rfswitch

Utility for controlling RF-based power sockets from the Raspberry Pi.

There are two modes of operation; switch and record. The record mode can be used to record and decode the messages sent via the RF remote. The switch mode can be used to turn a socket on or off using the codes captured from the record mode.

Capturing Control Codes

To capture the codes emitted by the remote control, you can use the record functionality provided by rfswitch. In order to use this function, you must have PortAudio installed and have built rfswitch with PortAudio support.

To run record mode, simply type::

$ ./rfswitch r

You will be prompted to select an input device which is connected to the RF recevier. After you select a device, press repeatedly (or hold down) the same key until the entire code has been recorded. The output will look something like the folowing::

Available input devices
  [1] Built-in Microph, input channels: 2
  [2] Built-in Input, input channels: 2
  [4] Soundflower (2ch), input channels: 2
  [5] Soundflower (16ch), input channels: 16
Select input device: 2
Listening on device 2 (Built-in Input)
.....................
Found code
  code:     0110100010000100
  hi-long:  74
  hi-short: 21
  lo-long:  84
  lo-short: 31
  timings:  476190,1904761,1678004,702947

Done recording samples

The important lines here are code: 0110100010000100 and timings: 476190,1904761,1678004,702947. The code line defines the actual signal that the reciever on the selected socket will respond to and the timings line contains the duration of the pulses that make up the signal.

You will then need to create (or update) a configuration file that holds all the codes. Every code needs an ID and an on and off code. The format of the config file is::

<id 1>
<on code 1>,<short-hi>,<long-lo>,<long-hi>,<short-lo>,<delay>
<off code 1>,<short-hi>,<long-lo>,<long-hi>,<short-lo>,<delay>
<id 2>
<on code 2>,<short-hi>,<long-lo>,<long-hi>,<short-lo>,<delay>
<off code 2>,<short-hi>,<long-lo>,<long-hi>,<short-lo>,<delay>
...

The default config file is located at ~/.rfswitch. If the file doesn't exist, just create it:

touch ~/.rfswitch
nano ~/.rfswitch

Now we need to add the codes that were retreived from the rfswitch r command to the config file. Each set of on and off codes need to have unique IDs, which should be positive integers. Using the above example, we can add the following to ~/.rfswitch::

1
0110100010000100,476190,1904761,1678004,702947,10000000

We then need to capture the off code for the same switch.

Example Signal

Here's an example of a typical (but short) RF signal that might be used to control a switch (e.g. turn switch 1 on)::

       0         1         0       0         (delay)    code-bit
    ├────────┼───────────┼────────┼────────┼─────────┼
 hi ┌──┐     ┌──────┐    ┌──┐     ┌──┐
    │  │     │      │    │  │     │  │
    │  │     │      │    │  │     │  │
    │  │     │      │    │  │     │  │
 0 ─│──│─────│──────│────│──│─────│──│───────────────
    │  │     │      │    │  │     │  │
 lo ┘  └─────┘      └────┘  └─────┘  └───────────────
     2   5      6     3   2    5   2    5      8        length

In this example signal the lengths of the individual signals are:

hi-long   6
hi-short  2
lo-long   5
lo-short  3
delay     8

Credits

The idea for this project and much of the switching code is thanks to Geoff Johnson.