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 …

GPS antenna comparison

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antennaI’m using different GPS antennas with different price, size and gain and I had never compared the result in a real live test. So now it is done and the result are good to share.

My test condition are quite bad and we can’t really consider this as a scientific bench but, experimentally it sounds like a real life test.

So the test is to connect an antenna to a TD1204 with a GPS code on it and test the time it makes to fix the position and get some note about signal level, satellites in view… I used in fact 2 TD1204 : one with a reference antenna to ensure we have equivalent condition from one test to the others. The tests are made indoor where the sensitivity is an important factor. This post detail the results.

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Smart Everything Sigfox board

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capture-decran-2016-10-14-a-21-14-03I have recently discovered the smartEverything prototyping board for Sigfox. This board was used during the SigFox maker tour and It is really nice for creating some prototypes and evaluate the technology.

The board is an Arduino board based on an Atmel SAM D21 MCU (Cortex M0) with 256KB of flash and 32K SRAM running @48Mhz

The most important part is concerning the sensors available on the card and this is clearly the best point about this board : you have a lot of them available : crypto authentication chip, BLE module, GPS, NFC, Accelerometer / gyroscope / magnetometer, Pressure / Humidity / Temperature sensor, proximity light / sensor, RGB Led, Led & push button. It can be powered by USB or external 2xAA batteries.

The board cost is about 106€ and can be found at RS. It is provided with a sigfox network access to the backend.

This post detail how to get start with the board

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Have a good start with Telecom Design EFM32 starter kit

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Telecom Design kitAfter making my kit on my own, I finally got the official Telecom Design TD1204 kit (thank you TD) There is no big issues to use it once you have the right entry point, but as I had some email exchange with support to be fully ready for using it, I’m prefer to share some words with you on what to do and how it works.

Basically, the TD kit is an EFM32 Tiny Gecko Starter kit (STK3300) with some little modifications.  The EFM kit have two interesting functions : in own a Jlink JTAG/SWD programming and debugging interface and its EFM32 MCU can be use to monitor power consumption with precision.

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Access to a remote mongodb with mac OsX client

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I needed to access a mongodb instance to manage my collections. I was looking for something like phpmyadmin for mongo but the first tool I found was mongoclient.

This tool is an application for desktop provided for many OS including mac OsX. The quality of the tool is really good.

The mongodb was installed on my server remotely and protected by a firewall so the easiest way to access it was to open a ssh tunnel. Mongoclient is supposed to manage the ssh tunnel in the application but it was not working for me so I had to manually connect the tunnel :

# ssh -L 27017:localhost:27017 -p 22 user@mongodb.server.com

Once connected it is possible to create a localhost connection with mongoclient.

 

 

Update Telecom Design SDK from 5 to 6.3.4

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TD1204 / Sigfox & GPS

TD1204 / Sigfox & GPS

New version of the Telecom design SDK has been released for TD1208 / TD1208R / TD1204 and now officially supporting TD1205.

This new version provide some bug fixes, like a crash after 21285 transmissions that could be after 212 days in case of full use… some I had in touch with could be interested… @pioupiou and also a bug that disable gpio interrupt after sigfox transmission (I experimented it !)

For the main evolution, this version is supporting FCC and TD1508 and improving sigfox transmissions.

From my experience, this version is also a good way to decrease the size of your binary files.

This post is about upgrading from a SDK 5 to SDK6 and the impact you can when recompiling your projects.

To install the SDK from scratch, just follow the well documented official post here.

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Create a php function in php to receive LoraWan Objenious callback

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Lora-300x171I’m actually doing some experiment with the French LoraWan network operated by Objenious. To receive the message on your backend application, one of the way is to build a callback function to proceed the data.

Due to LoraWan protocol, you have different type of possible callback like for: joining network, uplink messages and downlink report.

This post gives an exemple on how to implement an uplink message callback handler, with php, for your application backend server.

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SigFox (LoRa) and antenna design

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antenaToday Sigfox is releasing a really good document about antenna design. This pretty document can be found following this link (available on July 7th). This document from TI also contains really well detailed information about the alchemy of antennas and the different kind of product you can find. From Silicon Labs you also have an interesting development kit for 868 antennas with performance published in this application note.

This is to say antenna is one of the most important part of a 868 object, as for Sigfox as for LoRa where the problem is basically the same. I discussed with different sigfox object designed and every-time the antenna was a big project issue. Some has payed about 10-15k€ to get a custom optimized design.

I never experiment a custom design but I made test with various antennas and the purpose of this post will be to give you my feedback on the different solutions.

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3d printing – resize an object with different factor on axes

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openscadTo tell you the full story, I was working on a 3d object I want to reproduce. The initial model is a 10cm object. I’ve got a 3D scan of this object and now I want to make a mold to reproduce it with a smaller size (3cm). All should be simple as even my printer software have a resize option.

The problem started when once resized the height of the object has became too small and the precision of the printer does not allow to have a good result. For my need it was not really important to preserve proportion on the Z axis. So I was looking for a tool able to resize an object with a different setting factor for each of the axis.

This tool exists and more over it is really useful for any STL manipulation (at least you need to be a coder) : its name is OpenSCAD. This tool is a programming language for 3D object allowing different object transformation and creation.

For my need to scale X & Y with a 0.4 factor and Z with a 0.6 factor, the following code was the solution :

scale([0.4, 0.4, 0.6]) import("Moule.stl", convexity=3);

You then just have to export as STL by clicking on STL icon and you have the result. Sounds nice, isn’t it ?!?