feat: Flysky PL18 Support

[richardclli]

Based on this PR:
#4012

Support of Flysky PL18 with the hardware mod described in here:
https://github.com/EdgeTX/edgetx/wiki/PL18-Hardware-Mod-for-Complete-EdgeTX-Support

Fixes #4380

[richardclli]

@raphaelcoeffic I have made an internal MPM for PL18 using the internal spare UART7 connector, don't breaks it.

[raphaelcoeffic]

@raphaelcoeffic I have made an internal MPM for PL18 using the internal spare UART7 connector, don't breaks it.

Ah ok! Maybe we should have some compilation parameter for that. Currently it's not really easy to understand how that works.

[richardclli]

I will add the information in the mod page this weekend. And opensource the internal MPM design. The current build will only breaks Risto's PL18EV mod. He used the UART7's pin and DAC pin for the gimbals.

@rotorman Can you see if you can figure out a way to support the EV as well based on this working mod?

[rotorman]

Not as DAC, but ADC. I used DAC pin for audio. I cannot find any further analog pin of STM32F429BIT6 that I could use for Paladin EV stick ends (need 4 additional channels, 2 for each stick - one for the stick end pot, one for the stick end both switches that output a combined signal on an analog pin).

[richardclli]

Not as DAC, but ADC. I used DAC pin for audio. I cannot find any further analog pin of STM32F429BIT6 that I could use for Paladin EV stick ends (need 4 additional channels, 2 for each stick - one for the stick end pot, one for the stick end both switches that output a combined signal on an analog pin).

So the UART7 is the only option for you then. So only need to support 2 config: 1. PL18 with optional INT module, or 2 PL18EV with no INT module.

[richardclli]

This PL18 branch is quite stable, I used for flying for some time already.
@rotorman see if you can utilize this branch to make your PL18EV works as well with some options and we can finalize it for merging.

[rotorman]

IMO the decision depends on the amount of users using or to be using in the future of one or the other option and that can give clues in order to decide if the main line of branch should either support optional custom internal MPM or support PL18EV stick end controls.

[richardclli]

I know a few users in China managed to made the internal MPM PL18 mod from my design files. It seems fun to them anyway. @rotorman Could you please add PL18EV part to the mod page for some others who are interested to work it out to give it a try? For myself, I may mod my PL18EV according to your information as well.

[pfeerick]

On finally reviewing all the code for this there are some changes I'm not so happy with... i.e. use of PCB defines when a feature flag could have done. But since it was mostly the NV14 that was guilty of that and you've just added the PL18 to the mix, I will do a followup PR to try and clean most of that up instead of hold this up.

[richardclli]

Yes, indeed. Let me know if you need any help.

On finally reviewing all the code for this there are some changes I'm not so happy with... i.e. use of PCB defines when a feature flag could have done. But since it was mostly the NV14 that was guilty of that and you've just added the PL18 to the mix, I will do a followup PR to try and clean most of that up instead of hold this up.

[rotorman]

PL18 and PL18EV could be added also to https://github.com/EdgeTX/edgetx/blob/main/tools/boards.py

[pfeerick]

Do we even know what that file is used for, or is it a legacy file that should be bumped off? If not, it's missing more than a few boards, not just the PL18 🤭