Category Archives: Technology

Tips and test on technological product and components. Operating system, networks, hardware, security…
Astuces et tests autour de produits et composants technologiques, systèmes, réseaux, hardware, sécurité …

BlueTooth BLE on iOS and Mac OsX

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The RfDuino arduino device i’m actually hacking is a bluetooth 4 (BLE) device. I was expecting to work with it as any bluetooth devices in a terminal session like with rfcomm in previous version of bluetooth.

In fact not ! BLE are not pairable as the classical BT device, they are discovered by the application itself. Then you have communication channel you can read or write to communicate.

Thanks to a post in a forum, I’ve found a really usefull tool lightblue allowing to connect any BLE device and send it data. This soft works on iOS and MacOsX.

You can also get Apple tool : Bluetooth explorer and Packet Logger here.

Control WS2812b panel current consumption

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With the 16×16 123RGB panel base on WS2812b, I have 256leds able to consume up to 50mA each. I want to use this with a limited current under 3A and want to ensure using software, this limit will not be reached. This article detailed my code for doing this.

Each led value is stored in a int array where each value is containing rvb values.

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WS2812b leds current consumption

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As described in a previous article, I’m investigating ws2812b leds provided with RGB123 board. These leds are providing a lot of light, which is a good thing but also require large power supply to light them on. As in my system, I want to control power to not overload the battery, I’m tring to predict current need and limit it.

In fact, the final equation is really easy to get. According to my different measures, the current is really linear for each of the color, equal for each of them too.

As a consequence, the final current estimate is :

I(mA) = 1 + R/16 + G/16 + B/16

Fix OpenStack / RDO / Havanna network

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After installing openstack on CentOS with RDO package (installation I recommand as it is really easy) I had some issue with network : the bridges were not connected to the physical network and well configured so I was not able to communicate with any VM created.

Here is how I solved this issue …

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Raspberry PI RF433 transmitter shield

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A lot of you are coming to my blog for RF433 with Raspberry PI content (here). This article is a small part of a larger project I have. As part of this project I built a Raspberry Pi shield including an RF433 emitter and receiver. I could sell this shield to some of view if it make interest to you. To make it I selected emitters and receivers to get the best quality / price compromise.  (read my other articles on this topic) I could sell it around 60€ + port.

Update : chek this article for all informations on the shield and buy it !

RF433 shield for Raspberry PI

RF433 shield for Raspberry PI v0.1

 

 

 

 

 

 

 

 

 

 

 

My question to you is : would you be interested in a such thing ?

If yes : leave me a comment with your email address ( I’ll will remove this address before validating it )

RF433 Raspberry PI shield v1.0

RF433 Raspberry PI shield v1.0

 

Here is the Version 1.0 with antenna connector integrated to PCB.

Problem with nvidia raid and grub2

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It’s not the first time I have some trouble to setup grub2 correctly with my nvidia raid system (also called fake-raid) … I did not find exactly why, but for sure i never try to install grub2 correctly from yast or in manual mode.

The first solution to find was : how to boot a fresh installed system when the bootloader has not been configured. The solution is here : http://www.supergrubdisk.org. This tool is really simple and so efficient to boot !  I recommend to have this in your linux emergency kit !

The second solution, once the system has start is to reinstall a bootloader. Here, in fact the solution is easy : destroy this f**** grub2 and replace it by the legacy really good grub ! lol

Then it works … last step to me: understand why gnome is taking so long to start ?!? or the answer is in the question …

I love Linux !