_0403-1280
Now its tempting to use the same or a new 1meg ohm resistor for the new sense wire added below (and i did and it worked) but this is probably not safe, first you should clear the conductive parts of the logo which are below, off the board and use 2 resistors in series as there is about 230VAC over it, yes it was already before any modifications but still.
IMG_0405-1280
IMG_0416-1280
You can also slightly adjust the value of this resistor to adjust/finetune the volt-meter.
The other side of the resistor is connected with a mod wire to the newly freed up pin on the other side. Again using a file to make some cut in the board to nicely route the wire around.
IMG_0408-1280
The new connector is then connected like this:

  1. Variac secondary tap 1
  2. Variac secondary tap 2 and Load/Output connection A
  3. Variac secondary tap 3
  4. Load/Output connection B

Testing, works:
IMG_0412-1280

Filed under: Electronics,Hardware,Off Topic — Michael @ 0:11

November 9, 2015

Bluetooth tracking devices/tags/”key” finders

A while ago in coverity while fixing FFmpeg bugs there was a some kind of Nominate a bug, win a prize thing, i didnt ever nominate one but this was when i learned about the existence of tile which would have been the prize one could win. A BLE device that can be attached to something valuable and that can then be searched and found with a recent android or iPhone, or the other way around using the device to find your phone.
This seemed potentially useful to me, though i personally have never lost my keys or phone for more than a few seconds, i know someone who does have that problem. So i thought buy a tile or 2 they might come in handy for something but then i saw the price, non replaceable, non rechargable battery and thought ok, didnt expect someone would be that lame. I guess one should not expect any company not to attempt to rip its customers off to the maximum extend possible.

Lucky there are many similar devices, so the goal was to find the cheapest that works and is not just tied to a ridiculous business model. So i bought some of the cheapest i could find (they of course all have user replaceable batteries …)
First is something that identifies itself as

ITAG

IMG_0383-1280IMG_0384-1280
The above one is one example of these, they come in many different shapes, cost less than 5$ with free shipping. The first i got had a different shape and came with a dead battery and also ate a new battery within a day. The second i got is the one pictured above, which worked more or less.
When Off, A long press on its large surface switches it on with 2 beeps.
When On or connected a long press switches it off with a long beep (this renders it useless as its easy to press by mistake)
When on but not connected its led also continuously blinks, draining the battery but making finding easier, it also at least once hanged and required the battery to be disconnected for a moment to function again.
On the BT protocol side setting immedeate alert to 2 results in 30 beeps and led blinks, setting link loss to 0 or 2 has no effect, the device always beeps on unintentional connection losses as far as i could figure out. pressing the button results in a notify with value 0x01 on 0000ffe0-0000-1000-8000-00805f9b34fb / 0000ffe1-0000-1000-8000-00805f9b34fb.
To make the itag only blink and not beep on immedeate alert, 0000fff0-0000-1000-8000-00805f9b34fb/0000fff1-0000-1000-8000-00805f9b34fb can be set to 0x00, this is remembered over disconnects but not over switching the tag off. All other values seem to cause blinking and beeping.
To identify it this may be helpfull:

  • 0x2A29: CEVA
  • 0x2A24: BT 4.0
  • 0x2A25: 12x07x2012
  • 0x2A27: SM-1
  • 0x2A50: Bluetooth SIG Company: Ceva, Inc. (formerly Parthus Technologies, Inc.)
    Product Id:13330
    Product Version: 26369

Smart Finder

IMG_0380-1280IMG_0386-1280
The above is another sub 5$ tag, which appears identical (minus the logos) to tags on amazon from chirotronix and ikee.
The official software for android (“small lovely”) has a rather long list of unneeded permissions like for the previous tag (“iTracing”) but for this theres also no inofficial sw i could find for android which supports these tags, which is why i reverse engeneered the protocol
When off a long press switches it on with a long beep, to switch it off again 5 rapid short presses are needed (resulting in 3 beeps).
When in On mode pressing the button results in 2 beeps this also causes the “#255 Manufacturer Specific Data” to change from 0x58,0x48,0x52 to 0x58,0x48,0xFF for a few seconds, apparently to identify which of potential several devices one wants to connect to. Switching the device off also seems not possible while it is connected. On connect and disconnect its led flashes once.
Protocol wise neither “link loss” nor “immedeate alert” have any effect that i could identify. To make the device beep and blink a command must be written to 0000fff0-0000-1000-8000-00805f9b34fb / 0000fff1-0000-1000-8000-00805f9b34fb. A single 0xAA results in some short beeps and blinking. Its also possible to write a 5 byte command 0xAA 0x03 count duration1 duration2. The count is the number of beeps, the 2 durations are the beep and non beep durations in milli seconds, i dont know what the 0x03 does or if there are other interesting commands.
To detect button presses the device can send notifies on 0000fff0-0000-1000-8000-00805f9b34fb / 0000fff1-0000-1000-8000-00805f9b34fb with a 3 byte value, it is either (0x01 xx 0x00) xx = number of short button presses or (0x02 0x00 xx) xx = number of seconds button is hold
To identify it this may be helpfull:

  • 0x2A29: SIGNAL
  • 0x2A24: BT A8105
  • 0x2A25: 00001
  • 0x2A26: F4F5V02
  • 0x2A27: A8105F4
  • 0x2A28: 1030627

The name of teh device is “AMIYJ_5B68”, i dont know if this is true for all these devices, google seemed not to have any hits on that.
It seems using a A8105, (the ITAG seems using a BK3431) datasheets can be found with google.
Interestingly theres also a entry for “Heart rate” on the bluetooth level, so i guess this shares some code with some other devices.

IMG_0382-1280

Hope something above is useful to someone

Update: 2015-11-09: corrected itags link loss behavior
Update: 2015-11-10: Added names of the official apps
Update: 2015-11-14: Added itag blink only info (found by and thanks to Joachim Schäfer)

Filed under: Electronics,Hardware,Off Topic,Reverse Engineering — Michael @ 3:16

July 7, 2014

Toothbrush

Its quite a while since ive updated my blog, and indeed ive a few things i wanted to put up but have always had something more important to do, well. Today, ive finally decided to skip doing important things and put up something really unimportant.
A while ago I was reading the manual of a toothbrush, an electric ehm “sonic” toothbrush. It said something like 40000 revolutions per second. Reading that and looking at the humble, el-cheapo toohbrush i didnt belive it, so i had to find out how fast the thing vibrates (it actually doesnt do full revolutions). Using my soundcard was out of question as that wouldnt work above 24khz. So i used a old analoge osciloscope that i got for 15 euro from a local flea market a while before.
IMG_4563small
You can see on the scope, the vibration of the toothbrush head as well as a 1khz reference square wave. The trick is that the toothbrush head is made of some kind of plastic and by rubbing it against something, it becomes electrostatically charged. Just holding the scope probe near then shows the movement of the head.
We can see on this that in about 6 cycles of the 1khz signal we have 2 cycles of the toothbrush, which would give ~1000/3 hz.
Which is 120 times off from 40000, if one considers both ends of the vibration instead of a full cycle its 60 times off. And at that point i looked at the manual again and realized it said 40000 U/min not sec :)
Which proofs my way of measuring it is quite spot on, but my way of reading the manual isnt.

Filed under: Off Topic — Michael @ 4:23

January 16, 2014

Rant about gmx

Ive been using gmx since over 12 years for my email. And until recently gmx did a fine job at running a SMTP and a POP3 server. But it appears this is slowly changing. A few month ago their SMTP server stoped accepting mail with the verbose message: “550-Requested action not taken: mailbox unavailable\n550 Reject due to policy restrictions.”. It turned out that gmx refused localhost as domain to the EHLO SMTP command. They require a fully qualified domain name now right? no, not really, any random string seems to work just not localhost. My attempt to contact gmx about this, lead to no reaction.

The next thing was this: “550-Requested action not taken: mailbox unavailable\n550 invalid DNS A/AAAA resource record”, yes thats right, gmx rejected outgoing mail because the poor guy had not set up a webpage on the domain that he used to receive mail on. This one btw affected multiple people i tried to communicate with, not just one.

But hang on it was just starting, next there was “451 Requested action aborted: local error in processing’ errormsg=’recipient address nicolas george normalesup org not accepted by the server”

Also it has to mentioned that gmx at around that time (maybe 1-2 month before or so) started to randomly put “*** GMX Spamverdacht ***” in the subjects of random received mails even though i always had and have all spam filtering disabled at gmx (mainly because their filters never worked).
So yeah another try at complaining to gmx about that, and yes this time there was a reaction, i got a mail from them “GMX Sicherheit: Vorsorgliche Sicherheitssperre Ihres GMX Postfachs!” they locked my account and provided me with a few tips on how i can scan my windows system for viruses. Hello gmx, i dont use windows.

My next attempt to contact them and now find out why they locked my account lead to just a polite (probably automated) mail with a link to their payed and expensive phone support. Seriously, locking someones account and refusing to tell them why unless they pay. And locked btw means SMTP was not working, POP3 still worked and so did the web interface where one is asked to change ones password which then unlocks the account again. Maybe iam just missing the point but what sense does that have.

Was that all? no, it seems gmx also reduced the maximum size of mails as a 21mb mail i tried to send to 3 people could not be sent over gmxs smtp server and with a different smtp server it bounced from reimar who also uses gmx so it also could not be received. Iam pretty sure i did transfer bigger things years ago.
Ahh and i almost forgot: “5.7.1 : Recipient address rejected: Your MTA is listed in too many DNSBLs; check http://www.robtex.com/rbl/82.165.159.40.html”, Yes thats gmx being in the DNSBL lists at the time that happened. Now just why was i not surprised by that …

Did anyone really read this far down ? Well as gmx slowly goes from well working to something else, iam forced to find alternatives to handle email. So i got this one: michael@niedermayer.cc, iam still using the gmx addy though, feel free to use either if you want to mail or spam me. I guess if these issues with gmx continue then ill have to start updating my mail address everywhere …

2014-01-26 Update

Heres an example of the random marking of mails as spam, the 2 mails where simple git patches send to ffmpeg-devel, sent by me, at the same time from the same computer and their content should be quite similar and should not have triggered any properly trained bayesian filter.

85260 N 0126 2:11 Ronald S. Bultj (1.3K) [FFmpeg-devel] [PATCH] vp9: disable use_last_frame_mvs on resolution change (scalable).
85261 N 0126 2:30 Ronald S. Bultj (8.9K) [FFmpeg-devel] [PATCH] vp9: fix invalid ref frame w/h on size change.
85262 N F 0126 14:49 To FFmpeg devel (1.2K) [FFmpeg-devel] [PATCH 1/2] avcodec/libfdk-aacenc: change MODE_7_1_REAR_SURROUND to map to AV_CH_LAYOUT_7POINT1
85263 N F 0126 14:49 To FFmpeg devel (0.9K) ??>*** GMX Spamverdacht *** [FFmpeg-devel] [PATCH 2/2] avcodec/libfdk-aacenc: change MODE_7_1_FRONT_CENTER to map to AV_CH_LAYOUT_7POINT1_WIDE_BACK

Also ive sent gmx a link to the blogpost, no reaction from them so far

Filed under: Off Topic — Michael @ 4:33

January 12, 2011

Unidentified flying insect

I found 2 Insects looking like this in my appartment:

Anyone knows what it is, its about 10cm large from leg tip to tip if it stretches out and capable of flight, seems not to have any inteligence to speak of. I could catch it and throw it out of my appartment but iam affraid its too cold outside?

Anyone knows what it eats? How long it lives?

Filed under: Nature,Off Topic,Pictures — Michael @ 3:52

May 1, 2010

Modern notebooks

My acer NB today: Critical temperature reached (101 C), shutting down.
And disablng power management of the HD produces errors after a while, not just today but always.

Filed under: Hardware,Off Topic — Michael @ 18:57

April 14, 2010

“Latest” firefox

A little rant to keep my blog from rotting, firefox after 3.0 or so no longer works on kernels that randomize memory allocation a bit. Ones choices are either patching firefox or to disable the randomization for it. And we all know if one application needs all the security layers one can get then its the modern web browsers.
Not to mention how one can be so lame to have such bug open for ages and still not even produce an error message but rather run mmap() munmap() in an infinite loop.

Filed under: Off Topic — Michael @ 21:14

October 28, 2008

Pizza

As the little reverse engeneering puzzle has been solved, we need some prize …

img_2801pp.jpg

flour, olive oil, half a teaspoon sugar, dry yeast and water. No thats not yet the price ^^; And probably not even a half correct pizza dough but i like it and am too lazy to look up what is “correct”.

img_2815pp.jpg

After rescaling the x,y and z transformation vectors of the dough it becoms flat and roun hmm square?! (… i guess ill file a bugreport about that one later) adding tomato puree and tuna.

img_2818pp.jpg

Adding gouda cheese and oregano, i should probably have added more cheese but transforming a block of cheese into these stripes is boring and the ready made pizza cheese from supermarket could be more accurately be described by milk+yellow color and thickening agent so that stuff was not an option.

img_2824pp.jpg

After ~15min at ~493 kelvin

And at last, the pizza was turned into a virtual pizza, which i herein officially give to chrono! The real counterpart has for saftey reasons been quickly ea ehm i mean destroyed, to avoid paradoxes.

Filed under: Cooking,Off Topic,Pictures — Michael @ 0:18

January 4, 2008

New Years Eve Fireworks

Random pictures from around midnight 2007-12-31 / 2008-01-01. Downscaled a little so wordpress autogenerates thumbnails and doesnt randomly refuse the uploads

img_2388-med.jpgimg_2418-med.jpgimg_2449-med.jpg
img_2486-med.jpgimg_2497-med.jpgimg_2517-med.jpg
img_2525-med.jpgimg_2533-med.jpgimg_2535-med.jpg
img_2540-med.jpgimg_2555-med.jpgimg_2571-med.jpg

Filed under: Off Topic,Pictures — Michael @ 1:43
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