RaspberryPi inputs: to poll or to interrupt?

One of the best features of the RaspberryPi is the GPIO (General Purpose Inputs & Outputs).

Reading the input levels on the GPIO is pretty easy, especially using Gordon's wiringPi library.

But you need to think carefully about how best to do this in the software for your chosen project.

RaspberryPi Web server: GPIO access

Controlling the RaspberryPi GPIO remotely, over a network or across the internet, seems like an interesting trick.

I copied some code from the net and gave it a try, but unfortunately it didn't want to play.

So I went back to basics and created my own simple test routine.

RaspberryPi + DS18B20 Temperature Sensor

The DS18B20 is a low cost, simple to use, 1-wire temperature sensor which is ideally suited for use with the Raspberry Pi.

Up to 10 of these sensors can be wired in parallel to a single Raspberry Pi GPIO pin, each giving a reasonably accurate indication of temperature.

The current Raspbian image includes support for these devices, so its quite easy to get them up and running.

The Linux /sys Directory & the ASUS Backlight

The /sys directory is a bit like the /proc virtual file system which I discussed in my last post.

Continuing the "everything is a file" approach, the /sys directory gives you access to many system components and their parameters.

My prime consideration is whether I can control the display backlight on my laptop.

The Linux /proc directory

Within the Linux file system there is an unusual directory.

It contains apparently empty (0 bytes) files, and includes several numbered sub-directories.

So what's that all about?

A Better "Automatic Light" Controller

This may be one of the most ridiculus, unnecessary projects I've ever got involved with.

But sometimes when an idea takes hold, it becomes difficult to shake off.

The idea is to calculate sunset using a SINE function, and use this as the basis for controlling an outside light!

RaspberryPi Webserver: install & configure

The low power consumption of the RaspberryPi means that it wont run up a huge electricity bill if left on all the time.

So its a good candidate for a webserver, either as part of your home automation system, or just for experimentation.

This post describes how I configured a Raspberry Pi using a light-weight web server application.

Pi-Mote + RaspberryPi: checking the range

The RaspberryPi fitted with a Pi-Mote controller is a neat 433MHz remote control solution for switching mains powered equipment.

But to be of any use, the operation range must be sufficient to satisfy the requirements of your application.

So I set about doing a few range tests and have detailed my method and results here.

The Pi-Mote 433MHz control unit for the RaspberryPi

This controller allows a user to remotely control power sockets via a simple program.

Having just received my kit from Energenie, this post is basically an introduction to using the system, driven by a Gambas program.

I've also included information on the serial data format, which was captured using the method described in an earlier post.