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Receiver

The Receiver tab configures how the flight controller talks to your RC receiver: protocol selection (serial RX protocols, PWM/PPM, RX-SPI, etc.), channel mapping, and live channel monitoring.

Protocol and signal options

Once a serial RX protocol is selected, three signal-level switches appear that matter more than they look like they should -- get the wrong one and you'll see no signal at all rather than a subtle problem:

  • Serial Inverted un-inverts an inverted signal -- required for S.BUS and F.Port, among others. Not supported on F4-based boards.
  • Half Duplex uses the Tx pin for both sending and receiving -- required for SBUS2, F.Port, SRXL, and SRXL2.
  • Pin Swap swaps the Rx/Tx pins, for wiring that comes in reversed.

SRXL2 full-size receivers

Some Spektrum full-size receivers (e.g. the AR6610T) need to see a valid SRXL2 handshake within about 200ms of power-on, or they revert their receiver port to plain PWM instead of SRXL2 -- which can be too fast for the normal handshake to win the race during boot. When the FC's own SRXL2 unit ID is set to 0 (bus master), it now sends the first handshake packets very early during boot, before this can happen, then continues the normal handshake process as usual.

This is CLI-only -- set it with set srxl2_unit_id = 0. Note the default is 1, not 0, so this needs setting explicitly for a receiver that requires it.

Channel Assignment

Different transmitter brands don't agree on which physical channel carries which stick -- FrSky/ELRS/Futaba send AETR (Aileron, Elevator, Throttle, Rudder) while Spektrum/JR/Graupner send TAER (Throttle first). The channel order preset dropdown remaps for your brand in one click, instead of manually reassigning each channel; the live bars next to each channel let you confirm the remap actually matches real stick movement before wiring up the Mixer.

RSSI can be read from Auto (protocol-reported, if the link supports it), the board's analog RSSI ADC input, or repurposed from any AUX channel your receiver outputs an analog-ish RSSI value on.

Telemetry Sensors

Selects which telemetry values are sent back to your transmitter/OSD, and for protocols with a fixed transmission sequence (e.g. Smart Port), what order they go out in -- data earlier in the list updates more often. Available sensors depend on what the connected protocol and firmware build actually support (e.g. RPM only appears with a configured RPM source).

Virtual TX

For bench-testing without a real transmitter bound, a virtual RX input tool is available (desktop app only) to simulate channel input.

Serial RX #1 / Serial RX #2 (Backup RX Input)

The main receiver's own protocol box is labeled Serial RX #1. Its title bar always shows a Link badge for the main receiver's own live signal state, whether or not a backup port is configured.

If a serial port is assigned the Serial Rx (Backup) function on the Configuration tab, a second box, Serial RX #2, appears below it with:

  • A Protocol dropdown (None, Futaba S.BUS, FrSky FBUS, FrSky F.PORT, FrSky F.PORT2, Jeti EXBUS, or TBS CRSF) -- None is the default, meaning the port is assigned but not yet decoding anything.
  • Inverted, Half-Duplex, and Pin Swap switches, same meaning as the equivalent settings for the main receiver but independent of them -- this is a different physical UART, and each protocol has its own natural wiring convention (SBUS is inverted by default; every other supported protocol isn't), so OFF always means "this protocol's normal wiring."
  • Link and Active Source badges in its own title bar, live-updated, so both boxes show their status right where you'd configure them.

Changes to any of these fields need Save & Reboot to take effect, same as any other serial-port setting.

Once a backup protocol is selected and reporting data, every entry in Channel Assignment grows a second, smaller meter underneath the main one showing the backup receiver's own live value for that channel -- useful for confirming a bound backup satellite is producing sane values before ever relying on it in the air. See Backup RX Input for what the feature actually does.