Tools

Logic Analyzer

Helpful to analyze/debug data streams or measure ppm signal length.

saleae (works with linux)

The original costs about 120€, china clones begin at 10€.

There is also an open source support for a lot of different logic analyzers (china clones) sigrok

V-Cable

If you lack servo outputs on paparazzi this V-cable can be useful. Using it you can control two aileron servos on one servo output. Or two or even four flaps on one output. All servos can be configured separately (reverse, neutral, turn angle, etc.).