RC Groups OpenTX 2.0+ User manual

OpenTX 2.0+ User Guide
User Guide by Authors, for OpenTX 2.0+ last updated 2014.09.10..
Commercial use forbidden without explicit authorization by the Authors and translators. We don't bite, but like to
know what's going on, so just ask :)
This page is intended to describe the OpenTX 2.0+ firmware that can be installed on a number of radio
transmitters, including the Taranis, and offer some explanations about the philosophy of the firmware and how to
set up models. OpenTX 2.0+ is open sourced and one can check the release history of OpenTX firmware on this
page.
We'll start with an overview of menu contents, and then go into more details about how to set up models. The
Taranis version of OpenTX has all of the features from the 9x version, includes the additions of the sky9x version
(splash screen, audio/speech, SD card for model/audio files/logs storage, USB access to card and settings/model
memory), sees the UI adapted to the larger screen and different button layout, and finally adds support for the
Taranis' extra hardware capabilities.
OpenTX 2.0+ User Guide
The FrSky Taranis radio
What you'll find in your package
An overview of FrSky Taranis features
The Taranis hardware
The Turnigy 9XR Pro Radio
What you'll find in your package
An overview of Turnigy 9XR Pro features
The Turnigy 9XR Pro hardware
OpenTX 2.0+ Software overview
Button navigation
FrSky Taranis
Turnigy 9XR Pro
Main views
Telemetry view
Radio general settings
SD browser
Trainer
Version
Diagnostics
Calibration
Model menus
Model setup
Helicopter setup
Flight modes
Inputs
Mixer
Mixer Functions
Servos
Curves
Global variables
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Logical switches
Special Functions
Telemetry
LUA Scripts
Templates (remove or reference companion wizzard /lua wizzard)
First steps
Setting up a model
OpenTX basics
Everything about the mixer screen
Servos screen
Inputs screen
Model setup guidelines
Advanced features
Flight modes
Telemetry values
Audio
Global variables
A few interaction examples
Introduction to OpenTX companion
Basic concepts
Setting up OpenTX companion for the Taranis
Simulating the radio
Update Firmware and Bootloader via SD Card
Updating the firmware of your Transmitter
TX Off method
Installing the driver (for Windows only)
Installing the flashing utility (for Mac OS and Linux)
Downloading and flashing the firmware
Bootloader Method
Tips using OpenTX
User can't connect to the Transmitter via USB using OpenTX Companion
Differences if updating with the Bootloader or using dfu-uti
Use of the EDGE command which replaces Hshort and Hlong
What is Inputs and the difference between "[I]Source" and “Source" in mixes
How to change the splash screen
Use Subtrims to fix mechanical linkage issues
Trims->Subtrims
Instant Trim
The Mix lines is essentially a math pad
OpenTX Sound
Setting up
Rates and Exponential
4 channel fixed wing aircraft
Flaperons
Knife Edge (Aileron/Elevator) Mix
Sequence for Retraction/Extension
Multi Engines
Throttle cut for Electric Powered Aircraft
Throttle cut for Internal Combustion engines
Buddy Box/trainer
Hardware Modifications
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Taranis - Change from Mode1 to Mode2 (and vice versa)
Taranis - SH SF switch swap - Pats solderless method (good for RevA and RevB)
Taranis - Updating internal XJT module firmware
Taranis - Remove clicks on volume changes
Taranis - Updating Speaker & Enhance Sound performance
Taranis - Add Haptic Motor
Resources
Authors
Translators
References
The FrSky Taranis radio
The FrSky Taranis is a ground-breaking radio because it's the first time a renowned player in the R/C industry and
the creators of an open-source radio control firmware collaborate closely to improve both the hardware and
software sides of a product, and come up with an open-source radio targeting the mainstream market. This means
that while the Taranis is a low cost radio, it is free of the usual "marketing-driven" limitations that most
manufacturers place on their offerings, and as such offers features that match and even exceed those of the
highest end radios in the industry.
It is also future-proof, as both teams are always there to respond to questions and suggestions. Things can evolve
quickly to follow the needs of the various users! And should you have some programming experience - the entire
source code of the firmware is available for you to play with and change to your liking.
What you'll find in your package
● An aluminium case (optional on newer sets)
● A radio!
● A 6-cell NiMH battery pack
● A charger that connects to the radio's charge port
● A nice neck strap
● Depending on the chosen combo, an X8R receiver
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An overview of FrSky Taranis features
● Large 212*64 backlit LCD screen
● Quad ball-bearing gimbals with high quality potentiometers
● Numerous input controls (4 sticks, 4 trims, 2 sliders, 2 pots, 8 switches), all freely assignable
● 60 model memories
● 32 logical channels
● Internal telemetry-enabled RF module capable of transmitting up to 16 channels, with a refresh rate of
9ms. Supports the existing D8 protocol (useable with all D-type and VxR-II receivers) as well as the new
D16 and LR12 modes.
● JR-compatible external RF module slot (no 6V supply) supporting transmission of up to 16 channels
(depending on module) in various common protocols (PXX for FrSky modules and PPM for 3rd-party
modules). Support for serial DSM2 for DIY Spektrum modules is also present (see the 9x mod guide for
details).
● Mapping of the transmitted channels is free, so once an external module is added you have the choice of
either creating a redundant system where the same channels are transmitted via both internal and external
RF, transmitting up to 32 independent channels simultaneously, or anything in between.
● Internal RF (and external RF when an FrSky XJT module is fitted) supports receiver lock (X receivers only)
and allows configuring failsafe conveniently from the radio with 3 modes: Hold, Stop pulses, Custom
positions (only available with X-series receivers, D and V-II series use the usual receiver button press).
● Telemetry with 3 customisable screens and fully configurable speech announcements, supports existing
receivers and sensors as well as new Smart Port sensors. Configurable metric or imperial units. Integrated
audio variometer (sensor required on the model). Data logging can be enabled on the supplied microSD
card.
● Selectable stick mode (1-4), totally free output channel assignment.
● 2 timers, values can be stored when the radio is powered off
● 64 mixers
● 9 flight modes
● 16 custom curves with 3-17 points each, freely definable x coordinates
● 32 logic switches
● Standard JR-type 3.5mm trainer jack (PPM signal on tip, ground on sleeve, compatible with both mono
and stereo plugs, ring unused if present), capable of receiving up to 8 channels as input, and sending up
to 16 channels when configured as output. Master/slave mode and signal parameters are conveniently
stored separately for each model.
●OpenTX companion Windows/Mac/Linux software to save, edit and share your models and settings as
well as simulate your model setup
● USB connection for firmware upgrades, microSD card and OpenTX companion access
● Sticks can be calibrated by the end user
● Multiple language support: English, French, Italian, German, Swedish, Spanish, Portuguese, Czech, and
maybe yours if you contribute with your own translation file! (Radio comes in English language, reflashing
is needed to change language)
● Open source community-driven firmware, so unlike with major manufacturers if you need a special function
or have good improvement suggestions just raise your voice, and don't be surprised if it's implemented a
couple of days later! Visit http://www.openrcforums.com to meet the developers!
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The Taranis hardware
The radio has a relatively standard design and control layout, namely:
● 2 sticks and their associated trims, labelled in the software as Thr, Rud, Ele, Ail and TrmT, TrmR, TrmE,
TrmA respectively. The stick to name mapping matches the selected stick mode. Trims are freely
assignable (e.g. for cross-trimming), and can also be used as independent controls.
● 2 adjustment pots, S1 and S2
● 2 lateral sliders, LS and RS
● 6 3-position switches (SA-SE, SG)
● 1 2-position switch (SF)
● 1 momentary switch (SH)
When selecting a switch position to activate functions, it is referred to as the switch name followed by the physical
position (SAup, SC-, SFdown). A ! before the name means NOT, so !SBdown would mean that the function is
active when SB is NOT down, i.e. when SB is either up or in the middle.
A swiveling antenna is installed for the internal RF module, and a speech-capable speaker is located under the
round grill. The large backlit, grayscale LCD and 6 edit keys take most of the lower part.
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The back of the radio shows the JR-compatible module slot, along with a JR-style jack trainer port, USB connector
and earphone jack. The battery bay houses a microSD card slot, a serial port and of course the battery connection.
The supplied battery is a 6-cell NiMH, but the plug will also accept a JST-style balance plug for a 2s Li-Po battery.
Battery compartment dimensions are 108x31x28mm. Voltage range is 5.5-13V for the internal components, but be
aware that external modules might require up to 12V, so observe your module's requirements when using one and
choose the appropriate battery.
The right side of the radio sports the charger input plug, with the charging LED next to it on the back of the radio.
When you connect the supplied power supply the LED will turn on, and shut off when the battery is charged (2-3
hours charge time for an empty battery).
PLEASE NOTE: The radio has an integrated Ni-MH charge circuitry designed to charge the supplied 6-cell
battery.
●Do not connect a smart charger to the charge plug. It should only be supplied with 12V DC, polarity
however doesn't matter.
●Do not use the charge plug if you have replaced the battery with a different type (chemistry or cell
count).
The gimbals have adjustable length and tension, and each of the vertical axes is fitted with a spring disable feature
as well as a ratchet and brake. This means that there is no need to swap parts to change modes, and that if you
want to you can have either both or none of the vertical axes spring-loaded.
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On the inside, the gimbals have 3 different types of screws:
● Y axis ratchet and/or "smooth braking" action strengths (blue)
● Y axis spring disable, screw it in to disable spring (green)
● X and Y spring tension (red), screw in for more tension, outer is Y of course.
It is good to note that if you like having weak stick tension, it is easy to get inconsistent centering when the spring
tension screws are too loose. Just tighten them enough for centering to be good enough, and recalibrate.
Also, if you encounter a situation where your throttle stick does not “stay” at the ends when you release it, it is likely
that that the spring disable screw (green) is simply not tightened all the way. Tightening it completely should solve
your problem.
The Turnigy 9XR Pro Radio
What you'll find in your package
TODO
An overview of Turnigy 9XR Pro features
TODO
7

The Turnigy 9XR Pro hardware
TODO
OpenTX 2.0+ Software overview
Now might be the time to put the battery on charge, so that after reading this section you can directly have a go at
putting what you learned in practice!
Button navigation
FrSky Taranis
The Taranis has 6 input keys: a standard set of +/-/ENTER/EXIT, plus 2 contextual MENU and PAGE keys.
On the main views, the PAGE key will switch between the different views described in the next section. A LONG
press of the PAGE key will bring up the telemetry display. A SHORT press of the MENU key will call the model
menu, while a LONG press will call the radio settings menu. In those 2 menus, a SHORT press of the PAGE key
goes to the next page, while a LONG press goes back to the previous one. EXIT goes back to the main views. In
all model menu pages a long press of the MENU key will bring up a channel monitor to allow quickly checking the
influence of a change in settings on the outputs.
The navigation in a menu is simple: The +/- keys will navigate up/down between editable fields, or lines of fields
depending on the screen.
ENTER will enter the line of fields when applicable, then edit mode. In edit mode, +/- will change the value, ENTER
or EXIT will validate the input and return to navigation. EXIT always goes back to the previous navigation level.
In edit mode, we have four 2-key shortcuts available:
● +/- together: Invert value
● -/ENTER: Set value to 100
● EXIT/PAGE: Set value to -100
● MENU/PAGE: Set value to 0
Another handy feature is the auto selection of physical inputs in the relevant fields. Instead of choosing a source or
switch with the + and - keys, just move the pot or flick the switch you want, and it will be recognised. For switches
the position is also auto-selected, and the +/- double key combination will allow selecting the opposite position
(!Sxy) in a pinch.
Turnigy 9XR Pro
TODO
Main views
We have 3 main views showing the same basic information in the top part and different inputs/outputs on the lower
part. On the main views a long press of the ENTER key brings up a menu where you can reset the timers,
telemetry data (min/max values, altitude, GPS home...), all of those, bring up a statistics view (throttle graph,
timers), or show the developer credits. As mentioned above, a short press of the PAGE key switches views.
The new title bar includes radio battery voltage, receiver signal strength (for FrSky telemetry-capable receivers),
main onboard voltage (can be receiver battery, flight battery, or anything else depending on sensors the "Voltage"
parameter in the telemetry settings), status icons (SD present, USB connected, trainer port mode, logging in
progress), audio volume and time.
The other "always present" items are model name, flight mode, and trim/pot positions. The logo is of course
customisable, you'll be able to load your model's photo there! See this thread for a great collection of models made
by the community.
The first view lists the physical switch states in the bottom left zone, and the 2 timers (when enabled) on the right.
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The second shows the gimbal and switches positions, and is handy to check that all the physical controls respond
as intended.
The third shows again the physical switches on the left, and the states of the 32 logical switches on the right.
The last view is a channel monitor showing the servo outputs for all 32 channels (+/- change page). If channel
names are defined on the SERVOS page, they will show up here instead of the numbers for convenience.
Telemetry view
A LONG press of the PAGE key from any of the main views brings up the telemetry views. The PAGE and +/- keys
will then cycle between the power status screen (voltage, current, power or A1/A2 if not set, cell voltages from an
FLVS-01 sensor if connected), the min/max and GPS coordinates screen, and if defined from one to three customs
screens that can hold up to 12 items each, configured in the telemetry setup menu.
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Radio general settings
A LONG press of the MENU key brings up the mostly self-explanatory radio setup menu:
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● Date/Time: To be set, they serve as info but also to give a correct timestamp to files and logs saved by the
radio.
● Battery range: range of the graphical radio battery meter on the main views. To be set accordingly with the
battery type you use (2s lipo here).
● Sound settings: Mode, Master volume, individual volumes of all mixed sources (Beeps, sound files,
variometer, background music), beep duration and pitch.
● Contrast: Screen contrast setting.
● Alarms -> Sound off: if "Sound Mode" is "Quiet", the radio will not even sound warnings like a low battery.
This alarm will remind you of that when turning the radio on.
● Inactivity alarm will remind you if you have forgotten to turn the radio off.
● Backlight -> Mode: If set to Keys, Controls or Both, the backlight will turn on when a stick/switch is moved
and/or a key is pressed, for the duration set below.
● Backlight -> Alarm: Backlight will flash when an alarm sounds.
● Splash screen: On Taranis the splash will always be shown as the memory takes some time to load.
Setting this on will just show it for longer.
● GPS time zone is there to show you the correct time when a GPS is present, and coordinate format lets
you adjust display format to your liking.
● Country code: Must match your geographical location to keep RF transmission parameters within
regulatory requirements.
● Voice language: Allows you to choose the language of the voice announcements. Note that the list
contains all supported languages, but you also need to ensure a voice pack for that language has been
loaded onto the SD card (in a subfolder of the SOUNDS directory).
● Units: Allows choosing between metric and imperial units for telemetry values.
● FAI mode (if the "FAI choice" option is selected in OpenTX companion): Disables all telemetry displays
other than RSSI and voltage to comply with contest regulations. This is one-way, i.e. when you turn it on
with this menu option it can't be disabled anymore, you need to connect the radio to the PC and use
OpenTX companion to turn it off again (to prevent cheating). This allows you to come to the field, do your
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checks / test flights with telemetry, and turn the restricted mode on before the beginning of the contest on
the radio itself.
● Default channel order: Defines the order of the 4 default mixers that are inserted on channels 1-4 when
creating a new model. Set this to your preference. They can of course always be moved later, this is just a
time-saving option.
● Mode: This is your stick mode, e.g. Mode 1 for throttle and aileron on the right stick, Mode 2 for throttle
and rudder on the left stick.
SD browser
A SHORT press of the PAGE key brings up the SD card browser page:
This allows you to browse the SD card contents.
On each file or folder, pressing ENTER will bring up a contextual menu with some basic file operations
(copy/delete), as well as others depending on the file type.
Folders are organised as such:
● BMP folder: This is where you should place the 64x32, 4-bit grayscale .bmp files that you want to use as
model logos. Filenames must be 10 chars long or less (not including extension). A collection of files is
available here. Placing the cursor over a valid file in this folder will show it on the right side of the screen,
and in the contextual menu you will find an entry to assign the selected image to the current model.
● LOGS folder: This is where you will find telemetry logs if enabled. Files will be created with the same name
as the model they were saved from, with the date appended. One log file is created per day for each
model.
● MODELS folder: Model files saved by the "Archive model" command of the model selection screen will be
placed here. Similarly, models you want to reload using the "Restore model" of the same page need to be
placed there beforehand.
● SOUNDS folder: This is where voice packs need to be placed. ZIP files with the standard voice packs can
be downloaded from within OpenTX companion, or here. Extract the ZIP file to the root of the SD card, and
it will create the necessary subdirectories (e.g. SOUNDS/en for the English pack). Any file you want to
have available for the "Play Track" custom function needs to be placed within the language's directory as
well. In this folder, the contextual menu includes a preview function.
The microSD card can be formatted by selecting the relevant option in the menu that appears when pressing
MENU LONG. A confirmation will be required.
Trainer
A SHORT press of the PAGE key calls the trainer settings page:
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This page allows you to configure the trainer function for "master" use (make sure the Trainer mode in model
settings is set to Master). For each of the 4 main functions you will be able to set the mode (OFF, += for Add, := for
Replace), ratio and input channel.
Start by setting the mode for each function (the "standard" way is Replace i.e. when the trainer function is activated
the function is fully transferred to the student, Add allows both master and student to act upon the function
together). Then select the source channel accordingly to the brand/model of the student radio, and set the ratio to
100% for now. Now ensure the student radio is connected and recognised (moving the sticks of the student radio
should change the 4 numbers at the bottom of the screen) make sure all its trims are neutral, all its sticks are
centered (including throttle). Select the CAL field and press ENTER twice. The numbers should now be 0.0 or very
close.
Now move the student radio's sticks and check the numbers vary from -100 to +100. Should they reach those
values before the stick hits the end of its travel, reduce the ratio so that the throws match. Should they never reach
-100 to +100 even with full stick deflection, use the Multiplier field to increase it.
Trainer input is now configured. Note that this setting is global, because it depends on the student radio regardless
of the selected model. In order to use the Trainer function on a specific model you will need to assign the switch
you want to the "Trainer" Custom Function for that model. More about this further.
Version
This screen allows you to see the version of your currently loaded OpenTX firmware.
When reporting a bug, please be sure to include the revision number you see on the SVN line.
Diagnostics
The next 2 pages are the switch and analog diagnostics, they will show you what the firmware reads from the
radio's keys and potentiometers. This is the first place to go to if you run into issues with badly responding sticks /
pots / switches. If things are wrong here (inconsistent stick centering or end point readings, flickering value,...) then
you can be sure the problem is hardware-related and not due to wrong model setup.
The Analog page also features the battery calibration setting. It should be correct out of the box, but if not move the
cursor to the field, and adjust it so that the displayed value matches the voltage you can measure on the battery
terminals with a voltmeter.
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Calibration
This is the place where you can calibrate sticks and pots. Follow the on-screen instructions, and note that when
asked to center the sticks this includes the throttle stick and the 2 sliders. S1 and S2 pots however do not need to
be centered, only the extremes are calibrated.
Model menus
A SHORT press of the MENU key from the main views brings up the model selection screen. There models can be
selected, deleted, backed up and restored to/form SD card using the menu brought up by a LONG press on the
ENTER key. They can also be copied or moved (one SHORT press on ENTER key highlights the line, +/- create
and place a copy of the model on the desired slot, while two SHORT presses create a dotted outline where +/-
simply move the selected model to another slot.)
Model setup
A SHORT press of the PAGE key brings up the basic model setup page:
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● Model name: Self-explanatory... Change letter with +/- keys, go to the next with ENTER SHORT, or press
ENTER LONG to capitalize the current letter before switching to the next.
● Model image: There you can select a 64x32px, 16-grayscale .bmp file located in the BMP folder of the SD
card as your model logo. To be able to preview the images in the folder, use the SD Browser.
● Timers: There are 2 fully programmable timers, that can count either up or down. If the value is set to
00:00 they will count up from 0, if not they will count down from the preset value. The trigger is set using
the field next to the timer value, ABS counts up all the time, THs runs whenever the throttle stick isn't at
idle, THt starts the timer the first time throttle is advanced, TH% counts up as a percentage of the full stick
range. Persistent, if ticked, means the value is stored in memory when the radio is powered off or model is
changed, and will be reloaded next time the model is used. Minute call will beep / say the time every full
minute. Countdown can be set to Silent, Beeps or Voice. With Silent selected, the timer will be silent until
zero is reached. When zero is reached, a single beep will be played. With Beeps selected, beeps are
played at 30 seconds, 20 seconds and from 10 seconds down to zero. When the timer reaches zero, a
slightly longer beep will be played. And with Voice selected, ‘30 seconds’ is played at 30 seconds, ‘20
seconds at 20 seconds, 10,9,8,etc down to zero and finally a beep at zero.
● Extended limits allow setting servo movement limits up to 125% instead of 100%.
● Extended trims allows trims to cover the full stick range instead of +/-25%. Be careful when using this
option, as holding the trim tabs for too long might trim so much as to render your model unflyable. The
"Reset" item will reset all trims (for all flight modes).
● Trim step sets the precision of trim clicks. Exponential means very fine steps close to the trim center, but
larger ones the farther you get from center.
● Throttle reverse: Ensures correct operation of throttle-based timers and functions for people who like
having full throttle with the stick down.
● Throttle source defines what triggers the THx functions of the timers. It's common to set it to the throttle
channel instead of the stick, so that throttle cut or other modifiers are taken into account.
● Throttle trim: IC engine mode, where trim only affects the idle part of the throw without touching the full
throttle point.
● Throttle Warning: Will warn you if the throttle stick is not at idle when the radio is powered up or a model is
loaded.
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● Switch warning: Defines whether the radio requests the switches to be in predefined positions on power
on/model change. To set them, arrange your switches the way you like, and press ENTER LONG.
● Center beep: Makes a beep when the selected control(s) pass the center point.
● Internal RF:
○ Mode: Transmission mode of the internal RF module (OFF, D16, D8, LR12).
○ Channel range: Choice of which of the radio's internal channels are actually transmitted over the
air.
○ Receiver no (D16 / LR12 only): defines the behavior of the receiver lock function. This number is
sent to the receiver, which will only respond to the number it was bound to. By default this is the
number of the model's slot when it is created. It can however be changed manually, and will not
change if a model is moved or copied. If manual setting or a copy/move operation results in 2 or
more models on the radio having the same number, a warning popup will show up. It is then up to
the user to determine if this is the desired behavior or not and change if required.
○ Bind and range check fields get activated by a press of the ENTER key. The radio will beep every
few seconds to confirm. Range check will display a popup with the RSSI value to evaluate how
reception quality is behaving.
○ Failsafe mode (D16 / LR12 only): Allows choosing between simply holding the last received
positions, turning off pulses (like old PPM MHz receivers), or moving the servos to custom
predefined positions. For custom positions a SET field will call the failsafe settings page, where
the position can be defined separately for each channel. Select the desired channel, press ENTER
to get in edit mode, move the control to the desired position, and press ENTER to save. In D8
mode this field is hidden, failsafe needs to be set on the receiver as described in the receiver's
manual.
● External RF:
○ Module type: PPM for generic modules, XJT (same operation modes as above), DSM for
Spektrum “hack” modules made using these instructions. Note that the Orange DSM and
Spektrum DM9 modules both need PPM.
○ Channel range: same as for internal module.
○ Receiver no, Bind, Range check (when module type is XJT): Same as above.
○ PPM Frame (when module type is PPM): Allows setting the frame length, pulse length, and
polarity of the PPM frame. The frame length is automatically adjusted to a safe value when the
number of transmitted channels is changed. Advanced users can still adjust it afterwards if
necessary.
○ Failsafe mode: When module type is XJT, same as above.
● Trainer mode: Master or slave, this setting defines which way the trainer port works. An icon is shown in
the main view when the cable is inserted showing which mode is in use. In Slave (output) mode, the
channels that should be sent and the PPM frame parameters are customizable just like for External RF ->
PPM.
Helicopter setup
A SHORT press of the PAGE key will bring up the helicopter CCPM head mixer page. This page allows setting a
swashplate type, and limiting the control authority through the Swash Ring setting.
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The inputs of this mixer are the Ail and Ele sticks, plus the virtual channel selected in "Collective source". This
channel would see entries added on the MIXER page for one or more pitch curves.
The outputs of the CCPM mixer are CYC1, CYC2 and CYC3, which need to be assigned on the MIXER page to
the channels you will connect your servos to.
Note that the settings made here have no effect unless you are using those CYC1, CYC2 and CYC3 sources. A
multirotor or flybarless helicopter which uses onboard computers/mixers will NOT use them.
Flight modes
Next up is the flight modes screen.
8 flight modes plus the default one are available for use. Each of them can be named, has a selectable activation
switch (physical or logical), a trim selection array (R, E, T, A when shown means the mode has its own trim setting
for that control, but each can be changed to a number from 0 to 9 and thus use the same value as the specified
mode), and slow up/down parameters for smooth transitions between modes.
The priority of the flight modes is such as the first FM of 1-8 that has its switch ON is the active one. When none
has its switch ON, the default FM0 is active.
Inputs
The next screen allows setting one or more input formatting rules to each stick axis. This is the first step of the
control chain - where you define the amount of control authority you want on each stick.
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As many lines as required can be assigned to each stick (LONG press ENTER brings up a popup menu to
insert/delete lines), and again the first one that has its switch on (starting from the top) will be the active one. This
is commonly used to create dual, triple,... rates. A name can be defined for each entry, as well as the rate and
exponential ratio. A curve (built-in or custom) can also be used instead of the "simple" exponential function.
The Modes line allows to choose in which flight mode(s) (highlighted numbers) that line can be active. If the current
mode is not selected, turning on the switch will not activate that formatting line.
The Side parameter limits the effect of that formatting line to only one side of the stick. A summary of the selected
modes for each line is shown on the main screen.
Mixer
The next page is where the actions on the controls will be mapped to servos. OpenTX does not have any
predefined mixing functions that relate only to a particular model type or situation, it rather gives you a blank
canvas you can build upon. The key to configuring a model on OpenTX is not to think about "activating the delta
mix" like on certain radios, but rather to think about what you want your control on the model to do in response to
an input on the radio's controls. The mixer is where all that "logic" gets entered.
The various channels are outputs, for example CH1 being the servo plug #1 on your receiver (with the default
protocol settings). A channel without a mixer line will just center a servo that would be connected to it.
Each mixer line connects one input to the channel it's on. Inputs can be:
● The 4 stick axes
● The 4 pots and sliders
● The heli mixer outputs (CYC1-3)
● A fixed value (MAX)
● The 8 physical switches
● The 32 custom (logical) switches
● The trainer port input channels (PPM1-8)
● Each of the radio's 32 channels, which allows using channels as a virtual functions for clarity (mix several
inputs into one reuseable function, that can then be assigned to one or more channels). Note that the
settings of the SERVOS page are NOT taken into account there.
All inputs work on a -100% to +100% basis. Sticks, pots, channels, CYC sources, trainer inputs will vary
proportionally within this range. 3-position switches will return -100%, 0% or +100%. 2-position switches (and logic
ones) will return -100% or +100%. MAX is always +100%.
If you want the servo connected to the #2 plug of your receiver to be controlled by the elevator stick, you will simply
create a mixer entry on CH2 with Ele as source. Easy enough!
There can be as many lines as needed on each channel, and the operation between each line can be selected. To
create a new line, you would LONG press the ENTER key, and select insert before/after. By default all the lines on
a same channel are added together, but a line can also multiply those before it, or replace them.
For clarity, each line that is currently active and contributing to the channel's output will have its source displayed in
bold. This can be very handy when many are present and to check switch functions.
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For each mixer line, several parameters are available:
● A name can be entered for convenience
● The weight (in %) of the input can be set. This sets how much of the input control has to be mixed in. A
negative value inverts the response.
● An offset on the input value can be added.
● A trim can be used, for sticks this is by default the trim associated to the stick, but can be chosen to be one
of the other trims (for cross-trimming for example) or disabled altogether. For other inputs the trim defaults
to OFF, but can of course be set to one if required.
● Either a differential value can be set (reduces response by the specified percentage on one side of the
throw) or a curve (built-in or custom) can be assigned. When a custom curve is selected, a press of the
MENU key will bring you to the curve editor.
● The modes the mixer line is active in can be selected (see D/Rs).
● A switch (physical or virtual) can be used to activate the mixer line.
● A sound warning (1, 2 or 3 beeps) can be set to play whenever the line is active.
● The Multpx setting defines how the current mixer line interacts with the others on the same channel. "Add"
will simply add its output to them, "Multipl" will multiply the result of the lines above it, and "Replace" will
replace anything that was done before it with its output. The combination of these operations allows
creating complex mathematical operations.
● Response of the output can be delayed and/or slowed down with regard to the input change. Slow could
for example be used to slow retracts that are actuated by a normal proportional servo. The time is how
many seconds the output will take to cover the -100 to +100% range.
As a little example, if you wanted to add some compensation on the elevator channel when you increase throttle,
you would go through a simple path:
● What's the control surface I want this to act on? Elevator, which is connected to CH2.
● When do I want it to move? When I move the throttle stick, in addition to whatever would already be
present (usually the elevator stick).
So you would simply go on CH2, and insert a new line with Thr as source. Type would be Add as the
compensation needs to be added to the "normal" elevator response. As the required compensation is likely small,
you will dial in a small weight, maybe 5%. On the ground with motor disconnected, you will check the elevator
compensates in the correct direction. If not, you'll invert the weight to -5%.
You could then assign a switch, in order to be able to activate/deactivate it in flight to see if the amount of
compensation is actually appropriate. If the correction is more complicated, you might want to assign and create a
curve that matches what's required.
Mixer Functions
TODO
(X>0) only operates on the plus side of the sick and (x<0) works on the -ve side.
You could use these for setting differential or complicated ailerons.
([x]) moving the stick from centre either way results in an of 0/+100
I have used this output for someone's setup, but can't remember why.
(F>0) results in full travel to the plus side as soon as the stick is moved to the plus side and has no output on the
-ve side.
(F<0) it's the opposite of (f>0).
([f]) as soon as a stick is moved the output goes full travel to the side the stick is moved towards.
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Many of these are "legacy" functions from er9X or even earlier.
They can be used to generate things like differential, which was added later.
They would still be used to generate things like knife edge mixes where you want the correction to be the same for
both stick directions
simple example
CH02 (+100%)[i]Ele
(+10%)[i]Rud noTrim Curve(|x|)
Servos
The SERVOS page is the interface between the setup "logic" and the real world with servos, linkages and control
surfaces. Up to now, we have set up what we want our different controls to do, now is the time to adapt that to the
mechanical characteristics of the model.
For each channel, we can define:
● A name, that will be shown on the mixer screen when the cursor is on a line belonging to that channel, on
the channel monitor and on the failsafe settings page.
● An offset or subtrim.
● Low and high limits. These are "hard" limits, i.e. they will never be overridden, so as long as they are set
so that your servo never forces, it really never will. They also serve as gain or "end point settings", so
reducing limit will reduce throw rather than induce clipping.
● Servo reverse.
● Center adjustment. This is similar to subtrim, with the difference that an adjustment done here will shift the
entire servo throw (including limits), and won't be visible on the channel monitor.
● Subtrim behavior: When set to default, adjusting subtrim will only shift the center of the servo throw. Given
a -100% to +100% order from the mixer, the servo will still move exactly between the lower and upper
limits, without clipping or dead band. This introduces a different stick to servo movement relation for both
sides of the stick. Depending on the situation it can be either convenient or problematic, so the = setting
has been added to change subtrim effect to rather shift the servo throw "symmetrically". A full throw order
from the mixer can now be clipped by the limit that is on the same side as the subtrim, while on the other
side the servo will not reach the limit anymore. That way on both sides of the stick a given stick movement
always results in the same servo movement. Typically using the default mode allows for faster setup of
servos that are driven by a single control input, while = is required to keep correct response of control
surfaces using differential and/or mixing several inputs together. The = mode typically requires reducing
D/R so that a margin is left between full "control" throw and the defined limits.
The following diagram illustrates the respective behavior of both subtrim modes and how Center adjustment
compares to them:
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