Problema PPJOY + Porta parallela risolto

[hdevil]

Salve a tutti,
da poco ho cominciato ad avvicinarmi al modellismo, in particolare all'elimodellismo.
Mi è stato regalato un Eco-Piccolo Versione 2 e ,dopo averlo costruito e aver raccolto
informazioni, ho subito compreso che era necessario allenarsi con un simulatore prima di tentare
di farlo volare!

Questo post è per tutti quelli che hanno problemi con l'interfaccia Zener+Resitore per collegare il RC al PC tramite Porta
parallela e PPJOY, questo post POTREBBE (e sottolineo POTREBBE) essere la soluzione ai vostri problemi.
Scusate, ma il resto del post lo metto direttamente in inglese perchè ho intenzione di postarlo anche su dei FORUM
internazionali

Here the story begins.
I tried to use PPJOY + Zener-resistor on the parallel port to interface my R/C to the PC.
My RC outputs PPM with TTL levels, it's a LEXORS NOVA 4+1.
Like many people, I found out It doesn't work with my hardware.
After several days of issues I found the problem!
At the beginning I thought it was a software problem, something wrong with PPJOY accessing to parallel port,
or stuff like that.
I was wrong, indeed now I want to say a public thank you to Deon van der Westhuysen (author of PPJOY)
for the great job he made.

If you experienced problems connecting your R/C to the Parallel Port, and you are sure every software configuration
and hardware connection is good, maybe (I said MAY be) the following is the solution to your problems.

How I found out the solution:
I measured my R/C output impedance and my Parallel Port pull-up resistor.
My R/C source a signal with a 0.5 kohm output impedance which was read by
parallel port having a 0.7 kohm pull-up resistor!!!Of course, this means the signal is killed by the (strong)
pull-up resistor of the parallel port unless we pull-down the output impedance of the R/C!
( Th resistor is too low, It looks like very strange, do u have any ideas? )
Solution:
I cut out the orignal circuit and I put a Follower between the R/C and the parallel port, this did the trick!
(see schematic)

U can use whatever kind of follower you want, I used a LM358 (single supply op-amp) supplied by a +5V stabilized voltage.
Just remember that the output of the follower should not go beyond +5V, because Parallel Port expect TTL input levels.

If you have critics, appreciations or suggestions,
please reply.

Spero che questo post eviti a qualcuno di perdere tutto il tempo che ho perso io
con quell'interfaccia.
Felici voli simulati a tutti.
Ciao raga


Lilo