Author Archives: Paul

Use SPI port on raspberry PI

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SPI is a frequent way to interface slave device with a micro-controller / cpu. SPI is a 4 wires synchronous connection between a slave and a master. As part of the 4 wires, there is a CLK signal, the speed is not defined and depends on the slave but it is usually > 10Mhz. SPI allows fast data transfer. Two data signals (MISO and MOSI) for Master (In/Out) Slave (In/Out) are used to transfer data in sync with the CLK clock. The last wire is a chip select signal named CEx for Chip Enable. As you can manage multiple slave, you have to manage different CEx signal, one per slave.

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Do you know sigfox ?

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SigFox is a French radio frequency technology allowing a really low cost data transfer from Machine to Machine. Compared to GSM, this solution have some great advantages : it costs only 10-16€ per year and the energy consumption is about 1000 time less. For sure there is some constraint and the main one is the quantity of information you can transmit. In fact you have a limit of 150 sent messages / days with a length of 12Bytes. It’s not big but is it enough for a lot of IoT and M2M applications.

This technology works as a modem you can connect to any platform like Arduino, RaspberryPi. The chips are provided by TelecomDesign from a cost about 15€. The starter kit is about 150€ here.

The great advantage of this technology, in a operator point of view is the low density of the architecture where you need only 1000 antennas to cover a territory like France. As a consequence, at this time, already 90% of the country is covered by this technology.

Create a controlled 12V output for Raspberry Pi

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I had to add a 12V controlled output for my raspberry Pi to connect a radio frequency system to my Pi. This system just need 12V to start transmitting but it needs 12V ! The raspberry can offer 5V or 3.3V. The solution is to use a currant elevator system. The one I built is based on a Texas Instrument component TPS6734, able to deliver 120mA / 12V with a 3.3V input.

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My talk about Internet Of Things on Santa Clauss

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Last year in December, I gave a talk on Internet of Things, here is the youtube video (in French) – The slide are also here : http://slid.es/disk91/internetofthings

Getting start with rfrpi card v1.0 – rf433 for raspberry pi

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rfrpi_2RfRpi card is a RF433 emitter and receiver add-on of Raspberry Pi. This card is based on high quality receiver and transmitter I have selected after tests you can find here and here. This article describes how to get start with this shield.

To buy this shield the best way is to sent me a comment on this post, the price is 60€

The Shield is now working with Raspberry PI B+ and previous versions. The Shield is also working with Raspberry PI 2+. For these two last version you need to compile a kernel driver.

 

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Eclipse IoT in Grenoble

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Yesterday, I was in Grenoble for the Eclipse IoT days. It was a great opportunity to listen and learn from some actors of the IoT movement. The day was on the campus where we have been invited to see some student work on home automation and robotic for telepresence (see my twitter photo feed). The day was intensive on conferences with the really good quality and interest.

Most of the discussions / demonstrations were based on Home Automation, Smart house and globally telemetry. Not many industrial applications has been shown but some of the companies are working on industrial domain. Most of what has been shown is applicable on industry.

All the project are separating sensors, based on low cost / low energy devices associated to a local management/administration platform connected to Internet. The technology in use are mostly :

– RF and ZigBee for sensor to management platform

– Java for the management platform running the OSGi platform (Java) (this is also due to the fact Eclipse were organizing the conference and OSGi is Eclipse framework) This OSGi framework integrates management tools to connect / upgrade the platform remotely.

– Mqtt to communicate on Internet

– A custom MDM solution is deployed to manage the platforms (generally based on server management solution instead of MDM solutions) like roboconf.

Regarding the different architectures, some maintain the data on site with a in-house user interface, some export data outside on “cloud”  with an on-Internet user interface. As much as I’ve seen the in-house strategy is largely loosing on performance and interface quality due to the limited power of the management platform to perform advanced HTML experience. I assume this is also related to the Java choice to run these applications.

The other interesting learning is that most of the companies are using Raspberry Pi and Arduino to prototype solutions before, I assume, building a more robust platforms. Opensource is also mainly used and presented as the only solution to make the IoT market based on standard to be integrated all-together.

Control a high power circuit with arduino

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irf9540I had to control power on an external circuit using an Arduino. the objective was to delay the power-on of a device consuming about 3A. One of the solution is to use a relay but it is a quite expensive solution another one is to use a Mosfet. This is the solution I’ll describe here.

 

 

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making a 5V – 3/4 A power supply for car

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car_alimFor one of my project, I needed to have a >3A power supply to put in my car, delivering stable 5V. For this I tried different power supply from ebay used for phone & tablets. One of them was not so bad if you connect it after engine start. The main issue with these power supply is the poor quality of the filtering and engine start spike cancellation. As my circuit is sensitive to this spike, I decided to build my own power supply.

Here is the summary of this experience … click next !

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