December 14, 2012 AT 3:00 pm

Raspberry Pi GPIO Web Control #piday #raspberrypi @Raspberry_Pi

Inspired by “Reading Analogue Sensors with One GPIO Pin“, Sebastian Bub rolled this approach into a project of his own, “Raspberry Pi GPIO Web Control,” a lightweight Java-based web application to control the GPIO ports.

From his BitBucket.org project description:

A Java webapp to control your GPIO ports of the Raspberry Pi using http.

What is raspberry-pi-gpio-web-control?

raspberry-pi-gpio-web-control is a lightweight java based web application to control your GPIO ports of your Raspberry Pi over http. It is based on documentation at elinux.org: RPi Low-level peripherals
It is tested with Winstone Servlet Container, but any other servlet engine will probably do, too.


  • Every port can be set as input, output or analog input (requires a simple circuit based on raspberrypi-spy.co.uk: Reading Analogue Sensors).
  • Output ports can be set conditionally on values of input ports (i.e. darknessSensor1in==1&lamp1out=1, see cron.conf).
  • You can give each port a custom name to make your client look better.
  • You can define a default state on output ports.
  • You can define a blocking time for an output port (so it is not switched to fast in case the user makes a request twice).
  • You can define a toggle time for an output port (i.e. if you want to turn a port on for a defined period of time, it can be done with a single request).
  • You can set a simulation mode for testing your client.
  • Setting multiple ports in one requests are set one after another, but the code is optimized and nothing unnecessary is done in between (it takes about 2-5ms on an idle Raspberry Pi to set all 17 ports, some artificial load (e.g.’find /’ in the background) will slow it down to 10-15ms).
  • Cronjobs (exact to the second) for output ports are based on quartz-scheduler.org. Output ports can be set conditionally and you have a simple but powerful semaphore mechanism.
  • You may define your own variables with a prefix VIRTUAL which are persisted in memory (unknown virtual variables default to “0”).

Planned Features

  • If GPIO ports are used to represent binary output values, blocking single ports is dangerous: Delayed/Queue requests
  • Automated tests
  • Custom hooks (pre/post), e.g. for notifications
  • More status and configuration information requestable via json (disengageable)

Possible Unplaned Features

  • Bit sequences (especially with AUTO.TOGGLE.TIME) for serial output or to control a servo (probably an SPI interface)
  • Some kind of PLC (Programmable Logic Controller)
  • Suggestions are welcome

Project Status

The project has started and I use it by myself mainly for simple output (manually and with cronjobs). If I had to give it a release number, I would say it is a 0.85 release. Bug reports and feature requests are welcome.

Read more.

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