Retro Transmitter Retrofit Part 2: Done (with issues)

Click here for Part 1

The Retro Transmitter Retrofit!

The transmitter is complete and working!  Feels good and getting used to flying with it.  No issues with using it all yet.  Just a few issues in configuration outlined below.

The original antenna is there and will fully extend! But I don’t want to tempt fate and the internal wiring by sticking in all the way. I put the actual antenna in a switch hole.

From the original concept here’s a few of the changes, challenges and issues.

First, the issues:

  1. Throttle and elevator pots are reversed.
  2. Left right menu buttons are swapped (oops!).
  3. Can’t easily access the uSD card
  4. The whole thing is a “rat king” of wiring and I am not brave enough to open it up again.


Under the cover for the original frequency switches.

I did end up using a LCD and buttons.  The original idea of not using the LCD and buttons was that I could use the PC over USB to configure it and didn’t really need it for flying.  Also the LCD was too big to fit.   But I needed to calibrate the pots which you can’t do with the PC software.  Oops.

I was able to source a compatible smaller “1.8” 128×64,GLCD,Graphic LCD Module Display SPI Serial,ST7565P white Backlight” on eBay for only $6 and like 6 weeks from China but it works great.  This allowed me to make a button-display board that will fit under the flip cover where the channel switches were originally.

Another decision that bit me was the trims.  Decided for quads I never used trims  and I didn’t have an easy way to swap the analog trim pots with switches.    But… apparently the trim switches can be used for different USB boot modes.  I looked into either adding internal switches somehow.  I even made an Arduino lilypad circuit to read the A2D and output the trim button signals but never installed it.

I originally loaded OpenTX as I run that on my Smartyparts upgraded Th-9x and was hoping to get more USB options.  Without the trims for the USB boot options and easy access to the uSD card that wouldn’t work so I went back to ERSky 9X where the voice files were already on the chip and was the default for ArUNI.  I then had to really learn the menus to get things configured right.

Not sure I will use it, it is wired up though.

Battery meter, mostly calibrated and accurate

uUSB is easily accessible. The uSD card is on the same board but not accessible.

The TX status LED and binding button


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