Trainer level converter idea

[ShowMaster]

The 9x expects to see another 9x as the student Tx along with the 5v ppm data level. Many non 9x brands only output 1.5 to 3 v ppm data. Gruvin has a 1 transistor level changer mod shown on his posted schematics.  I built it and installed it into the 4066s ppm in data line and now I can use many non 9x brand TXs as a student TX.
I'm thinking of putting this circuit in a small external box along with a 9v battery, 5v reg and switch and led. It would have a short output mono plug and a mono input jack and mount with hook and loop (Velcro) to the back of the master tx.
This would make any 9x compatible with many TXs without internal modifications or soldering.
The I transistor circuit does invert the ppm signal so I would use two transistors or an ic to make the output polarity match the input so this could be used for interfacing many brand systems to each other.
The wireless Frsky trainer setup is another option but does limit trainer tx options.
If this is of some interest and has some use to others I'll put it on the top of my to do list to try.
SM

[MikeB]

This sounds like a very good idea. It helps with one of my (many) pending jobs, that of using the PPM-IN pin to drive out a PPM signal for trainee and simulator use. If you do the internal mod, you block this signal route.
The basic transistor mod actually does NOT need any power, so unless you really want a LED, you could get rid of the battery and regulator.
Er9x auto senses the PPM-IN polarity, so it doesn't matter if it gets inverted, so you only need the single transistor if er9x is the master system.

Mike.

[ShowMaster]

Even better news about not needing power Mike.
The led was just because I had a battery designed in the small box already. It can go!
I'll try it today.
The only reason for a non inverting level changer is for use with other brand radios with each other. But this too may not require power.
My club purchased several low end JRs to use with the clubs DX7s and they would not work.
I suspect the ppm level the JR outputs is to low for the DX7?
I own a dx7 and have one of the JRs they can't use to see what's going on. I know the JR does not work with a stock 9x but does with Gruvins mod. This level converter powered or not may be the key to mixing all brand TXs for trainers.
Thanks for the tech notes.
SM

[MikeB]

This may seem surprising, but the 9x has a pullup resistor to 5 volts internal to the processor, so it is just possible a single schottky diode, band away from the 9x, may be sufficient to provide a non-inverting level shifter for the trainer input. You see, I'm not content with slimming down the firmware, I try it with the hardware as well

Mike.

[ShowMaster]

Wow just a Schotty Diode! It's worth a try.
Making room on the bench for this and some other projects. Where does all the clutter come from, I know, you have to throw something away!
I believe I read where many brand TXs are open collector so this may work.
SM

[Crucial]

Did you ever complete the testing on this?

[ShowMaster]

I spent some time on it and never got it working well enough and then got my ersky9x board. I never got back to it. I still think it's worthwhile so maybe others will help get it going again.
SM