How to control the plane with your RC transmitter. You will need a transmitter with a buddy box interface, and you will need to make a cable to connect to the parallel port on the computer. I have a Hitec Focus 4. The socket on it looks like: * S * S - is the pulse coded signal G G - is ground in the center position. * * _ Your plug may be different. You can use the program txtest to view if you have a signal or not. txtest has two commands, 'Esc' exits and 'i' inverts the signal. When things are working correctly you should see a signal that looks like: ------ ------ ------ ------ ---------------------------------- | | | | | | | | | --- --- --- --- --- ( This is for a 4 channel radio, if your radio has more channels you will see more pulses ) If you see a signal, but it looks inverted then try the 'i' command. Debug mode - I added another command to txtest. The 'a' key will put the program in auto trigger mode. Use this to test voltage levels when debugging your circuit. This makes the program somewhat like an o'scope in auto trigger mode. To test your circuit, run txtest, press 'a' key. The signal should start as low. Apply 5 volts between ground and the signal input and the signal should go high. If this doesn't work, there is something wrong with your circuit wiring. When this works, hook up your radio, press the 'a' key to turn off auto trigger and the signal should sync as shown above. The cable needs a few parts that can be purchased at Radio Shack or some similar store. Parts needed are: some cable ( shielded may be better, I am using non-shielded ) a DB25 male connector 2 resistors 10k should work ( my circuit has a 20k and a 5k ) a NPN transistor like a 2N2222 Plastic DB25 hood. You can wire the circuit right on the db25 and enclose it in the hood. Radio Parallel Port NPN 5k to 10k -----+-/\/\/\/\/\-----O pin 16 / C | 10k to 20k B|/ -----------------O pin 10 S--------------\/\/\/--------| |\ _\/ E G-------------------------------+---------------------O pin 18 Ground from the radio is connected to ground on the parallel port. The output bit on pin 16 is used to power the pullup resistor. The signal from the transmitter is isolated with the 10k to 20k resistor and drives the base of the transistor. The emitter is connected to ground. The collector is connected to the pullup resistor and to an input bit on pin 10. Check for shorts with an ohmmeter before you plug the cable into your radio and parallel port. --------------------------------------------------------------------------- Once you get this working, just turn on the radio and start FlyRc. The program will detect the radio only at startup, so it is important to start the radio first. At this time, if the radio is turned off before exiting FlyRc, the program will hang looking for the radio signal. Also, boot to a dos prompt before running FlyRc with a radio transmitter. If you leave Windows running in the background, the radio signal counts will be very unstable and you will think you are flying in a strong gusty wind. If your transmitter has a different channel setup than mine, you can alter the channel assignments using the file radio.cfg ---------------------------------------------------------------------------- There is little chance of hurting your radio or parallel port with this circuit. The base resistor prevents loading the radio and the transistor buffer/switch is a common method used to interface with TTL signals. The important points are: 1) Test that there are no shorts before you plug it in. 2) Double check that the connections to the parallel port are on the correct pins. ( you may need a magnifier to read the numbers on the DB25 ) ---------------------------------------------------------------------------- Notes from users: Another option: One user reports successful operation by using servos to drive potentiometers connected to the joystick port. This may be a good use for an old wide band transmitter and receiver. The JR stereo plug interface needs a 22 k resistor from the signal-in pin to ground in order to enable the signal out on the signal-out pin. THE FUTABA ALSO HAS A 6 PIN DIN SO BY MEANS OF PROCESS OF ELIMINATING THE PINS (I DONT HAVE A SCOPE AND USED YOUR TESTING PROGRAMM) AND FOUND IT AS FOLLOWS. THIS WORKS ON FUTABA 8 CH SERIES. G S * S - is the pulse coded signal * G- is ground in the center position. * * _ ( ron - I have read where this diagram is incorrect and that Futaba radio cables are the same as the Hitec. I suggest try the Hitec setup first ) Another Futaba Skysport 4 has this info..... One modification after tracking down the correct pins on the connector for the Futaba (at least the Skysport 4 version) I ended up with: * S * * P * -G- 'P' - is power from this box to a buddy box 'S' - is the pulse coded signal '-G-' - is ground, which is actually the metal shield (or tab) around the pins (the cylindrical part of the DIN connector, not a pin) A Futaba 8UAPS. Looking at the socket on the Tx. ( ron - again I have no way to verify ) G S J S - is the pulse coded signal * G - is ground. * J j - if jumpered togeather then the Tx _ works with Tx switched off, not powering the RF Module, increasing battery life. ------------------------------------------------------------------------ The file XP652.pdf has a circuit design for a JR XP652 radio.