Sunday 25 June 2023

INAV trouble-shooting checklist

What to check if your INAV setup is misbehaving

1. Radio setup

The model setup must have no mixing, no rates, no expo, no flight modes and no trims. Just 100% inputs for the first 4 channels. 

The plane-type selection, mixing, rates and expo are set up in INAV, not the radio.

GOLDEN RULE - Don't use an existing model setup and edit it for INAV. Make a fresh blank model in your radio to ensure there are no leftover mixes, trims, logical switches or overrides.

Configure your model like this -

Ch1 - 100% Aileron 

Ch2  - 100% Elevator 

Ch3 - 100% Throttle

Ch4 - 100% Rudder

Ch5 - usually Arming switch (specially for ELRS)

Ch6 Ch7 Ch8 Ch9 etc - Mode switches

The same model works for flying wings, conventional planes, twins, V-Tails and even quads

Connect your receiver to the designated Serial RX UART on the FC and connect the FC to your computer. 

Check that the channel bars in the receiver page move to the right when the 4 sticks are moved up and right.

If a channel bar moves the wrong way, invert the channel in your radio. This makes sure the stabilisation will work in the correct direction.

Note that the Roll Pitch Yaw Throttle bars do not match the channel order of Ch1 Ch2 Ch3 Ch4. As long as the stick inputs give the correct response all is good.

2. Receiver connection

If the channel bars don't move at all when you move the sticks - 

Check receiver is actually bound correctly to the INAV model in your transmitter. Use a servo/signal checker if in doubt. 

Check the receiver is powered on. Not all boards provide power to the receiver via the USB plug. Some need a battery connected to the FC.

Check your receiver is actually producing a serial signal like SBUS, iBUS or CRSF. Some receivers need to be switched from PWM to Serial output. 

Check the receiver is plugged in to the correct UART on the board and this UART is set to Serial RX in the Ports page. 

SBUS receivers often connect to UART2, with SBUS signal on the RX2 pin or the designated SBUS pin.

For ELRS receivers check Receiver RX is connected to UART TX and Receiver TX is connected to UART RX

Check the correct Serial Receiver Provider is selected in the Receiver page - CRSF for ELRS and TBS, or SBUS for FrSKY

3. Control surface movement

If a control surface moves in the wrong direction when you move the sticks - 

For control surfaces on a normal plane you can invert the channel in the Outputs page 

For control surfaces with mixed inputs, like Elevons or V-Tails, reverse the Weight in the INAV Mixer page for the offending control surface mixer line. For example - If the left elevator on this V-Tail is going down instead of up, change the Stabilised Pitch weight from 50 to -50 for S3

If you need to reduce the throws, enter a lower number for the weight in the INAV mixer or Outputs page

4. GPS

If the GPS icon is greyed out or red -

Check the GPS is connected to the correct UART.

Look in the Ports page for the UART with GPS selected.

Check "GPS for telemetry and navigation" is turned on in the Configurations page

Connect the GPS to the recommended GPS UART (or any spare UART) and select GPS as the sensor on that UART in the PORTS page

Normal UART connection - G to G, V to 5V, RX to TX, TX to RX

Compass connection is not required for fixed wing INAV.  GPS can provide all the required heading data. A poorly calibrated compass will cause problems.

Check the GPS has power. Some boards can power the GPS through the USB, others may require the battery to be connected

Once it is connected correctly and powered up the GPS icon (top of configurator window) should turn blue and the Total Messages number (GPS page) should start counting up.

Now it's just a matter of placing the GPS with a clear view of the sky and antenna facing up, and waiting for satellites to be acquired. This can take from a few minutes to over 10 minutes if this is the first connection.

5. Connections

If you are still having problems it's time to go over your connection again.

Check your receiver, ESC, GPS and servos are plugged in where they are meant to be and the right way around. Look at the wiring diagrams on the product page.

Things that often catch me out are -

SBUS-Out from the FrSKY X8R and X6R receivers are in different places.

Changing from SBUS to ELRS on the SpeedyBee F405 Wing, also have to change from UART2 to UART1. 

Layout of the pins on the Matek F405 Wing is quite different to many other Matek boards.

Also check for bent pins and solder bridges.

6. Correct firmware target

Check on the product page for the correct firmware target for your board. 

The target name is sometimes not obvious. For example for the Matek F405 Wing firmware target is MatekF405SE. 

With incorrect firmware, some functions may work OK but no all.

7. ESC constantly beeping

If your ESC beeps continuously it either means your receiver is not connected or the ESC needs calibration.

Make sure you have the correct protocol selected for your ESC in the Outputs page. If in doubt leave it at Standard.

ESC calibration in INAV

Connect the ESC and motor to the board

Remove the prop! Disconnect the flight battery

Go to the Outputs page

1. Slide the "I understand the risks..." button to the right

2. Move the Master slider to the maximum 

3. Connect the flight battery and wait for the ESC calibration beep

4. Slide the slider to the minimum and listen for the ESC calibration done beeps.

Test the motor spin up by carefully raising the Master slider just a tiny amount

8. Motor will not arm

If a GPS is connected then at least 6 satellites and 3D position lock are required for arming.

If you are not using GPS then the Failsafe setting must be Land or Do Nothing, because RTH will prevent arming.

If all the control surfaces are working but the motor won't arm, look along the bottom of the INAV window for Arming flags or error messages. 
9. Servo voltage

It is safest to leave the servo BEC voltage at 5V for widest compatibility. If you have changed to 6V or 8V on the servo BEC make sure your servos can handle it.

Check that all your servos are functional. One burned out servo will stop all of them working.

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