How to connect a non-buddy Tx'er? - JR Pulse Laser 4 channel Tx

[texy]

Hi to the group!
I have one of the above transmitters and I would like to interface it to my PC. Its about 15 years old apparently, and obviously doesn't have a buddy connection. I see on the fms manual page that people have been able to connect to other non-buddy transmitters and I would like to be able to do the same to mine. I,ve taken a scope to the circuitboard inside and found what I think is the right signal (there is only 1 IC on the board!, but I would like clarification. Can anyone point to a link showing a the signal that I am looking for? The one I think it is has basically 4 positive going pulses that move position when I move the sticks around (which sounds about right?. All that needs to be done is convert the signal to TTL levels for the parallel port to recognise (or in this case, to 'clip' the voltage using the zener diode).
One other question - do you remove the xtal when the Tx is connected to your PC ?
TIA
Texy

[Steve Lewin]

Have a look at

Risto has some good shots of the PPM encoder signal you need (8 channel in his case).

Yes if you take the crystal out there is no RF and the battery lasts a lot longer.

Steve

[texy]

Thanks for the quick reply, Steve.
It looks similar to the pin I,m looking at (but mine is only 4 channels of course), except that the
blanking pulse is low where I look, and high on Risto's pics.
I wonder if that's important?
Texy

[Steve Lewin]

If the synch pulse is low then the others should be too. The high pulses should be fixed length and it is the low level bits that change length as the channels move i.e. the whole signal is inverted. I don't know if it makes a difference, it depends exactly how the port is read.

I've had a few problems with the parallel port interfaces so I always use the serial port version but you should be o.k. If it doesn't work just add a transistor to invert the signal.

Steve

[texy]

Thanks again for your help, Steve.
I have done it!
The correct signal was TTL level anyway and all I needed was
the 680ohm series resistor to the parallel port (plus 0Volts).
It was much simpler than I thought. It did take a bit of butchering to the case for the connector, but it doesn't look too bad.
Actually, flying the planes with the Tx is harder than I thought it would be - and I have yet to fly my trainer for real.
Texy