AVR controlled RF light switches

From Just in Time

Revision as of 23:24, 21 July 2015 by Danny (talk | contribs)

Although the Cheapest ever 433 Mhz transceiver for PCs still functions in all its ugliness, there are some things left to be desired in this solution. Particularly, the system needs a PC or Beaglebone/Raspi running for control of the light switches.

I'd like the simpler devices in my home to communicate with each other with only optionally a more initelligent controller in between. I'm working on a "multi-media" bus protocol for my devices (working title: ThingBus) that would work on TCP/IP, UDP, serial ports and through cheap NRF24L01+ transceivers. As a first use case I'm now trying to control the RF switches from an AVR that will listen to NRF24L01+ messages.

It would be silly to have the AVR store the audio samples that were created in the 433Mhz transceiver solution. We need to somehow describe the protocol in a more compact way. This page describes that way.


The image below shows an Audacity screenshot of an audio card capture of the signal of one RF remote. A few things stand out in this signal:

  • It seems to consist of only two types of pulses: wide and narrow. All wide pulses have the same duration and the same is true for the narrow pulses.
  • The rising edges of the pulses in this signal are evenly spaced in time (measured in Audacity to be approximately 33 samples or 750μs )
  • There are 25 pulses in this signal and (not visible in this image) the same train of pulses repeats after some 6ms.

OnA signal in Audacity.png