Receiver Tab

Introduction

You install an RC Receiver (Rx) into your aircraft in order to receive radio control (RC) commands from your RC Transmitter where the Rx then sends them to your flight controller over a wire connection to a Serial UART Port using a particular protocol. This guide assumes you have connected your Rx to a Serial UART Port on your flight controller and have set the correct port on the ports tab.

Binding

Before you can know if you have configured INAV to talk to your Rx, you need to be sure your Rx has a bind to your RC transmitter. There may be a blinking light pattern or some way as outlined by the documentation of your radio to know that the two have a bind and are talking to each other.

Receiver Mode

This is where you tell the FC what type of Rx you have and what protocol it speaks.

Receiver Type
This is the first step get INAV to talk to your receiver.

• Serial Receivers - your Rx is 99% likely to be a serial receiver. These can be TBS Crossfire / Tracer, ExpressLRS, Ghost, FrSky, Spektrum, FlySky, etc.
• MSP RX (very rare)
• SIM SITL (for computer simulator use only)
• PPM Receivers (obsolete INAV 3.x and below)

Warning: Do not connect an Rx to a Soft Serial Ports as these ports often drop data which can cause unintentional failsafes and other unexpected behaviors.

Serial Receiver Provider (Receiver Protocol)
INAV can't talk to your receiver until the serial protocol is set. Select a protocol and press Save and Reboot. Once INAV Configurator reconnects, a working connection will be evidenced by moving color bars in the Channel Map that move with your stick inputs.

• CRSF: TBS Crossfire / Tracer, ExpressLRS (all frequencies) | ?? Channel Limit
• FBUS:
• FPORT2: FrSky | 16 channels | RC Control and Telemetry over one-wire connected to a TX UART
• GHST:
• IBUS: FlySky | 10 channels
• JETIEXBUS:
• MAVLINK:
• SBUS: FrSky, Futaba, ExpressLRS (all frequencies) | 16 channels | See SBUS labeled pad on your FC (an inverted RX UART)
• SBUS_FAST:
• SPEK1024: Spektrum** Spektrum DSM
• SPEK2048: Spektrum** Spektrum DSM2 / DSMX
• SRXL2: Spektrum** Spektrum | newer Spektrum protocol
• SUMD: Graupner | 16 channels

Depending on the receiver specs, protocol used, radio limits, etc. there may be a limited number of channels available for your use.

Some Rx can be configured to export a talk a protocol or use different protocol options. This is not common. The extreme case is where ExpressLRS Rx can talk many protocols with many options such as CRSF, inverted CRSF, SBUS, inverted SBUS, etc. Some old FrSKY receivers can be changed by flashing a different firmware while the ACCESS Rx can be either SBUS and FPort in the transmitter model setup page.

IBUS RX and IBUS telemetry can be configured to both be on the same Serial UART - see Telemetry.md

SRXL2 provides both RC control and telemetry over a two-wire connection to UART but requires special cli settings.

RC Smoothing

This is used to filter out jitters in the RC values coming from the sticks on your transmitter. You should leave this ON in almost all cases and the defaults for the other values in this section should be fine for all most cases. A higher value for Manual LPF Hz or auto smoothing factor will add delay to you controls from the filter calculations. So adjust these values only if you understand what you are doing.

Channel Map

The first four channels of almost all radios are dedicated to the values of the sticks. INAV needs to know which channel is which in order to understand your inputs. So we need to map the channel for each stick from your radio to the matching inputs in INAV using the Channel Map. The four letters TAER represent this mapping. This would be Ailerons (Roll), Elevator (Pitch), Throttle, and Rudder (Yaw). There is a drop down box with two presets, AETR and TAER. 99% one these two will be the correct setting. There is also the option to manually type these four letters into that box to change the channel mapping. After selecting a channel order, press Save and Reboot before you can see the changes take effect. You are looking for the color bar labels Roll [A], Pitch [E], Yaw [R], Throttle [T] to match the stick inputs on your transmitter.

This is a great time to check your radio. INAV has its own settings for trim so make sure the trims on your transmitter are set back to the middle on all four sticks. You can check this by looking at the channel values on the color bars. The should be at 1500 in the middle. This is also a good time to check the stick gimble calibrate in your radio’s settings. Find a video on YouTube specific to your radio model.

RSSI Channel (Received Signal Strength Indicator)
Some older receivers use a radio channel to communicate the health of the radio signal. You can tell what this channel is as it will be jittering up and down especially can you move your transmitter around. Many times its channel 16. But modern receivers with telemetry enabled don't need this set at all and this setting should be Disabled.

Advanced: RxRange

INAV expects your transmitter/receiver to send RC values (called end-points) with a range of 1000-2000. But some transmitters/receivers have a non-standard end-points (i.e. 1070-1930 as some Spektrum receivers) which can be a problem in INAV. To adjust for this, go into your transmitter settings and try to set the output end-points as close as you can to 1000-2000. If you still can't get end-points to 1000-2000 then you can go to the cli and use the command rxrange to map your non-standard range to the standard 1000-2000 in INAV.

1. If you used rxrange in the past, reset it by entering the following command into the CLI:

rxrange reset
save

2. Reconnect INAV Configurator, go to the Receiver tab, move one stick at a time on your transmitter to the min and max values (first 4 channels) and write these values down. Always take care to avoid accidentally arming your craft. Go to CLI and set the min and max values with the following cli command rxrange <channel_number> <min> <max> and note that Channel 1 is 0 in the cli, and 2 is 1, and 3 is 2, and 4 is 3. Here is an example.

rxrange 0 1070 1930
rxrange 1 1070 1930
rxrange 2 1070 1930
rxrange 3 1070 1930
save

You can also use rxrange to reverse the direction of an input channel, e.g. rxrange 0 2000 1000. But be sure to know what you are doing whenever usinf the cli.