So, who's going to be first...

[Pchristy]

... to produce an OpenTx compatible encoder board, then?

https://www.theregister.com/2021/01/21/pi_pico/



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Pete

[Mike_K]

Hi Pete

Only 3x ADC inputs though, that's really disappointing (unless you only want 3 channels)

I suppose you can interface an ADC vis I2C or SPI?

[Martin]

I read elsewhere that there are four analogue input pins. Still not enough for a typical transmitter. Also, it only uses the regulator as a voltage reference for the ADC, and there are notes in the data sheet saying what tricks you should use to help eliminate noise on the analogue conversions.

You can fit an external voltage reference in the 2V to 3V range, if you wish.

There are plenty of existing boards capable of OpenTx (multiprotocol) compatibility. The problem for retro transmitters isn't really the chip - it's the display and navigation buttons required to allow selections to be made and stored. Most retro transmitter builders don't want a big display and loads of buttons added to their transmitters!

Several times I've thought about using a smart phone, connected either by WiFi or Bluetooth to the transmitter, to act as a programming/model selection screen. The easiest way is probably via WiFi - then you don't need to write a special app for iPhone and Android - the user would just open a webpage served out by the transmitter WiFi hot spot using their phone's browser. Once the editing or selection has been done, the connection would not be needed for flying. But lots of people have told me that's not really in the spirit of vintage transmitters - so I've not felt motivated enough to go through with the project.

[WernerL]

Several times I've thought about using a smart phone, connected either by WiFi or Bluetooth to the transmitter, to act as a programming/model selection screen. The easiest way is probably via WiFi - then you don't need to write a special app for iPhone and Android - the user would just open a webpage served out by the transmitter WiFi hot spot using their phone's browser. Once the editing or selection has been done, the connection would not be needed for flying. But lots of people have told me that's not really in the spirit of vintage transmitters - so I've not felt motivated enough to go through with the project.

A few years ago I did just that: https://github.com/laneboysrc/rc-headless-transmitter

I am using it ever since, but I don't recommend it to anyone as the Web-software would need a lot of work (and it took already half a year of nothing-else-hobby-wise to get to that point ). Right now you have just basic mixer elements, no high level functions like V-tail etc.

Instead of Wi-Fi, I am using USB. Chrome based browsers support WebUSB, which means the STM32 USB can directly talk to the web browser on my phone (or PC).
Originally I had a SBC simiar to a Raspberry Pi with an NRF chip to bridge between the phone and the transmitter, but now with USB it is faster, more reliable and easier.

I have several 80ies car radios converted with that system, and a few stick radios including a Heathkit single stick and a World Engines single stick. My "daily flyer" is a modified Graupner E8 (Sanwa design).

cheers, Werner