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 …

SpringBoot and JWT security

When creating an API you can manage a “session” with a JWT Json Web Tokens ensuring the user has login previously.

This post explains how JWT is working and how to implement it with SpringBoot using user identity stored in a Database.

This is based on a real implementation and is the sum of lots of search on Internet to make it correctly working.

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The Sigfox radio protocol

Sigfox phase decoding

Sigfox is a LPWAn communication technology and network dedicated to IoT. The specificity of this solution is related to the LPWAn caracteristics : communicating Low Power (25mW) and Wide Area (60km).

This is possible thanks to particular radio characteristics and modulation. This post will describes how it works at radio level and protocol level.

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Sigfox Radio Signal Analyzer

Sigfox just released publicly its Radio Signal Analyzer tool. This is a tool for the device & module maker to prepare the P1 certification : basically it checks the radio signal shape, power… and tell you if you are following the requirements.

The tool have to be used with the SIGFOX SDR dongle provided with the SNEK tool.

The software solution can be downloaded here : https://support.sigfox.com/downloads/sigfoxradiosignalanalyzer.iso

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SpringBoot webservices full example

SpringBoot is a really efficient framework for creating webservices and much more. For this reason I’m using it to design my backend applications.

This framework is also well referenced on Internet and many people are downloading it and using it. All of this sounds really good and you will see you can make a webservice in less than 5 minutes following the many examples existing on Internet. As usually in this kind of technology once you have made the classical HelloWorld and university classical practices you have a lot of difficulties to make your first real program coupling different simple use-cases. So As I spent a couple of hours searching solution on Internet, this post will give you a full example of a project getting data from a MongoDB instance to provide a simple webservice.

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The Sigfox Network Emulator Kit

Sigfox is a LPWA network using the free radio frequency to communicate. There radio frequencies are changing in the different zone (Europe, America, Asia…) When you are developing a device you need to test it but you are not authorized to use all these frequency from the country you are.

The Sigfox emulator is a solution for this : it allows to directly connect your device and analyze the transmission whatever the frequency you are using is. The Sigfox emulator kit is an SDR dongle with a Sigfox software for understanding, decoding the sigfox signals.

You can wire your transmitter to this receiver to not emit the signal over-the-air and legally use a non authorized frequency in your country. When you are using an authorized frequency you can simply communicate over the air.

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Posted in Non classé, sigfox | Tagged , | 2 Comments

Gcc – wrap a function in a closed archive

Here is the situation : you have a function in an archive but you do not have the source code. And you would like to change the behavior of this function or intercept the call to this function.

This is possible with gcc and the -Wl,-wrap linker options. Thanks to this option you can create a new function starting by __wrap_ followed by the function name. This function will be called instead of the original one. In the function you can decide to call the original function by using its name starting by __real_

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Kerlink LoRaWan Wirnet iFemtoCell review

LPWA networks needs antennas and gateway to receive the device communication and transfer them to a network kernel. You can take a look to my post on the LPWA network architecture for more details.

In the LoRaWan ecosystem we call the first part of this network architecture a gateway. There are different kind of gateway : The network operator gateway with a big and efficient antenna, capable to support external weather like the Kerlink IoT Station and some low costs solution you can deploy at home or within a building (indoor) to cover a local device fleet.

The Kerlink Wirenet iFemtoCell device is a such type of gateway. this post will review how to get start with it and what we can expect in term of coverage.

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The impact of putting an antenna in a box

IoT design a usually a matter of antenna as already seen in different previous blog post. Antenna performance is the assurance of your capacity to deploy your object in larger zone and a way to save energy by reducing transmission power.

As we will see, if you get a hardware component and simply put it in a box its radio behavior will be totally different as the box is impacting the transmission.

This post will practically show you the impact of a box on a device radio quality.

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Posted in Hardware, IoT | Tagged , , , | 5 Comments