Support AUX2 Jumper T15

[r1000ru]

Is there an existing issue for this feature request?

• I have searched the existing issues

Is your feature request related to a problem?

For connecting BLE Telemetry DIY and GPS, as variant

Describe the solution you'd like

Add AUX2 in build action (Serial3 on PB10, PB11 and Serial6 on PG14, PG9), if there are no terrible obstacles.

Describe alternatives you've considered

No alternatives

Additional context

No response

[3djc]

Jumper have asked that this connector stay dedicated to something else.

[mha1]

UART3 (the one close to the STM32) is already AUX1 and working. 3.3V on VCC though.

[r1000ru]

Jumper have asked that this connector stay dedicated to something else.

Maybe it's worth doing something else as one of the Serial AUX connection types (Telemetry Mirror/SBusIN/Jumper something else)?

[r1000ru]

UART3 (the one close to the STM32) is already AUX1 and working. 3.3V on VCC though.

Disgusting. Low-current LDO won't be able to power the Bluetooth module. However, 5 volts from BEC can probably be found.