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 …

I2C activation on raspberry PI B+ and 2

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The new version of kernel now activate the device-tree standard, it means that instead of having all module activated by default with some stopped by a blacklist system, now, all are disable and activated only when described in a device tree.

Device tree details the system architecture and dependencies following configuration files. The device tree can be owned by the shield itself in an attached eprom.

As a consequence, now, i2c / spi are not activated by default. So if you need to activate it on startup. For this, edit /boot/config.txt and add line at the end like :

dtparam=i2c_arm=on   # for i2c 1
dtparam=i2c_vc=on    # for i2c 0
dtparam=spi=on
dtparam=i2s=on

dtparam=i2c_arm=on,i2c_vc=on

Then reboot

Add wifi to an arduino for 4€ with an ESP8266

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esp8266 wifi for arduino

esp8266 wifi for arduino

The ESP8266 is a simple standalone addon for any board that works fine with Arduino and only cost less than 4€ on ebay.

It can operate as a device or an AP can gives wireless network connectivity to your application. It is interfaced with Arduino based on a serial line. The only problem of a such thing ( as for most of wifi chip ) is the power consumption. It requires about 150mA to run ; a lot for batteries.

My Friend @couac made a really good post on how to make it working with a Yabas, basically any Arduino board, I recommand the reading of his post : william post on ESP8266

Sigfox Rf test first experience

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This morning, some colleagues helped me to test the rf performance of one of my sigfox tracker. I’m really not an RF expert, I try to improve but there still be a long way to go…

In this design I’m using a TD1204 and a Wurth smd 868 antenna ; I have a 100 ohm impedance net between both (sure it is bad) and LC circuit (that sound not to be the good one – btw).

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Design a 50 ohm impedance microstrip line for RF signals

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For RF signal you must draw a 50 ohm net between chip and antenna to get the best performance.This post is the result of my web research on this topic …

There are two ways to design your emitter to antenna solution:

  • A microstrip line : basically you have a net on the top driving the signal and a ground plane on the PCB bottom

microstrip line

  • A coplanar wave guide : your signal is drive by a PCB net on top with two ground plane area on its left & right. If you also have a ground plane on the bottom it’s a grounded coplanar wave guide

The way to get a 50 ohm communication way is different depending on your choice.

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Tobeca 3d printing settings for PLA

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After some month of use of the Tobeca printer and a lot of time spent to find the right settings, this post is summarizing my experience. I mostly worked with PLA because I was not really fan of using acetone and abs+ acetone mix on a 80°C heating plate, so I’ll not yet detail how to setup ABS, but why not later. So this post is about PLA, about temperature, about adherence and Repetier settings.

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Baku 702B soldering station – change your soldering iron head

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BAKU 702B Soldering Station

BAKU 702B Soldering Station

I wrote a post about the baku 702B 6 month ago with my initial feedback after receiving it.

After 6 months, my feedback is good and the station works well. I just made 45 raspberry shields with it using the air flow and the soldering iron and it make the job.

Now it is time to change the soldering iron head. For sure its life has been short compare to my previous one from another brand. My fear was to find a compatible head as I saw none of them with the 702B reference.

The solution is to search for 936 – 937 station or Tip 900M, they all are the same and works well with the Baku 702B. Go on ebay and pay 1/2€ each ; you will also find different head type. I recommend to order some right after buying the station as they are coming from china (generally) and your need 2-3 week to get them.

RFRPI – wiringPi delayMicrosecond problem with RPI 2+ and fix

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I fixed tonight a problem with rfrpi and Raspberry 2+ ; it seems that wiringPi 2.25 have a bug with delayMicroseconds() function that works perfectly when less than 99us and do not work correctly with larger values.

Waiting for the fix the code have been updated to work correctly with RPI2+ ; so please if you are using the shield with RPI2+, update the rfrpi code from bitbucket.