SpeedyBee F405 Wing soft serial fix

The SpeedyBee F405 Wing is an inexpensive but fully featured flight control board for INAV or Ardupilot.

The first release INAV 6 firmware for this board did not have soft serial support enabled, so it was not possible to use Smart Port telemetry from FrSKY receivers.

Smart Port connection from an FrSKY receiver allows all telemetry to be sent back to the radio.

Here are the updated firmware hex files to enable soft serial on the T2  pin of UART2:

SpeedyBee F405 Wing INAV 6.1.0 fix soft serial firmware 

UPDATE JUNE 2023

S8 bug fix - With the factory loaded firmware S8 pins did nothing, S9 acted as S8, S10 acted as S9 etc.

This has been remedied with the release of SB F405 Wing INAV 6.1 firmware. 

INAV UPDATE 

Latest firmware INAV 6.1.1 also fixes the "Dolphining" problem which was introduced by INAV 6.1 to all FCBs

Smart Port Telemetry, INAV and F4

FrSKY receivers with S-Port capability can send telemetry data back to the transmitter. The data can come from FrSKY S-Port telemetry sensors but also from flight control boards (FCBs).

SBUS and Smart Port are inverted signals, compared to normal convention for flight control boards and receivers. Flight control boards need to un-invert these inputs to be usable.

F7 boards have inverters on all UARTs which can be enabled in the configurator, so SBUS and SmartPort inputs can be connected to any UART.

F4 boards only have one UART inverter (for SBUS), usually on the Rx2 pin. But we need an inverted Tx pin for the Smart Port input.

So this is where Soft Serial comes in. Soft Serial creates a software defined UART which can be inverted.

By enabling Soft Serial or "CPU based serial ports" Tx2 becomes available as an inverted pin for Smart Port connection.

The steps below show how:

1. Enable "Enable CPU based serial ports" and "Telemetry output" in the INAV configuration page

2. Choose "SmartPort" in the Telemetry column for SOFTSERIAL1 in the Ports page

3. Choose SBUS, OFF, AUTO or OFF in the Receiver page

4. On the F4 board connect SBUS to the SBUS pin and SmartPort into the TX2 pin

5. "Discover new" sensors on your transmitter, and you should see all the extra FC telemetry appearing.