The Falcon boards use generic +3.3V serial ports. However, to connect to certain radio controlled manufacturers’ devices it is necessary to use external interface boards. On the current Falcon 1, 2 and 3 Rev 1.0 boards, external interfaces may be required for SBUS receievers, FrSky S-PORT telemetry and Minim/Micro Minim OSD.
The interface boards detailed below use easily obtainable electronic parts, to facilitate anyone who is interested in creating and soldering the boards themselves.
SBUS Inverter (Falcon 1 and 2)
The SBUS standard reverses the polarity of a standard serial port signal. The Falcon Rev 1.0 boards therefore require a special, external, +3.3V compatible SBUS inverter circuit shown below:
The flight controller connector is attached to the Falcon’s throttle channel, while the receiver’s goes to the SBUS channel.
FrSky S-PORT Telemetry (Falcon 2 and 3)
Some FrSky receivers use Smart Port (S-Port) telemetry, to allow the flight controller to return flight data back to the transmitter.
Transmitters such as the Taranis X9D allow alarms to be set, for instance for low battery level or maximum altitude.
The flight controller connector is attached to the Falcon 2 or 3’s central Serial2 port, while the single wire connects to the receiver’s S-Port connection. Note that the receiver’s ground is provided by the main (CPPM or SBUS) connector.
Minim/Micro Minim OSD (Falcon 1, 2 and 3)
To interface the Falcon boards to a Minim or Micro Minim OSD requires a simple I2C Level Shifter. The level shifter is required to protect the Falcon 1, 2 or 3’s +3.3V output, from the +5V OSD receiver pin during start-up.