Category Archives: Hardware

Tips and test on hardware components, including hardware programming and design.
Astuce et tests de composants matériels, micro-électronique et programmation FPGA.

RF433 – different receiver in test

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I’ve just done some test on different RF433 receivers, from the classical really low cost system to some more expensive systems. The test environment was always the same : a dirty test board with lots of wire connections everywhere and an antenna made with a 17.3 cm wire. The conditions are poor but identical.

Then I move around my house and activate my alarm detector one after one and check if the system received it. Some detector are same floor, 1 floor or 2 floors distance, some are behind walls, distance vary from 5 to 20 meters in house.

The following results are the number of message received by the different receivers in this context. More you see, better it is.

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MQTT on Raspeberry PI

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MQTT (MQ Telemetry Transport) is a Message Queuing system for machine to machine communications. It allows communication of mobile systems over high latency, low bandwidth and poor quality networks. It manage communications over TCP (not over Http) to optimize the size of messages and it manages different quality of services. Depending of it, messages can be dropped, received multiple times of you can have the insurance to receive the message one and only one time.

It makes this protocol really interesting for the communication between a raspberry PI and a server when this communication is event driven and the communication link looks like a Edge/3G channel.

Mosquitto is an open source implementation for MQTT.

Here are some tips on how I implemented it, for a demonstration purpose

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Arduino and hc-05 bluetooth shield

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Tonight, I start working on a third project I have in my hack list for the moment, this one is based on bluetooth and I order some arduino stuff to make it live. The arduino itself is a leonardo and the bluetooth is a hc-05 attached to a larger shield to be connected with arduino board directly.

This article details how to use HC-05 to transfer data between arduino &  mobile device based on Bluetooth. It includes HC05 source code for pairing and communicating.

Click on link to get more

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Raspberry PI – receive 433Mhz radio signal

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Tonight, the hack objective is to communicate with 433Mhz equipments using Raspberry PI. For this, I use a 433Mhz receiver from Itead Studio bought at hack spark for 4.5€ with an emitter. Cabling is simple : VDD on 5V (I tryed to use 3.3V supply voltage but as a consequence the reception range is limited to a couple of cm) , GND goes to GND and One of the data pin going to pin 13 (gpio21/27). This is following elements found on that site : ninjablocks

If you are looking for a RF433 shield for Raspberry, check this link to another article !

The first step is to install a fresh wheezy raspbian environment and get the basis element to work :

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BeagleBone Black temperature sensor

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Here is a quick hack to interface a temperature sensor to a BeagleBone Black unit.

I choose to use a Microship TCN75AVOA component. This SMS component is not really easy to use for prototyping but feasible. This component have a unit cost < 1€ and operate at 5V or 3.3V (as for BeagleBone). A Dip8 version exists. The communication with the CPU is numerical based on a two wire connection type I2C. It measures from -40°C to +125°C on 8b + 4b decimal with +/- 1°C precision.

Read next :

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Raspberry PI – wan emulation

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piwan.org

piwan.org

PIWan project : Here is a new, quick & dirty project to be done with a raspberry PI : At work we currently have to simulate our application for a worldwide usage. We have really great tools for that but they need expertise and specific campaigns. The purpose of this document is to describe a RPI based solution with two Ethernet cards and some clever command lines to simulate a wan network for developers. The advantage of this solution will be to cost less than 100euros and will be easy to use with the right documentation.

See next pages for implementation details:

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