Added support for FRM303, enhancement 2863

[richardclli]

Fixes #2863

Summary of changes:

[richardclli]

I have successfully added support FRM303, and it works in my EL18. This change will not affect the MPM, the MPM is ok as well.

@raphaelcoeffic There are 2 points may need to check:

1. The current FRM303 uses normal TX/RX while the MPM uses inverted TX, I just put the code in the init and deinit of the ext AFHDS3 module.
2. The ext FRM303 and int IRM301 uses different framing address, not sure if we need to put the selection in the UI as well.

[richardclli]

Besides Flysky radio, I think it may not work on TX16S because of the buggy MB that frozen the Heartbeat pin. However even the heartbeat works, it will forces the TX/RX to be inverted, right?

[richardclli]

Rebased after module-api merged. Need to test again later this week.

[raphaelcoeffic]

@richardclli other than the extra line, I'm good with it, let's have this module supported!

[richardclli]

@raphaelcoeffic However, I discovered something bad when testing it. A crash occurs when using the internal IRM301 alone and did not plug in the FRM303. Not sure why. It works ok without my changes. And the same changes works in 2.8 branch as well.

[richardclli]

The crash is finally fixed. It works now for both int module IRM301 and ext module FRM303.

[richardclli]

@pfeerick This should be ready to merge to main.

[jmxp69]

Just to confirm, when merged, FRM303 works with EL18 only and not TX16s?

[richardclli]

Yes, not worked for now, hardware limitations. Need Flysky to work out another serial connection mode in FRM303, before we can work on the support for other radios. TX16S mk1 has bugged heartbeat line, and besides this bug, softserial required as the signal is non-inverted, while TX16S forced invert the PPM and heartbeat line. Therefore best solutions is to make use the S.Port line for half-duplex communication.

[xiaoyigg]

Is it possible in the future?

[richardclli]

Sure will work in the future.