Monthly Archives: February 2014

How often does an IPhone with iOS7 turn on WiFi and send Probe Requests

To look up it’s current Position Smartphones continiously send out WLAN Request to use the Responses for Positioning. The Response includes the SSID of a Access Point close by. This Information can be used to look up in a database and find out the rough position (~15 meters).
This cost a bit of energy though no that much that it would have a big impact in use batterie. And it consumes even much less energy than GPS would.

Normally this lookup happens every 10sec, 30sec, 90sec.  But since the last iOS Update iOS7 it changed fundamentally the behavior of those Lookups on the IPhone.

Experiment with active IPhone:
(time difference to next probe request in sec)
3, 8, 4, 8, 21, 9

Experiment with sleeping IPhone on table:
(time difference to next probe request in sec)
479 (~8min after turn off the screen), … (15 minutes later stilll nothing !)

Experiment with sleeping IPhone in pocket:
still nothing

With iOS7 wifi seems to by totally switched off. Or at least it doesn’t send a single probe request.
Maybe it still monitors the WiFi traffic but i was not able to check this.


How to: Capture WLAN WiFi Probe Requests on Mac with tcpdump

Simply open a Terminal and typ:

tcpdump -I -e -i en1 -s 256 type mgt subtype probe-req

where en1 is your wlan interface.

For my experiments i’m using a Alfa AWUS036NH WLAN Adapter.

Bluetooth Low Energy (BLE) on Raspberry Pi with Asus BT-400

I recently bought a Bluetooth Low Energy (BLE) USB Dongle thats compatible with Raspberry Pi.  It a Asus BT-400 and had problems to make it work. AMAZON ASUS BT-400

So here is my solution.

sudo apt-get install bluetooth bluez-utils blueman

This will install all necessary software. Than type..


The result will be something like this:
Bus 001 Device 001: ID 0000:0000 Vendor Desc.
Now you have to find the correct device. When you found it, copy the ID without colon and write it into the /sys/bus/usb/drivers/btusb/new_id. In my case it was like:

echo “0b05 17cb” >> /sys/bus/usb/drivers/btusb/new_id

or (by the way don’t copy it, write it by yourself)

echo “0b05 17cb” > /sys/bus/usb/drivers/btusb/new_id

Now we will use a tool called modprobe which allows us to load modules on our running system.

modprobe -v btusb

Almost done! Just edit the config with nano  (save= crtl+o ; quit= crtl+c)…

nano /etc/default/bluetooth

… and copy the few lines below


Restart bluetooth and you are ready to go!

sudo invoke-rc.d bluetooth restart

HowTo: Build a wardrobe under pitched roof area

My girlfriend was unlucky. Living on the attic has the drawback that we had no real wardrobe. I was totally fine with that – but i’m a man. For a girl who daily reads magazines like glamour, vogue and instyle – that is not “ACCEPTABLE”.

So she did what she always did when she what’s something from me… crying…

The only problem was that not a single wall was able to hold skews. So i had to build a scaffold/framework. In total i spent 14 € on it. This are the results:

Prepair to build the wardrobe Proof of concept wardrobe assemble construction for wardrobe skews you wardrobe german accuracy =) stress test the wardrobe Painting the wardrobe white 2nd layer of paint The wardrobe without covering