RC Buddy Box

In this project I replaced the transmitter electronics of a salvaged, early 1980's, SANWA STAC-6 transmitter with a circuit that generates a PPM signal as a buddy-box controller. The project is based on AVR ATtiny84 that is connected to the original five potentiometers: four controller 'sticks' plus one 'flap' position. The AVR generates an 8-channel PPM signal from the five control inputs as: five active and three dummy channels. The code makes use of AVR's Timer0 to time the short pulse and Timer1 to time the variable channel pulse duration. Two interrupt routines toggle the output line to composed a signal that is compatible with FlySky FS-i6X RC controller. Other controllers may be tested and listed here.

This is a good reference on how RC PPM works.

AVR ATtiny84 code repository on GitHub.

Board schematics and breadboard layout download.

Features

• Channel reversal DIP switches for Ch.1 Rudder/Ailerons, Ch.2 Elevator, and Ch.4 Ailerons

• Stick range calibration mode

• Preserve stick calibration through power cycle

Stick range calibration

1. Turn system 'OFF'

2. Center all trims and sticks

3. Set calibration DIP switch to 'ON'

4. Turn 'ON' the system

5. Move **all** sticks from minimum to maximum through full motion range (up/down or left/right)

6. When done, move calibration DIP switch to 'OFF'