The link between R/C receiver and your PC

Last Updated: Sep 19th 1996

By Cord Johannmeyer, Modellsportclub Achim MSCA, Germany.

This is a small device for all the people that use a R/C Model Airplane simulator with joystick port interface.
It's more fun to control the simulator with the original R/C transmitter!
The file RCFSPIC.ZIP contains all necessary files for construction of a link between R/C receiver and the joystick port.
Recently I've added support for the Graupner/JR trainer cord(see RCFSPIC.ASM).
The device was developed for operation with the RCFS R/C flight simulator by Dave Brown, but it runs as well with all other programs using the joystick port.


The interface actually came into being as a by product, because during training in PIC-programming I was looking for a suitable exercise. The cost was not a big consideration, so as substitute for the joysticks I've used the somewhat expensive digital adjustable resistor X9C104 from Xicor. The essentials of the device are the PIC16C84, 4 x 9XC104, some switches and connectors.


Four servo outputs of the receiver must be connected, typically

or the corresponding channels for a helicopter. The 4 pulsewidth modulated signals or the trainer cord signal are sampled by the PIC, adjusted and converted to the corresponding sliding contact position of the digital potentiometers.
To operate the interface with the Graupner/JR trainer cord signal the "#define SERIAL" switch in RCFSPIC.ASM must be enabled, otherwise comment out this line.
There are 2 modes of operation, the programming mode and normal operation. After toggle of the switch into the programming mode the control sticks must be moved into all end positions. Returning into normal operation mode the end positions will be stored in the EEPROM. This procedure has to be done only once.
The component costs are approximately 65 German mark (Conrad-prices), for the PCB plus a matching box approximately 15 German mark have to be added. The device has been working trouble-free for more than one year with the Dave Brown RCFS R/C flight simulator.


Most of the joystick ports at multi-I/O cards have only 2 analog inputs, contrary to the original IBM-specification. For operation a port with 4 inputs is required, as provided by a lot of sound cards.
Be careful if you connect the Graupner/JR transmitter via trainer cord! The signal level has to be limited to 5 Volts. This can be done by a resistor and a zener diode.

Please let me know about your experience with the RCFSpic.
And keep in mind this is for non commercial use only.

Have fun!

Questions, suggestions etc. please send via email to C_Jhm@t-online.de