Retro Transmitter Retrofit Part 2: Done (with issues)

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:

Throttle and elevator pots are reversed.
Left right menu buttons are swapped (oops!).
Can’t easily access the uSD card
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.