An Arduino Sketch able to emulate a Somfy remote control.
If you want to learn more about the Somfy RTS protocol, check out Pushtack.
How the hardware works: Connect a 433.42 Mhz RF transmitter to Arduino Pin 5 (or change the pin in the sketch). I couldn't find a 433.42 MHz transmitter so I hacked a remote to send my signals. I then ordered 433.42 MHz crystals to change the regular 433.92 MHz ones I have on my transmitters: that's the cheapest way to do it. Other option would be to use a tunable transmitter (but that hardly looks like the easy way and I'm not a ham radio, so...).
How the software works: What you really want to keep here are the BuildFrame() and SendCommand() procedures. Input the remote address and the rolling code value and you have a remote. With the sketch, you can send the command through serial line but that would be easily modified to button press or whatever (I plan on running it on an internet-connected ESP8266 to shut the blinds at sunset every day).
The rolling code value is stored in the EEPROM, so that you don't loose count of your rolling code after a reset.