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Open Source Firmware
ErSky9x Explained
for the Turnigy 9XR Pro
[This version should be final except for links on the last two pages.]
This manual is based on version r204 of the
Ersky9x firmware, issued in May 2014. For more
information, see page 44.
Screen shots show a pre-production transmitter.
Ersky9x Explained – version 1
ErSky9x Explained
Introduction ................................................................................................................................ 1
Navigating in ErSky9x ................................................................................................................ 2
Button Navigation ................................................................................................................... 2
Navigating Between Pages. ................................................................................................... 2
Navigation in a Menu ............................................................................................................. 3
Home Pages .......................................................................................................................... 3
Statistics Screens .................................................................................................................. 6
Radio General Settings .............................................................................................................. 7
Radio Setup (page 1/11) ........................................................................................................ 7
Boot Reason (page 11/11) ....................................................................................................12
SD Card Stat (page 10/11) ....................................................................................................12
Calibration (page 9/11) ..........................................................................................................12
ANA (Analog Inputs) (page 8/11) ..........................................................................................13
DIAG (Diagnostics) (page 7/11) ............................................................................................13
Date-Time (page 6/11) ..........................................................................................................13
Version (page 5/11)...............................................................................................................14
Trainer (page 4/11) ...............................................................................................................14
Memory Stat (page 3/11).......................................................................................................16
Radio Setup 2 (page 2/11) ....................................................................................................16
Model Setup Menus ..................................................................................................................17
ModelSel (Model Select) .......................................................................................................17
Setup XX (page 1/13)............................................................................................................19
Heli Setup (page 2/13) ..........................................................................................................23
Modes (Flight Modes) (Page 3/13) ........................................................................................24
Expo/DR (page 4/13) ............................................................................................................24
Mixer (page 5/13) ..................................................................................................................26
Limits (page 6/13) .................................................................................................................31
Curves (page 7/13) ...............................................................................................................32
Custom Switches (page 8/13) ...............................................................................................33
Safety Switches [and Voice Switches] (page 9/13) ................................................................35
Telemetry (page 10/13) .........................................................................................................37
Telemetry 2 (page 11/13) ......................................................................................................39
Templates (page 12/13) ........................................................................................................41
Global Variables (page 13/13) ...............................................................................................43
Scalers ..................................................................................................................................43
Conclusion ................................................................................................................................44
Further Information ...................................................................................................................45
9XR Pro Ersky9x Explained 2014-05-13
Ersky9x Explained – version 1
This manual provides a detailed overview of the ErSky9x open source firmware used in the Turnigy
9XR Pro transmitter. The great flexibility of this programming system means that there is a lot that
needs to be described. You might see this as intimidating, but you don’t need to learn everything
before you can enjoy flying with this transmitter. That’s why we have provided a separate and
simpler guide: First Steps with ErSky9x. We recommend you read that first to get the overall picture
and to learn enough to get you flying. Also be sure to read Introduction to the Hardware (see
“Further Information” at the end of this manual).
We also recommend that you make use of the available RC forums and especially, which is dedicated to the various open source RC firmwares including this one.
There you will find enthusiasts, including the program and hardware developers, ready to help you
get the most from this amazingly advanced and still evolving RC software. While there, you should
consider making a donation for their efforts.
The features of the 9XR Pro transmitter running ErSky9x firmware include: 32 model memories plus
an unlimited number on your computer; up to 24 channel operation; potential for telemetry
communication and display on the screen; spoken announcement of alarms, switch settings and
telemetry values; completely free mixes allowing almost unlimited programming of controls and
switches; 5 point and 9 point custom curves; assignment of any channel to any function. The radio
also supports an SD card for the storage of audio, firmware, telemetry logs and manuals to which
this one belongs. ErSky9x supports Bluetooth communication if the required hardware is added to
the circuit board. It also provides USB access to the computer-based Eepskye program, which
allows updating the firmware, model memory and SD card. Eepskye also simulates the sticks,
sliders and switches on the radio, both for programming and for developing model settings. Easy
updating of the firmware allows you to benefit from the improvements continually being developed.
The combination of extremely flexible programming and a powerful new main board designed by Sky
North results in an inexpensive transmitter that is among the most capable available today.
Ersky9x Explained – version 1
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Navigating in ErSky9x
Button Navigation
The transmitter has six input keys: a cruciform set of RIGHT/LEFT/UP/DOWN keys, plus contextual
MENU and EXIT keys.
The RIGHT/LEFT/UP/DOWN keys to the left of the screen move the cursor or pages in the
appropriate directions. Note that short presses and long presses will produce different results.
For example, when you turn your transmitter on it will start at one of five 'Home' pages. Short
presses of the UP and DOWN keys will take you to different home pages. Each press of the key
brings a new screen, eventually taking you back to where you started. Whichever screen you last
used will be the home screen that appears when you next switch the transmitter on.
If, however, you press the UP key for about half a second (i.e., long UP) you will be shown a screen
which has information about the Battery and related matters (see page 6).
Confused? Don’t worry, all this gets quite easy once you have handled the transmitter for a short
Navigating Between Pages.
The home pages form a central core from which you can go right, left, up or down to access sets of
pages which have similar functions (see diagram below).
A long LEFT press takes you to the Radio Setup section where short presses RIGHT or LEFT allow
you to cycle through the 11 pages.
A long RIGHT press takes you to the 14 pages of the Model Setup section. A long UP press from the
home pages takes you to three Statistics pages as you can see in the diagram above. And a long
DOWN press takes you directly to the Telemetry pages.
The Telemetry pages can also be accessed from the Home pages by short presses of DOWN or UP
a number of times until the first telemetry page shows. These pages are recognizable because they
do not have the trim position graphics along the bottom and edges of the screen.
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Once on a page, short presses of LEFT and RIGHT step through the various items found there, such
as physical and custom switches.
Navigation in a Menu
Navigation in a menu is straight forward: The UP/DOWN/RIGHT/LEFT keys will navigate between
editable fields, or lines of fields depending on the screen.
Pressing MENU will enter the edit mode. In this mode, RIGHT/LEFT change the value, while MENU
or EXIT validate the input and return to navigation. If there is only one value on a line to be edited,
the LEFT and RIGHT keys change it directly without pressing MENU.
A short press on EXIT goes back to the previous navigation level, but a long press goes back to the
home page where you started. To return to the previous page, long press the MENU button.
In edit mode, a shortcut is available to reverse the sign of a value. With the cursor on the value,
press LEFT and RIGHT keys together and the sign will change from positive to negative or vice
versa. (This works even with the cruciform key arrangement, as the keys register close enough
together for the radio to recognize the shortcut.)
Home Pages
There are five Home pages, four of which show the same basic information in the top part of the
screen: model name, transmitter battery voltage, timer value, timer switch identity, and trim
increment setting. Trim position graphics are shown on the sides and bottom of the screen. The fifth
Home page shows telemetry.
Home Page 1 (Stick and Pot Positions)
In the first Home page view, the lower half of the screen shows a graphical representation of stick
and potentiometer positions. A list of the switches shows those in the ‘up’ position in normal text,
while those in the 'down' position are presented in white letters on a dark background (i.e.,
reversed). In other words, this screen shows the inputs to the processing.
In the upper half of the screen, the transmitter voltage is displayed in large print, along with the trim
increment type, here ‘Med’ (see page 20). The current value of Timer 1 is also shown in large print,
along with the switch used to activate it, here ‘THs’ (see page 20). In addition, the current Flight
Mode will be displayed if it is other than the default FM01.
Home Page 2 (Graphic Servo Outputs)
In the second Home page view (short press down from the previous screen), the upper part of
the screen is identical to Home Page 1, while the lower half of the screen shows in bar graph
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form the channel outputs. These bars reflect the outputs resulting from the programming for the
particular model processing the inputs of the sticks, pots and switches.
Note that just above the channel output graphic is a bar showing which channels are being
displayed. A short press of the RIGHT or LEFT key changes the channel view from the first set of 8
channels (1-8) to the second set (9-16) and then to the third set (17-24). With the necessary
hardware, the transmitter is capable of controlling 24 channels.
Warning: It’s easy to give a short right press inadvertently and display channels not being used on
your transmitter. This can be very confusing.
Home Page 3 (Numeric Servo Outputs)
In the third Home page (short press down from the previous screen) the lower half of the screen
shows the channel outputs in digital form from -100% to +100%.
Again, the bar shows which channels are being displayed (here 1-8). The upper part of the screen is
identical to the previous screens.
Home Page 4 (Timers)
In this Home page the lower half displays just the Timer 2 reading in bold type for easy visual
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Home Page 5 (Telemetry Series)
In the fifth Home page (short press down from the previous one) the screen shows various sets of
telemetry data. These may include Global Positioning System (GPS) data, voltage, temperature, rate
of climb, battery capacity used or other information, depending on what sensors you have installed in
your model.
A long press of the MENU button will reset the maximum altitude and maximum speed readings to
zero. For further information on telemetry see page 37.
A short press of the RIGHT or LEFT key will cycle among the five Telemetry screens, which you can
adapt to suit your requirements. Consequently, the information in the screens may vary from what is
shown below.
The next page (not shown) has the upper half as described before and the lower half a customizable
value, which may be a timer or a telemetry value or other variable.
The last Telemetry screen provides for information specific to the DSM protocol and is intended for
use with a DSM telemetry transmitter module. It only appears when DSM2 or DSMX operating mode
is selected in the Model Setup Screen (1/13).
A short press of the UP or DOWN key will take you back to the Home screens and allow you to cycle
through them.
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There are various operations using the EXIT button. If the timer is beeping, a quick press of the EXIT
key resets it and stops the beeping. If you are on a telemetry screen, a quick press of the EXIT key
resets the telemetry.
LONG EXIT resets both TIMER 1 and telemetry.
Statistics Screens
1. Battery Screen
From the Home pages, a long press of the UP key brings up a screen where the battery details, time
and ‘CPU temperature’ are shown. (currently, the temperature reading is typically as much as 10ºC
too low, as shown).
The mAh reading shows the battery capacity used since the last reset, normally after charging the
battery. To reset the number to zero, long press the MENU key. To adjust date or time, go to page
6/11 of the Radio Setup screens.
2. STAT Screen
A short press UP from the Battery screen brings a statistics screen whose main feature is a graph of
throttle position versus time. It also shows the periods for which the timers have been active and
total time the transmitter has been on.
3. STAT2 Screen
Another short press brings a screen which shows the ‘tmain' in milliseconds (the maximum time
taken to run the main menu loop in the firmware – this is mainly for the developers).
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The screen also shows information relating to the BIND reply if a DSM module is used and 'BT reply'
(Bluetooth), if the necessary hardware is installed. Another short press of the UP key brings you
back to the home page from whence you started.
That’s it for navigation among the various Home, Telemetry and Statistics screens that mainly
display data. Now we explore the pages of Radio Setup that allow us to set the basic parameters for
how the transmitter operates.
Radio General Settings
From the Home pages, a LONG press of the LEFT key yields the radio setup menu.
Navigation among the pages here is as follows. The UP and DOWN keys move the cursor to
highlight values that may be edited. A short press of the MENU key will cause the cursor to flash and
allow the RIGHT and LEFT keys to change the values or options in that field. A short press of the
EXIT key will stop the cursor from flashing (i.e., will exit Edit mode) and allow navigation up or down.
We start with page 1/11, as this contains many of the most important settings and is the first we
come to by pressing LEFT. After that we will continue to press LEFT, which takes us through the
remaining pages in reverse order. (We could equally well press RIGHT and view them in nominal
Radio Setup (page 1/11)
Owner Name
This is the only field in Radio Setup where the entry method is different to the above description.
Choose a space where a letter is required and press MENU to highlight it. When the UP or
DOWN key is pressed the following are shown in sequence: a blank space, upper case letters,
lower case letters, numerals, '_' and '- 'and '.'. When you have the correct letter or numeral in
place, press MENU or EXIT to allow you to move left or right. Highlight the next space, press
Ersky9x Explained – version 1
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ENTER and select the character. And so on. The name you enter will show on the opening
screen at startup if ‘Splash Name’ is ON (see below).
There are six options available for the duration of the beeper sound: extra-long, long, normal,
short, extra short, no-key and quiet. As each option is selected the beeper makes the
corresponding sound. The NoKey selection eliminates the beeps when editing but allows alarms
to sound. Quiet means no sounds or alarms at all.
Contrast: Screen contrast setting
The higher the value the darker the screen.
Battery Warning
Sets the voltage at which a warning message will be announced, alerting you to “low battery”.
The voltage you choose depends on the minimum safe level for the battery size and type you
have installed in the transmitter. The transmitter will work down to about 6 volts, but you need
time to land and your battery may have a much higher minimum safe voltage (e.g., about 9.3v for
LiFe chemistry and up to 11v for LiPo). See the manual Introduction to the Hardware for advice
on batteries and settings.
Inactivity Alarm:
This reminds you to turn off the transmitter. If the transmitter is left turned on with no movement of
the sticks for the period of inactivity set here, this alarm will sound. Values can be from 1 to 250
minutes. To reset the timer simply move one of the sticks. To disable the alarm, set the value to
Filter ADC: Analog to Digital Conversion
The ARM processor in the 9XR Pro is 12-bit, giving 4096 resolution (compared to 10-bit, 1024
resolution for the 9X and 9XR AVR processors). Since the Ersky9x firmware uses 2048
resolution, conversion is necessary.
There are three options for the analog to digital conversion:
SING: Single conversion. This is the fastest process, simply reading the value once and dividing
by 2 to achieve the resolution required by the firmware.
OSMP: Oversampling. This option averages four consecutive values to smooth servo response.
It’s only slightly slower than SING and is the best choice for most users.
FILT: Filtered. This option averages over a longer time to minimize conversion noise and thereby
reduce servo jitter. It will, however, increase latency by about 10 msec.
Throttle Reverse
Only if you fly with the throttle “backwards” (i.e., with idle away from you and full throttle towards
you) should you set this to ON. It will also reverse the throttle warning on startup.
Minute Beep
Set this ON if you want a beep or announcement to sound every minute during timer operation.
Beep Countdown
Set this to ON if you want the timer to sound beeps or announcements during the last minute of
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Flash on Beep
Set this ON if you want the screen to flash every time the transmitter beeps.
Light Switch
The back light can be set to turn ON via any of the transmitter physical switches (RUD, ID0, ELE
etc.) or any of the virtual switches (SW1, SW2, etc.).
Light Off After
This may be set as OFF or in 5 second intervals up to 600 seconds.
Light on Stick Movement
This may be set as OFF or in 5 second intervals up to 600 seconds.
Splash Screen
This may be set to ON or OFF. The splash screen is displayed at start up with an announced
welcome message. An alternative is to have the model name announced or some music played.
The splash screen and the announcements on start-up can be customized using voice
commands as explained in a different part of this manual.
Splash Name
This may be set to ON or OFF. If ON, the name set in Owner Name above will be shown on the
splash screen.
Throttle Warning
If ON this will show a warning when throttle is not at idle when the transmitter is turned on. The
transmitter will not output a signal until such alerts are cleared.
Alarm warning
This will give you a “heads up” if the beeper is silent. If ON and the beeper is set to '0' (Quiet) you
will receive a warning on startup.
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The choice here is POT, STICK, BOTH or NONE. Pot Scroll means that two of the
potentiometers can be used for control of the cursor when a menu is onscreen. The right pot
scrolls the cursor up and down to choose the item, while the left pot adjusts the value. Likewise,
Stick Scroll enables the elevator/rudder stick (mode 1) or elevator/aileron stick (mode 2) to move
the cursor in a similar way.
Note that Stick scrolling doesn’t work in menus where the sticks themselves are involved, such as
the ANA page, the Calibration page and the Expo/DR page. Likewise, Pot scrolling may not
always work; for example, you can’t use it to choose an action on the Model Select page. In these
situations, you should use the navigation keys, which always work. Normally, stick/pot scrolling
will work again after the a few uses of the navigation keys. If not, you may have to turn scrolling
off and back on again.
Internal FrSky Alarm
FrSky telemetry modules, when used with D-series receivers, produce their own Received Signal
Strength Indication (RSSI) alarm sounds (see module instructions for details). Where RSSI
alarms (either voice or beeper) are set in the transmitter itself, the module alarms are normally
turned OFF, as shown in the picture below. Generally you don’t want to have the module beeping
as well as the transmitter!
Cross Trim
This allows you to swap the trim buttons for each stick swapped to the opposite side of the
transmitter, i.e., Elevator trim is next to the throttle stick. This can make trim adjustment in flight
easier, particularly for Mode 2 fliers, for whom it allows aileron and elevator trim to be adjusted
with the left hand (for another way to assist in the trimming of a new model, see Trim Switch
under Model Setup, page 21).
The options currently available are French, German, Norwegian and Swedish.
Channel Order
This setting determines the sequence of the first four channels that will be used in setting up a
new model or applying a template. This is the order in which the outputs will be available from the
receiver. Popular channel orders include TAER (used for DSM receivers, which typically provide
throttle failsafe only on channel 1) and AETR (used by many manufacturers). Note that Ersky9x
provides complete flexibility in selecting channel order.
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Mode (i.e., stick mode)
Choose the Mode setting (1, 2, 3 or 4) to suit your preference and/or match local practice. Mode 1
(throttle and aileron on right stick, elevator and rudder on left) and Mode 2 (elevator and aileron
on right stick, throttle and rudder on left) are by far the most popular stick configurations around
the world. Less common are Modes 3 and 4, which are similar to modes 1 and 2 respectively
except that they have aileron control on the left and rudder on the right.
To change mode in the Radio Setup page, move the cursor to the number below ‘Mode’, press
MENU and use the arrow keys. This will change the stick assignments shown below the stick
function diagrams.
The physical stick arrangement of the gimbals must match the chosen mode. Specifically, the
throttle stick is normally non-centering, using friction or a ratchet to hold its position, while other
axes use a spring to return the stick to center. Normally the transmitter is purchased in the
desired mode 1 or 2 physical configuration, but this can be changed by the user (though doing so
may void the warranty).
Changing the stick mode requires removing the back of the transmitter, partly disassembling each
stick unit and interchanging the spring centering mechanism on the vertical axis of one with the
friction mechanism on the other. A video showing the process in detail can be found on the
Internet.1 Alternatively, a pair of stick assemblies in the appropriate mode (1 or 2) can be
purchased inexpensively and substituted relatively easily for the existing sticks.
The other feature available in this area of Radio Setup is to be used ONLY if the transmitter
gimbals are upgraded to a different type. Doing so may require that the operation of one or more
sticks be reversed to agree with the direction of the corresponding trim switches. To use this
capability, move the cursor to the stick function diagrams, press MENU and highlight the axes to
be reversed. To change back to normal stick directions, press LEFT repeatedly. Do not use this
feature to achieve servo reversal.
That’s the end of Radio Setup, the longest screen of all. Fortunately, it isn’t necessary to change
these settings very often, and most can be left on their default values.
Now to other pages that set parameters or display information, starting at the last.
11 ... redirect=1
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Boot Reason (page 11/11)
With the cursor on the top line of the previous screen, a short LEFT press moves to a screen which
shows how the transmitter was last started (normally ‘Power On’). If you have an unexplained startup or shut-down, this information may help in troubleshooting.
SD Card Stat (page 10/11)
Another short press of the LEFT key brings up this screen showing information about usage of the
memory on the Micro-SD card.
Calibration (page 9/11)
LEFT again brings up the screen that allows the firmware to recognize the limits and centering of the
sticks, as well as the limits of the three pots (potentiometers).
Just follow the instructions on-screen, pressing MENU to start, then centering the sticks and
pressing MENU again. Finally, move the sticks to their full extent in all directions (don’t press hard
against the stops) and twist the pots through their full range. Press MENU again and you’re done.
NOTE: It is essential to calibrate the transmitter initially and whenever there are any changes that
could affect the stick or pot outputs (e.g., replacement of a stick assembly). With the 9XR Pro (unlike
the 9XR) the calibration data are stored in General Settings, separate from model memories.
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ANA (Analog Inputs) (page 8/11)
Another short press of the LEFT key brings up a screen that shows the analog inputs (sticks, pots
and battery voltage) in hexadecimal format to save space.
A1..A4 are the gimbals (sticks). A5..A7 are the pots. A8 is battery voltage. Values range from 0 to
0x7FF (0 to 2047 decimal).
If you highlight the battery voltage, pressing LEFT/ RIGHT will adjust the value, enabling you to
calibrate the reading to equal what you measure with a voltmeter at the battery itself.
This screen also shows the current being used by the transmitter in milliamps (mA).
DIAG (Diagnostics) (page 7/11)
Short pressing the LEFT key brings up a screen that shows the position of every physical switch as
seen by the transmitter. If a switch is OFF (up or back), a zero is shown. Note that if, for example, a
switch has become loose, this page will tell you if it is mounted the right way up. The action of the
trim switches is also shown (not the trim settings themselves).
Date-Time (page 6/11)
This is the screen where the transmitter’s real-time clock is adjusted to show the current date and
time. Use the UP/DOWN keys to navigate and the RIGHT/LEFT keys to adjust the values. Note that
the transmitter uses the 24-hour clock.
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The calibration (Cal) value may be changed to correct inaccuracies in the clock.
Version (page 5/11)
This screen shows the version information for the current firmware:
SVN: Name of the current release in the Subversion management system.
VERS: Version number used by the developer.
DATE: Compile date for the current firmware.
TIME: Compile time for current firmware.
MOD: Main circuit board model
Since ErSky9xr is open source, anyone who has problems is welcome to log on to the internet
forums and seek help. When you seek a solution, please use the release and version numbers
shown in this screen (here r203, V.3579).
Your participation is what helps make the firmware better.
Trainer (page 4/11)
This menu is used when the transmitter is functioning as the Master in a “buddy box” arrangement
(the Master is the transmitter held by the instructor and is the one to which the model’s receiver is
bound). The menu allows the PPMin (trainer) inputs coming (by cable or wirelessly) from the student
(Slave) transmitter to be matched to the channel setup of the Master transmitter. The channel order
of the Slave transmitter and the Master do not need to be the same, provided this screen is used to
match them up correctly. The slave transmitter does not have to be a 9XR Pro: compatible
transmitters include the 9XR, 9X and Spektrum. Transmitters such as Futaba can also be used but
may require special cables.
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Transfer of control to the student transmitter for a given channel is done by activating the switch
shown in the last column. Normally this would be TRN (the momentary toggle switch) for all
channels, though sometimes instructors prefer to transfer control selectively with separate switches
for some channels. When the Trainer Switch is held ON, PPMin from the Slave transmitter is
substituted for input generated by the Master transmitter itself and the student has control of the
model. All the mixes on the Master Tx are applied to the student inputs. This includes, for example,
expo or delta wing (elevon).
The ‘mode’ column selects how PPMin is used when the Trainer Switch is activated:
off Channel unused. No input from student stick
+= Add student stick value to instructor stick value (sometimes used for training)
Replace instructor stick value with student stick value (normal training setup)
The ‘%’ entry applies a weighting to the PPMin value from -100 to +100. Use -100 to reverse the
input. Values closer to 0 reduce the student`s control sensitivity.
The ‘src’ entry selects the PPMin channel for the function. In this example, the buddy box uses the
Spektrum/JR channel order of TAER, while the master uses RETA.
The ‘sw’ entry selects the switch used to activate trainer operation, normally TRN.
Multiplier: Adjusts PPMin values by a factor from 1.0 to 5.0. Normally left at 1.
This is used to raise the incoming signal level if it is too low for the 9XR Pro.
Cal: Center calibration for first 4 PPMin values.
Allows you to calibrate the mid-point for channels 1 to 4. Highlighting ‘Cal’ and pressing MENU
will adjust the inputs from the slave to match the master.
NOTE: There is an option under Model Setup to enable or disable the trainer function for that model.
If you do not need a model to support trainer mode you may disable the function and use the trainer
switch for something else (see page 21).
While a trainer setup normally uses only the first four channels, all PPMin values are available to the
mixer if required.
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Memory Stat (page 3/11)
This page gives the hexadecimal address for the start and end of each model in memory.
Radio Setup 2 (page 2/11)
This page deals with a number of additional settings.
This value may be set from 0 to 23. The volume of the beeps as you change the setting shows
the new value. Note that within Model Setup, further control of volume can also be assigned to
one of the three pots (P1, P2, P3) or a Global value (GV4 to GV7).
Speaker Pitch
Values from 1 to 100 may be set. The pitch varies one tone up for every five value increments.
Haptic Strength
Values from 0 to 5 may be set. This parameter determines the strength of the vibration.
This refers to the screen brightness when the backlight is switched on. Values from 0 (fully dark)
to 100 (very bright) may be set.
Capacity Alarm
When the battery capacity used since last reset reaches this value an alert message will be
announced. Battery capacity used may be viewed and reset on the Battery screen (one long
press UP from any of the Home screens).
Bt Baudrate
Speed setting for Bluetooth communications (Bluetooth requires additional hardware).
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Rotary Divisor
The amplification of a rotary encoder may be set here. The range of values is 1,2, and 4. This
value depends on the make of the encoder. A rotary encoder is not included in the 9XR Pro but
can be added as a DIY project.
Stick Gain
This is only needed if another type of stick gimbal, such as Aurora 9, is fitted to the transmitter.
‘LV’ means Left Vertical, etc. If necessary, individual sticks can be reversed in the Mode section
of the Radio Setup menu.
Model Setup Menus
In the first screen of the Model Setup menus, all the 32 memory slots models are listed and any
models that have already been created are shown. Once a model is selected, a series of screens
defining its characteristics can be accessed.
ModelSel (Model Select)
Press LONG RIGHT from the Home pages to reach the Model Select screen. On this screen,
models stored in the transmitter’s EEPROM memory are listed and can be selected, copied, moved,
or deleted. In addition, individual models can be backed up to the Micro-SD card and subsequently
restored to the transmitter.
Once a model slot has been highlighted, SELECT, COPY, MOVE, DELETE and BACKUP
commands become available, as shown below. Move the cursor using the UP or DOWN key and
pick the option by pressing the MENU key.
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Active Model
An asterisk next to the model number indicates that this is the currently active model. Only the active
model can be edited.
To SELECT a model or memory slot, highlight it, press MENU, choose SELECT and press MENU
again to make it the active model.
Press short RIGHT to enter the first of the Model Setup pages for the chosen model.
Don’t be surprised if you see an ALERT screen telling you that switches need to be moved to safe
positions. The default switch settings in Ersky9x are associated with individual models and thus may
vary from one to another. They are checked every time you change models, not just when the
transmitter is turned on. This is an important safety feature but can be turned off if desired. The
throttle position is also checked when the active model is changed.
If a blank memory slot is made the active model, a basic fixed wing model based on the simple fourchannel template (see page 42) is created by defining standard mixes for channels 1 through 4. The
new model is initially named MODEL XX, where XX is the slot number.
Other Commands
Note that the commands in the Model Select menu (SELECT, COPY, etc.) apply to the model whose
number you have highlighted (which may not be the active model).
To COPY a model, highlight it and press MENU. Choose COPY and press MENU again to confirm
that you want to proceed with the duplication. The copy will be created in the first available blank
To MOVE a model, highlight it and press MENU. Choose MOVE, press MENU again. Use the
UP/DOWN keys to move it to a different memory slot and press MENU to drop the model there.
Moving a model will not overwrite other models.
To DELETE a model, highlight it and press MENU. Choose DELETE and press MENU. You will be
asked to confirm. Deleting a model moves up the models below it in the list. Note that you cannot
delete the active model; you first need to make another model the active one.
To BACKUP a model to the Micro-SD card, highlight it, press MENU and choose BACKUP. Press
MENU to complete the action. You will see “MESSAGE: MODEL SAVED” on the transmitter screen.
To RESTORE a model from a backup file, highlight a blank memory slot, press MENU and choose
RESTORE. Highlight the model you want to restore and press MENU. You will see “MESSAGE:
MODEL RESTORED” on the transmitter screen. Note that you can`t use Restore to replace an
existing model without first deleting that model.
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Backup files are saved on the SD card with a “.eepm” extension in a folder called MODELS. They
can be copied to the computer via USB or by using the SD card for the transfer (see Communicating
with a Computer).
In addition, .eepm files (which contain a single model) can be imported from the SD card into the
Eepskye program. There they can be edited and saved to the SD card, the computer or the
transmitter’s EEPROM file. See the manual Using Eepskye.
Setup XX (page 1/13)
The Setup screen has many lines and presents a wide range of settings specific to the individual
model that is currently active (Model Number XX). Select items in the menu using the UP and
DOWN keys. Here are the first items:
Name (model name)
This item works like Owner Name in the Radio Setup page. Choose a space where a letter is
required and press MENU to highlight it. When the UP or DOWN key is pressed the following are
shown in sequence: a blank space, upper case letters, lower case letters, numerals, '_' and '- 'and
'.'. When you have the correct letter or numeral in place, press MENU or EXIT to regain the ability
to move left and right. Use DOWN to get to the next item.
Voice Index
Here you specify the voice file that will be announced when the model is selected. Highlighting
the number and pressing MENU will cause the voice file to be played. The range of numbers is
260 to 309 –.if you don’t want a name to be announced, just assign a number that doesn’t have a
voice file associated with it (probably a high number). For more on this see ErSky9x Voice
Timer 1, Timer 2
There are two fully programmable timers, that can count either up or down. By default, the timers
are set to OFF and are not operational.
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Trigger A, Trigger B
Two triggers are available to start and stop each timer. Options for Trigger A (referred to as
simply Trigger in the screen) are OFF, ABS, THs, TH%, or c1% to c24%.
ABS counts up all the time, THs runs whenever the throttle stick is not at idle, TH% counts up at a
speed proportional to the throttle stick position, i.e., at 50 % throttle the timer runs at 50% of full
speed. The option of c1% through to c24% means the proportional output of any channel from 1
to 24.
Trigger B options are any physical switch or any virtual switch (more on those later). Both A and B
switches can control either count up or count down.
You can also enable voice announcements of time. 'Minute call' will say the time every full minute,
while 'Beep countdown' will give announcements several more times during the last minute. These
can be activated on page 1/11 of the Radio Setup menu.
T-Trim (Throttle Trim)
This is a useful feature for fuel-powered models. When activated (1) the centre detent for the throttle
trim is removed and (2) throttle trim affects only the “low” side of the throttle range. That means you
can use the trim for setting idle while full throttle remains unchanged. When not activated, throttle
trim has no effect.
6. T-Expo
Another throttle-related function, this one makes the throttle stick expo setting go from zero to full
instead of having a centre point like expo on all the others.
Trim Inc (Trim increments)
This setting determines how the active trims behave.
1. Exp – Exponential – trims are fine near the centre and get coarser further out.
2. ExFine – Extra fine – 1 trim step per click.
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3. Fine – 2 steps per click.
4. Medium – 4 steps per click.
5. Coarse – 8 steps per click.
Adjusting the trims produces a series of tones that rise in pitch as trim increases in either
direction. The center point of the trim range is signaled by a haptic buzz.
Trim Switch (“InstaTrim”)
When this switch is activated, the current position of the sticks is copied to the subtrim settings
(Limits page). Choose a switch that is easily reached but unlikely to be flipped accidentally (e.g.,
RUD). The function is triggered by moving the switch from its default position. To trigger it again,
the switch must first be moved back to its default position.
This function is very useful for first flights, as it avoids the need to take your hands off the stick to
press the trim buttons. Simply hold the plane level with the sticks and flick the selected Trim
Switch. Immediately centre the sticks and the plane is trimmed. Fine trimming can still be done
with the trim buttons.
NOTE: It is advisable to disable this function once initial trimming is completed as it can have
seriously negative results if triggered accidentally!
E. Limits
Extended limits. Allows control limits to go to plus or minus 125% instead of the normal 100%
maximum. Please test to make sure this does not cause unwanted mixing between channels or
exceed servo mechanical limits. Note that 100% on the Ersky9x firmware already corresponds to
125% on most other transmitters, so extended limits should not normally be required.
Trainer ON or OFF. This allows you to select whether for this particular model the trainer inputs
are available from a connected student transmitter. This is for use when the transmitter is serving
as Master in a buddy box arrangement. See page 14 for an explanation of the Trainer function.
Selecting OFF frees up a switch, usually TRN, for other purposes.
Auto Limits
This setting allows Subtrim to override the Limits setting so that servo throw remains the same on
both sides of center. The value here determines the maximum amount the limits can be exceeded
(e.g., a setting of 10.0 allows a limit set at 100% to go as high as 110%). Be careful when using
this feature as the control limit values are no longer absolute and could allow a servo to exceed a
mechanical limit.
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Switch Warning
If ON will show a warning when the switches are not at their default positions when the
transmitter is turned on with this model selected or when the selected model is changed to this
one. The transmitter will not output a signal until the alert is cleared.
Default Switch
Sets the default switch positions at start-up. Set the switches in the desired positions, then press
the Menu key. The switches in the ‘on’ position (up/back) will show as black on white, while those
that are ‘off’ (down/forward) will show as white on black.
Volume Control
This can be set to use one of the three potentiometers (P1, P2, P3) or a Global Variable (GV4 to
GV7). The volume control only works after you exit the menus.
Beep Cnt (Beep Centre)
Here you can set inputs to beep when centered. RETA123 corresponds to: RUD, ELE, THR, AIL,
P1, P2, P3 inputs. This is useful for locating the centre of the pots without looking (e.g., while
flying!). Press MENU to turn on centre beeping for an input.
Proto (encoding protocol)
PPM is the protocol used for many plug-in RF modules (including the OrangeRX DSM2/DSMX
and the FrSky DJT). You can set the number of channels to encode and the pulse spacing, but in
most cases, the settings should not be changed. (If you use a Spektrum DM9 module, set
spacing to 350uSec for more accurate centering.)
The PXX setting can be selected for the newer FrSky X8R module.
The DSM2 setting is used where an internal module extracted from a Spektrum transmitter is
"hacked" into the 9XR Pro. Instructions for doing this can be found at:
The DSM2 setting may also be used with future DSM telemetry modules.
Note: Each of the Proto settings opens up a different set of options. The following applies only to the
PPM setting. For PXX and DSM2 see documentation for that application.
Start Channel
This is the channel which is first in the PPM stream and is usually left at 1. Other start numbers
may be needed when using a flight controller which accepts the raw PPM.
PPM FrLen (Frame length):
The length of each frame within the PPM train. Normally need not be changed.
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Shift Sel (Shift select)
POS/NEG. Select signal shift. POSitive or NEGative. Leave at POS if in doubt.
PPM2 Start Channel
Where two receivers are used for extra channels, PPM 1 is set to match the capability of the first
receiver, while PPM 2 is set for the second receiver. If first receiver is an 8-channel unit, then the
second receiver will normally start at channel 9. The options are: ‘Follow’ or a specific channel
from 1 through 17.
PPM2 Channels
The options are 4 through to 16 channels in 2-channel increments. This depends on the number
of channels your second receiver or flight controller can handle and how many channels you
need to send.
Heli Setup (page 2/13)
A short press of the RIGHT key will bring up the helicopter CCPM head mixer screen. This page
allows setting swash plate type, and limiting the control authority through the Swash Ring setting.
Note that many modern rotary wing models, whether flybarless helicopters or multirotor machines,
use an on-board flight controller that cannot accept CCPM mixing. Likewise, coaxial helicopters
typically require only simple fixed wing type inputs for the rotors (aileron, elevator, rudder) and
throttle to control climb and descent. For such models, you can ignore this page.
The inputs to the CCPM mixer are the AIL and ELE sticks, plus the input or virtual channel selected
in "Collective" (which has entries on the MIXER page for one or more pitch curves). Here are the
This defines the type of swash plate used by the heli:
120: “Standard” 120 degree swash plate. The “pitch” servo is towards the front/back.
120X: Same 120 degree swash plate but turned 90° so the pitch servo is on one side.
140: Less common 140 degree swash plate – the “pitch” servo is towards the front/back.
90: Basically a simple 90 degree setup where a single servo operates the collective pitch directly
and aileron and elevator servos tilt the swash. May be used for fixed pitch helis.
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This defines the source of the collective input. The idea is that you can create a mix in a virtual
channel (above those sent to the receiver) incorporating all the required curves and switches,
then simply use it as the input here to mix with the other inputs.
Swash Ring
As the name implies, this feature limits stick movement just like a physical swash ring. Notice that
this feature only works on AIL and ELE, regardless of radio mode selected.
ELE/AIL/COL Direction
These allow the direction of the input functions to be inverted. Use them to make the controls
move the correct way when setting up your heli.
The outputs of the CCPM mixer are CYC1, CYC2 and CYC3. These need to be assigned on the
MIXER page to the channels that will drive the swash servos. The settings made here have no effect
unless you use the CYC1, CYC2 and CYC3 outputs.
As noted above, a multirotor or flybarless helicopter which uses onboard computers/mixers will NOT
use the CCPM mixer or these outputs.
For more information on setup please consult forums devoted to the relevant type of helicopter.
Modes (Flight Modes) (Page 3/13)
A short press of the RIGHT key will bring up the flight modes screen.
Seven flight modes are available: the default mode FM0, plus FM1 to FM06. Each can be named
and has a selectable activation switch (physical or logical), a trim selection array, and slow up/down
parameters for smooth transitions between modes.
One main reason for using Flight Modes, rather than just programming the required features directly,
is to allow separate trims for different modes. When shown, R, E, T and/or A mean that a mode has
its own trim setting for that control (see below); each can be changed to a number corresponding to
another FM and thus use the same trim values as that mode.
The other main use of FM is to determine which mixes are turned on for each mode.
The priority of the flight modes is such that the first FM that has its switch ON is the active one.
When none has its switch ON, the default FM0 is active.
Expo/DR (page 4/13)
This is the first step of the control chain –defining the response curve of each stick and the amount
of control authority it has. This page is where you define how the transmitter sticks provide inputs to
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control your craft (the next page, Mixer, is where you define how those inputs are combined and
transformed). If it's something the about the stick inputs you need to do, then this page is where you
do it.
The Expo feature allows you to make the stick input non-linear. Instead of a straight line that
represents equal response at any point in stick travel, expo causes a given amount of stick
movement around centre to produce a smaller servo movement than the same movement near the
extremes of stick travel. The line becomes a gentle S-curve and the model can be flown more
smoothly. This is called normal expo and for transmitters using open source firmware, it is
designated by a positive number (Spektrum and JR follow this convention, but Futaba and Hitec use
negative numbers for the same result – yes, it’s confusing!)
Dual rate (DR or D/R) allows you to select the sensitivity of the control setup in terms of servo travel
for a given stick movement. Reducing the rate tilts the whole control curve, from the default 45°
(50% stick movement produces 50% servo travel) to a lower slope for more gentle and precise
control. On the 9XR Pro either dual or triple rates can be used.
On the second line of Expo/DR screen you can select to which stick (RUD, ELE, THR, or AIL) the
settings below apply. The graph changes as you enter values so you can see if you are adjusting the
line in the correct way and get a sense of proportion. Here rudder is selected.
For each control you can input values for both expo and D/R by highlighting the field and using the
navigation buttons to change the value. For example, to edit an expo value, press the DOWN key
until the cursor blinks on the expo value. Then use the LEFT/RIGHT keys to change the value. If the
stick is in its centre position, both expo values will blink and any entry will adjust the expo equally
both sides of centre. However, if, for example, you hold the stick left of centre, only the left value of
expo will blink, and the keys will change only the left side of the graph and left side of stick travel. In
this way you can have a different expo curve on one side compared to the other.
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For each control you can set two switches. For a dual rate arrangement, simply chose the
appropriate switch (say ELE) for DrSw1 and leave DrSw2 blank. To have the switch work in the
reverse direction, choose the “not” form (!ELE).
For a triple rate arrangement you can us two switches. The main switch changes between high and
mid-rate. If the main switch is “low” (i.e., mid-rate) the second switch can then switch between mid
and low rate.
The three position switch (ID0, ID1, ID2) switch can also be used for triple rates. For DrSw1 enter
“!ID2” (remember the exclamation mark means “not”) and for the DrSw2 enter “!ID1”. The logic is
that Sw1 is not ID2 so it must be either ID0 or ID1. Likewise if Sw2 is not ID1 it must be ID2.
Mixer (page 5/13)
This is where you manage the relationship between the inputs (sticks, pots and switches) and
outputs (servos, speed control). In Ersky9x the only predetermined mixes are the basic four channel
setup that is automatically created for every new model, plus templates for some additional mixes,
notably V-tail and Elevon/Delta. All of these can be edited and beyond them you have the freedom to
define exactly what you want the servos to do.
Here’s what a simple mixer page might look like. This one has two channels for aileron (CH1 and
CH2) to allow the two servos to be controlled separately. Both get their input from the aileron stick.
The various channels numbered on the left of the screen are outputs from the mixer to the servo. For
example CH1 is servo slot number 1 on your receiver. CH2 is servo slot number 2, and so on.
What this screen is telling you is, for example, that the rudder stick input is being routed by the
mixer, with a 'weight' of 100%, to the servo plugged into CH4 on the receiver. Similarly for the
elevator, throttle and aileron channels.
In this case, the switch column is empty, meaning that the mixes are turned on all the time (the usual
situation for the stick inputs in a simple model). The curve column shows that c1 and c2 are being
applied to CH1 and CH2, the two aileron channels in this setup. They are providing aileron
differential (meaning that the ‘up’ aileron moves more than the ‘down’ aileron.
A channel without a mixer command line (such as CH6 here) will simply centre any servo connected
to it. The servo will not move at all as it has no variable input.
Edit Mix
Let’s assume you have highlighted a channel in the screen shown above and given a long press of
the MENU key. You see this screen:
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Then you select Edit and get this:
Editing the Mix
We need to take a pause here and look closely at the choices available to us in setting up a mix.
Here is where you can determine how the source (input) will be transformed into output that drives
the servo(s) plugged into that receiver channel.
It’s important to understand that in the Ersky9x kind of programming, the only way anything can be
controlled is through an explicit mix. In many other radios, most of the mixes are built-in but hidden;
here they are fully visible and editable, giving the radio enormous flexibility and power, but requiring
that you create the mixes.
Here are the available options for each mix :
1. Source: This is the input for the mix. It can be any of the following:
Stick or potentiometer (RUD, ELE, THR, AIL, P1, P2, P3).
HALF: Output is either 0 or Weight. It is controlled by the designated switch (see 6).
FULL: Output is either -Weight if the switch is OFF or +Weight if the switch is ON.
3POS: The Three Position Switch ID0, ID1, ID2. Has three values: weight, 0, -weight.
Centre position is 0 unless an offset has been defined.
CYC1, CYC2, CYC3: The three outputs of the heli swash-plate mix. Once swash mixing is
turned on (Heli Setup, page 3/10) these mix inputs become active and reflect the result
of the swash mix.
PPM1..PPM8: These are fed by the PPM input or “trainer port”. They can be used to
configure a buddy system or to simply extend the radio with more functions (like head
tracking for you FPV guys). Note that the Trainer page under Radio Setup deals only
with CH1 – 4. PPM input offers a more flexible means to share control of up to eight
channels with a slave transmitter.
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CH1..CH24: Outputs of the mixes on virtual channels (channels not sent to the receiver).
This capability can be used to chain mixes for more complex behavior.
GV1..GV7: The values of the Global Variables
THIS: A source that represents the combination of all mixes for the channel to this point.
2. Weight: This value multiplies the value from the input. It can range from -125% to +125%.
Default is 100%.
3. Offset: This value is added to the value from the input. It can range from -125% to 125%.
Default is 0%.
4. Trim: When this is ON, the trim value (if it exists) will be carried through the mix. When OFF
any trim value is ignored.
5. Curve: This applies a function or curve to modify the application of the source value.
x>0: The value of the source is carried through only if it is positive (greater than zero). If the
source value is less than zero, a zero value is applied.
x<0: Same but for negative values.
|x|: The value is passed as an absolute value (-50 and +50 are both treated as 50).
f>0: If the source is positive then the output value is “+weight” otherwise it is 0.
f<0: If source is negative then the output value is “-weight” otherwise it is 0.
|f|: Output is either “+weight” or “-weight” depending on the sign of the source.
c1..c16: Custom Curves. These are defined in the “CURVES (6/8)” screen. You can press
MENU to edit the curve directly. When you are finished making the curve, short press
the EXIT key to return to the EDIT MIX menu. See the Glossary of Terms for an
explanation of the mathematical relationships used above.
Pressing MENU when 'curve' is highlighted changes this function to allow the source value to be
modified by a differential value. Using the DOWN key highlights the value under the word 'diff''.
The LEFT and RIGHT keys adjust the value. The range of possible values is 0 to +/- 100. This
value is the percentage reduction in servo travel one side or the other of centre.
6. Switch: Here you select the switch that controls the mix. If a switch is not selected then the
mix is ON by default.
7. Warning: Here you can select an audible warning that will sound whenever a mix is turned
on (only works when a switch is defined). You have an option of 1, 2 or 3 beeps. The
warnings will sound in succession so you can hear them individually.
8. Multpx (multiplex): This value defines how the mix will affect the channel.
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Add: This is the default value. With this value the mix is added to the previous values in the
same channel.
Multiply: Use this to multiply the previous values in the same channel.
Replace: This value is used in conjunction with a switch. When the switch is off the value is
ignored. When the switch is on the value discards the previous values and places its
own value in the channel.
9. Delay Down/Up: Use this to delay application of the mix. Usually used with a switch. When
the switch is turned ON or OFF the mixer will wait the specified number of seconds before
changing the value.
10. Slow Down/Up: Slow the rate of change in the channel. When not zero these will determine
the maximum speed with which the value can change. The specified value is the number of
seconds to go between –100% and 100%.
Example of a Mix
An electric powered glider usually flies a lot faster when climbing than when gliding. The extra speed
generates more lift from the wings, so the model wants to do a large loop. A little down elevator is
required to keep the nose from lifting. We need a mix to do this automatically.
Assume the throttle is operated by a switch and therefore full power is applied instantly. The Gear
switch (GEA) is being used to control the motor and is on CH5, as shown below:
When the GEA switch is flipped to ON, the signal to the ESC via CH 5 goes from -100% to +100%
because that’s how the FULL input works: the value is either –weight or +weight.
In order to have this power-up command affect not only the motor via the ESC but also the elevator
servo, we need the GEA switch to control a mix in the Elevator servo channel (CH3). But we only
want a small effect, say 5% weight.
To create this mix navigate down the MIXER page to highlight the Elevator channel and press
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In the resulting pop-up menu select INSERT. This creates a new mix line.
Press MENU. This takes you into the edit menu for the new line.
In this menu, the first field asks for the source of the mix. Because we are using a switch and not a
stick we want the source to be FULL or HALF. A switch has no intrinsic value unless a source is
assigned to it. Two possibilities are available for our purpose:
FULL operates from --100 to + 100.
HALF operates from 0 to +100.
For the elevator we choose HALF because we only want zero or negative movement (down).
The next field is the weight. If we entered 100 the elevator output would move from 0 with the switch
OFF to + 100 with it ON. This is clearly too much movement. As we need only a fine adjustment let's
try a weight of 5%. After the test flight this can be increased or decreased.
On the ground with motor disconnected, check that the elevator compensates in the correct direction
(down). If not, invert the weight to minus 5. (i.e., just highlight the number and press both the RIGHT
and LEFT keys simultaneously).
Leave offset at the default zero. We don’t want to shift the point where the mix operates.
Next to edit is the switch field, where we select GEA to serve as the throttle switch.
The 'multpx' field determines how mixes interact. By default it is set to 'add', which in our case is
what we want to do, i.e., add this small elevator servo movement to whatever inputs come from the
elevator stick.
Those are the standard mix elements. Now for something a little more sophisticated.
Consider the behavior of the model when you apply throttle. Even with the motor switched to full
throttle, the model will take time to accelerate and make the wings generate much extra lift. So we
need to delay the application of lift compensation (down elevator), let’s say by one second. So we
enter 1 into the 'delay up' field. 'Up' refers to the increasing input to the motor, not to elevator
movement. But the model will not achieve full speed until sometime later, say 3.5 seconds. To apply
the elevator correction gradually, therefore, we enter 3.5 in the 'slow up' field. The result is that when
the throttle switch is activated, the motor starts immediately, but the down elevator lift compensation
does not start for 1 second, and then takes 3.5 seconds for full deployment.
Now consider what happens at the top of the climb. The throttle switch instantly cuts the power. The
model will be going fast so down elevator is still required to prevent the model from pitching
upwards. We need to delay the return of the elevator to zero by let’s say 2 seconds to allow the
model to slow down. Enter 2.0 in the ‘delay down’ field. To avoid an abrupt change in the aircraft’s
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attitude we can also slow the elevator movement so it takes say 1 second to return to neutral for the
glide. Insert 1.0 in the 'slow down' field.
Here’s what the mix screen looks like with these changes:
We now have a mix line in the elevator channel, using the throttle switch as the source, which gives
5% down to compensate for the extra lift generated under power. We have a 1 second delay before
the elevator compensation starts and a 3.5 second period for it to reach full deployment. At throttle
off, we have a delay of 2 seconds while the model slows and then a 1 second period during which
the elevator resumes the neutral position for the glide.
Now we test the model by flying it to see if the settings are correct and change them as necessary to
give a straight climb trajectory and smooth transition to the glide.
Limits (page 6/13)
Limits operate on the output channels. In the LIMITS menu you can set the centre point (subtrim),
set the limits (both left and right) and reverse the output of the channel (INV for invert). Use the
MENU key to activate a field and then use the RIGHT or LEFT keys to increase or decrease the
value. Use EXIT to finish editing.
Each channel here corresponds to a channel in the receiver. The limits you set on a line apply to that
channel only. Here’s what you see in this screen:
subT: Subtrim (first column)
This sets the channel's centre point.
The values of subT can be -100 to 100. Increments are 0.1, giving fine resolution when
setting the centre for each channel.
You can also use the stick to set the centre point. While subT is highlighted hold the
stick so the surface is centred. Long press MENU and the position will be recorded.
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Min/Max: Limits (second and third columns)
These set the endpoints of the channel. An arrow indicates which side is active; it
changes as you move the stick or other input.
Each limit can range between -100% and +100%. The settings not only impose absolute
limits on servo throw but adjust the gain and thereby maintain proportional control
throughout the servo movement.
INV: Invert. (fourth column)
This reverses the output of the channel. Choices are ‘---‘ or ‘INV’.
At the very bottom of the LIMITS screen is the option: COPY TRIM [MENU].
When you have landed after trimming your model to fly straight and level by using the trim
buttons, you can select this command line and press the MENU button. The radio will beep, the
trims will be converted into subtrim values, and the trim positions shown on the ‘Home’ pages will
all be returned to centre.
Note that InstaTrim (controlled by the switch selected as ‘Trim Switch’) offers another approach to
trimming by converting stick positions to subtrim in flight (see page 21). The two methods are
Curves (page 7/13)
Curves tell your servo how to move in response to your stick movement. In ErSky9x there are eight
5-point curves and eight 9-point curves.
A 5pt curve is a curve you can edit at positions: -100%, -50%, 0%, 50%, 100%.
A 9pt curve is a curve you can edit at positions: -100%, -75%, -50%, -25%, 0%, 25%,
50%, 75%, 100%.
Curves CV1 to CV8 are 5-point, while CV 9-16 are 9-point. Here is an example of a 5-point curve:
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Scroll down to the curve you wish to modify and press MENU or RIGHT. This will bring up the
screen for editing the curve:
You will see 5 or 9 editable points with the values initially set a zero. Scroll through the points with
UP/DOWN. Change the value with LEFT/RIGHT.
If you select the “PRESET” entry, pressing LEFT or RIGHT will populate the values with a linear
curve (i.e., straight line) that is a good starting point. LEFT gives lines sloping up from left to right.
RIGHT gives lines sloping the other way. Pressing the key repeatedly changes the slope. The
individual points can be edited by highlighting, pressing MENU and then using the RIGHT/LEFT
keys to adjust the value. Press EXIT to navigate to the next point.
The graph will show the shape of the curve as you edit the points.
Custom Switches (page 8/13)
These are logic switches that are used to compare values and combine various conditions. More
precisely, they are a set of logical functions that can be used as switches. There are 24 such custom
switches in ErSky9x.
The first column shows the "operation", listing several arithmetic, logical and differential operations.
In arithmetical operations, v1 and v2 represent variables, v represents a value, and ofs represents
an offset (i.e., a constant).
Variables can be any source, i.e., all those available in mixers, plus the seven global variables and
all telemetry values. In logical operations the available sources are all the physical switches and the
other custom switches. Differential functions compare the changes in a variable since it was last
matched to another value.
Once the defined condition is met, the value of the switch will be “ON”.
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Setting Up a Custom Switch
First we define the condition or operation. This can be: an arithmetic function, or a logical condition,
or an evaluation between two sources.
1. If you've selected a regular condition (v>offset, v<offset, |v|>offset or |v|<offset), you need to
specify a source for the value and an offset:
The source can be a stick, pot, PPM input, output channel or telemetry value.
The offset can be anywhere between -100 and +100. It will be the test point for the
For example: switch “ON” only if throttle is above 50% (THR > 50)
2. If you've selected a logical condition (AND, OR, XOR, Latch, F-Flop), the conditions of the two
selected switches are evaluated.
For example: switch “ON” if either ID1 or ID2 is ON (OR ID1 ID2).
3. If you've selected an evaluation (“==”, “>”, “<”, etc...), you need to select the two sources to be
For example: Switch “ON” only if CH1 is less than RUD (V1<V2 CH1 RUD)
AND Function
Custom switches also offer an extra AND condition. If this is selected in the first column, it must be
ON for the custom switch to become active.
For example to turn on the timer with the THR switch and have the time announced every 30
The last field (THR) is the AND condition. The timer only runs when the THR switch is ON.
To finish the job, a voice switch needs to be set. More on that in the next section.
Latch and Flip-Flop Functions
Two special functions available in custom switches are helpful when it is necessary to use a brief
input to trigger a persistent state.
The Latch function allows a state or event to be captured and held for as long as required. For
example, the maximum altitude reached by a glider can be retained until it is desired to measure a
new maximum.
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Two switches are used as input to the Latch function. Turning ON the first sets the custom switch
output to ON. When the first switch is ON, the second switch has no effect, but when the first is OFF,
turning OFF the second will reset the custom switch to OFF.
For example, the following causes SW3 to turn ON when the TRN switch is pulled and off if the RUD
switch is turned ON (but only if the TRN switch is released to OFF).
Latch TRN
The Flip-Flop (F-Flop) function “remembers” the input state and provides it as the output. Again,
two switches are used for input, one as the trigger and the other to provide the “data”.
So, for example, if the momentary TRN switch is used as the trigger, pulling it ON sets the output of
the custom switch to the current state of the second input.
For example, the following entry causes the value of custom switch 4 to change every time the
trainer switch is pulled, as the second input is defined as opposite to the current state.
F-Flop TRN
Safety Switches [and Voice Switches] (page 9/13)
This page allows you to define safety switches that will overwrite the existing value for a particular
channel. It also includes provision for audio warning switches and voice switches to announce
Safety Switches
There are four types of safety switch:
S (Safety): Replaces the existing value for the channel when a switch is on.
X (Sticky Safety): Overwrites the existing value for a particular channel.
A (Audio): Plays a sound or haptic vibration chosen from a list.
V (Voice): Plays a voice file.
To use the basic S-type safety switch, suppose you want to set a simple safety switch to lock the
Electronic Speed Control (ESC) of an electric model at zero throttle. If Channel 1 is throttle, and full
low throttle is -100, then what you need is:
This means that when the THR switch is ON the safety switch ensures that value of Channel 1 is
always -100, regardless of the position of the throttle control. When the THR switch is 'OFF' the
channel works normally (typically controlled by the throttle stick). In the screen below, the first
column is the channel to which the safety switch applies, ‘S’ identifies this as a safety switch and
THR identifies the physical switch.
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Warning! When a safety switch is active, the output of the channel is replaced by the defined safety
switch value (here -100). The value of the channel, however, continues to be determined by the
throttle stick position (and any other mixes that feed into it). If you were to have a mix to feed in
down elevator in proportion to the throttle setting, cutting off the motor at full throttle with the safety
switch would leave the elevator still in its down position.
The X-type safety switch works exactly like the basic safety switch, except that it is “sticky”. Before
the channel can function normally again, the throttle stick must be returned to full low (-100). In other
words, the X-type safety switch performs the same function as the Sticky T-Cut template (though the
latter works in a different way).
The A-type safety switch (for Audio) at 4 second intervals plays a sound or haptic vibration chosen
from the following list: Warn1, Warn2, Cheep, Ring, SciFi, Robot, Chirp, Tada, Siren, AlmClk,
Ratata, Tick, Haptc1, Haptc2, Haptc3. Here’s an example:
This will cause a double ring sound every four seconds whenever the Aileron switch is ON.
The V-type safety switch will play a voice file every 4 seconds when the switch is ON.
For example:
This will say “Flaps second position” when the 3-position switch is full down. For full control of voice
announcements, use a Voice Switch, as explained below.
Voice Switches
Following the 24 Safety Switches (CH1 to 24) are, by default, 8 Voice Switches (VS 25 to 32) that
trigger the playing of a particular voice file and determine the conditions and manner in which it is
played. If more than eight Voice Switches are required, Safety Switches can be converted into Voice
Switches. At the top of the screen the value of ‘Number Voice Sw’ can be adjusted to increase the
default 8 up to a maximum of all 32 switches.
The following picture shows the lower portion of the list, where Safety Switches give way to Voice
If the number of voice Switches were increased to, for example, 10, then CH23 and CH24 would
become VS23 and VS24.
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In this screen, the first column identifies the Voice Switch number.
The second column may contain any physical or virtual switch such as RUD, ELE, ID0, ID1.....SW1,
SW2, SW3,...etc.
The third column may contain ON,OFF, BOTH, 15 sec, 30 sec, 60 sec, and Varibl.
ON means that when the switch is activated, the item in the fourth column will be announced.
‘BOTH’ is a means of activating both ON and OFF voice switches from the one command line
provided the two voice files are consecutively numbered and are consecutively ON and OFF files.
For example, the command:
means that when the GEA switch is activated the transmitter plays file 76 ‘Gear Up’ and when the
switch is deactivated it plays file 77 ‘Gear Down’.
The fourth column may contain a voice file number, a telemetry value, Timer 1 or Timer 2 value, or
the value of a Global Variable (see page 43).
Telemetry (page 10/13)
It is beyond the scope of this manual to provide a detailed explanation of the details of using any
particular telemetry system, but the following provides an introduction to the basic FrSky approach
using analog inputs. For more detail on this and the digital approach being used increasingly, go to:
Ersky9x also supports the Winged Shadow How Hi unit and will accept input from DSM telemetry
when available.
The first item on the page is ‘UsrProto’, where you select between WSHhi (Winged Shadow How Hi),
FrHub (FrSky Telemetry Hub) and DSMx (DSM2 or DSMX Telemetry). On the same line you can
select either Metric or Imperial units.
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A1 and A2 on this screen refer to the two analog inputs available on FrSky D-series receivers. These
inputs can accept a maximum of 3.3v. To measure higher voltages, therefore, a voltage divider
consisting of a pair of resistors must be used. For example, a divider with 4:1 ratio will measure
voltages up to 13.2v (4 x 3.3v).
The A1 input is normally used to measure receiver voltage. All of the FrSky D-series and X-series
receivers do this by connecting the A1 input by way of a built-in 4:1 divider.
The A2 port does not provide an internal voltage divider. Consequently, to measure voltages above
3.3v, an external divider must be used as a voltage sensor. For example, to measure the voltage of
a 4-cell LiPo battery (maximum 16.8v fully charged), a 6:1 divider can be used; this will accept
voltages up to 6 x 3.3v = 19.8v. With such a divider, 16.8v will be seen as 16.8v/6 = 2.8v as input to
the receiver telemetry.
Note that the FrSky X8R receivers only have only one analog input, A1, which is connected
internally to measure the voltage of the receiver power supply. A converter is available to enable
analog inputs (A2) to the digital S.Port of the X8R. The X6R receivers have an external A1 port like
that on most D-series receivers.
Within the telemetry circuits of the receiver, the value of the analog input (between 0 and 3.3v) is
converted to a number between 0 and 255. This is encoded digitally and sent to the transmitter,
where it is converted back to a number representing the voltage (to do this the transmitter must be
given the divider ratio).
In the screen shot above, the numbers immediately to the right of “A1 channel” and “A2 channel”
represent the measurement Range, which depends on the divider ratio of the voltage sensor. For
the 4:1 ratio used to measure receiver voltage, this value should be set to 13.2 (i.e., 3.3 x 4). For a
6:1 ratio sensor, the range would be 19.8.
The number in the right hand column (5.2 in the picture) represents the final Telemetry read-out. If it
does not agree exactly with the actual value measured with a voltmeter, the range value can be
adjusted slightly. The usual cause of inaccuracies in the reading is the tolerance of the resistors
used in the voltage divider.
The lowercase ‘v’ following the Range value represents one of four scaling factors used in
converting the telemetry number (0-255) into a suitable read-out value. The ‘v’ setting corresponds
to a read-out range of 0 to 25.5 volts, while a ‘V’ setting gives 0 to 51 volts (at reduced resolution).
Set to ‘A’ for current measurement, the telemetry number is converted to a range of 0 to 65 Amps.
Finally, the ‘-‘ setting displays the unconverted telemetry number (0-255), which can be used for
parameters other than voltage or current, such as temperature or RPM, depending on the sensor.
The A2 read-out works in the same fashion. The Range setting will depend on the sensor being
used. For the FBVS-01 voltage sensor, using the default ratio of 1:6, the range setting would be
19.8v. Fuel level, GPS position, Altitude, Current and RPM may also be measured using FrSky
sensors which plug into a hub. The hub produces a stream of signal outputs suitable for the serial
port on some D-series receivers.
When using third party sensors, the scaling factor of the voltage divider depends on the type of
sensor installed and the magnitude of the values being measured. Refer to the instructions which
come with the sensor for details on how to install and calibrate it.
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"Low" and "Critical" alarms for A1 and A2 will trigger audio warnings (beeps) when the measured
value goes below the defined levels. These are defined as Yellow, Orange and Red. to differentiate
among the various beep patterns. Voice warnings can be enabled for A1 and A2 values if a custom
switch is used to detect the alarm condition and a voice switch is used to play an appropriate track.
Similarly audio alarms will be triggered at “warning” and “critical” levels if the received signal strength
indication (RSSI) or the receiver voltage falls below the set levels. These settings, at the bottom of
the Telemetry page, are shown above.
Telemetry 2 (page 11/13)
This page continues the telemetry settings:
RSSI Alarms: TxRSSIalrm and RxRSSIalrm refer to the levels at which warning beeps are produced
directly by the FrSky module (see page 10). The numbers here are read from the transmitter
module. If you have modified a FrSky DJT module in accordance with the instructions in the manual
Introduction to the Hardware, these numbers may not appear. They are normally set to zero (turned
off), as shown above, to avoid conflict with the RSSI alarms set on the Telemetry page,.
mAh Alarm: This warns when a set amount of battery capacity has been used. A current sensor
must be used to provide the necessary input. The sound or haptic buzz used for the warning can be
selected from the list provided.
Num Blades: Number of blades for the RPM sensor.
AltAlarm is the altitude alarm. Altitude is measured by a barometric device in the Winged Shadow
How Hi unit. A frequently used setting is 122 metres (which will display as 400 feet if ‘Imperial’ is
selected on the previous telemetry page).
Voltage Thresh (Threshold): Allows the alarm threshold to be chosen.
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GpsAltMain is the Global Positioning System (GPS) determination of altitude and may be turned ON
or OFF. If ON, the barometric altitude reading is replaced by GPS altitude.
Telemetry 2 Custom Display
Short presses of the DOWN key will take you to the custom telemetry display screen.
Up to six telemetry variables can be displayed on a single screen in the order you select. Highlight
the blank line and using the LEFT or RIGHT keys select from the options available. You must have
the corresponding telemetry sensors and hub installed in your model. BT (Bluetooth) . Telemetry
may be OFF or ON.
FrSky Port refers to the port used to connect the FrSky telemetry hub to the receiver. It may be
either port 1 or port 2
Each field in the custom display can be one of the various available parameters as follows:
Tmr1,2: Both timers in the transmitter
RSSI: Lowest of the RSSI values from the radio and receiver in D8 mode
A1, A2: Analog ports on D receivers Alt: Barometric altitude sensor
Rpm: Engine speed, number of blades is adjusted in the settings above
Fuel: Fuel level, mAh consumed
T1, T2: Temperature sensors 1 and 2
Spd, Dist, GAlt: GPS speed, distance from starting point and GPS altitude
Cell: Lowest cell on FLVS-01
Cels: Sum of all cells on FLVS-01
Vfas: FAS-40/100 voltage measurement
Curr: Current, source configured in the settings above (FAS or analog)
Cnsp: mAh consumed in total (needs current source configured correctly)
Powr: Power, voltage and current sources configured above
AccX, Y, Z: Acceleration values from TAS-01
Hdg: GPS heading
Vspd: Vertical speed (either calculated by the radio or reported by the sensor, depending
on the sensor type chosen above)
In the custom telemetry display, when pressing LONG MENU:
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If ALT is displayed, set to 0.
If A1 or A2 is displayed, and is measuring current, use the present value as an offset,
thus setting the displayed value to zero.
If a SCALER is displayed (see page 43) and its source is ALT, the ALT value is used as
an offset to set the ALT value displayed to zero.
The following is an example of a custom telemetry page:
Templates (page 12/13)
The templates are "starting points" for model setups. When selected with MENU LONG they will
either add to or replace the current model's mixes and settings with standard ones for a particular
usage scenario. They are best applied to a newly created model. They can be tweaked to achieve
the desired result, or simply used to get an idea of what's required for the particular model type.
At the bottom of the list (most quickly reached by pressing UP from the first item in the list) we
find the option to clear all mixes in the Mixer screen.
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01 Simple 4-CH
Creates a basic four channel fixed wing model with 100% weighting on each of the channels.
Channel order is determined by the setting in Radio Setup page 1/11. Note that applying this
template overwrites anything already set for channels 1 to 4.
02 T-Cut
Inserts a mix line for the throttle channel that replaces throttle stick input by -100% when the
THR.CUT switch is ON. When the switch is OFF, the throttle stick is immediately active.
03 Sticky T-Cut
Replaces throttle stick input by -100% when the THR.CUT switch is ON. When the switch is moved
to OFF, the throttle stick remains inactive until moved to the throttle closed position. (The “sticky”
mechanism is located on CH14, which is not sent to the receiver.)
04 V-Tail
Inserts mixes for both rudder and elevator input into the two channels used for the tail servos. When
the elevator stick is moved up, both surfaces move up. When the rudder stick is moved right, the left
surface goes up/right and the right surface goes down/right. Note that this mix may overwrite existing
05 Elevon/Delta
Similar to V-Tail but inserts mixes for aileron and elevator into the channels that control the elevon
servos. When the elevator stick is moved up, both surfaces move up. When the aileron stick is
moved right, the left surface goes down and the right surface goes up. Note that this mix may
overwrite existing mixes.
06 Heli Setup
Sets up basic CCPM mixes for a collective pitch flybar-type helicopter with the common 120° swash
arrangement. The three swash servo output channels are CYC1, CYC2, CYC3. Flight Modes are
controlled by the 3-position switch. Curves c1, c2, c3 are used for throttle on CH5, while c4, c5, c6
are used for pitch on CH 11 (in this case a “virtual” channel not sent to the receiver). Note that this
mix may overwrite existing mixes.
07 Gyro Setup
Creates adjustable outputs on CH6 controlled by potentiometer P2 and the Gear switch to set the
gyro gain for a helicopter.
08 Servo Test
Uses mixes on channel 16 to generate an output on channel 15 that slowly varies from -100 to +100
and back again. To apply this output to another channel, set up a mix with CH15 as the source.
09 Range Test
Generates a varying output on channel 24 that can be used to drive servos on other channels and
thus allow range testing with the transmitter in a fixed location and the model carried to a distance.
Maximum range is indicated by servos ceasing to cycle smoothly.
Note: The built-in templates cannot be edited or replaced. As a starting point for new models, you
may wish to create generic models and store them either on the computer (using Eepskye), or in
unused model memories of the transmitter, or on the SD card.. You can then simply copy, rename
and adapt a suitable model as required.
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Global Variables (page 13/13)
Global variables are values that can be substituted for the usual number on any Weight, Offset,
Differential or Expo setting. Their main use is to group the adjustment of several parameters that
should have the same value. For example, aileron differential on a glider with four surfaces
responding to the aileron function. When trying to find the sweet spot for the differential value,
instead of having to separately edit the differential value in the mixers, all four can be set to use a
global variable (i.e., GV1 can be selected by a LONG press of the MENU key on the Differential
field). Then adjusting GV1 on this page is all it takes for all four differentials to be updated
For example, to use a global variable in the EXPO/DR menu, highlight the Expo or D/R value and
then long press MENU key. You will then have the ability to select GV1 through to GV5. Then in the
GLOBAL VARS screen (above) define the GVx, which you chose to be any of the potentiometers,
P1, P2 or P3. Go back to the EXPO/DR screen. As you adjust the potentiometer, the value of the
Expo changes and the shape of the graph changes.
A scaler is a function that takes an input value and applies an offset and scaling (multiplication or
division by a fixed ratio). The result may be used for: display on the custom telemetry screen, voice
output, as the source for a mix, or as a comparison value for a custom switch.
For telemetry display purposes each scaler may be given a four character name. For both telemetry
display and voice usage, the units may be selected, together with the number of implicit decimal
places. The parameters for a scaler are:
Source: Stick/pot value, trainer input, channel output or telemetry value.
Offset: -125 to +125.
Multiplier: 1 to 256.
Divisor: 1 to 256.
Unit: Select from Feet, Volts, Deg_C, Deg_F, mAh, Amps, Metre, Watts.
Negate: Change the sign of the result
Precision: Number of decimal places 0, 1 or 2.
Offset At: Define whether the offset is applied First, or after the multiplier and divisor.
Name: four-character, user-edited name.
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Note that the output of a scaler can be used as an input (source) for the vario sensor telemetry value
or for a global variable (GVAR).
There’s a lot to learn about Ersky9x if you want to get the most out of your 9XR Pro. It may all look
quite intimidating, but most of it you don’t need initially (or perhaps ever) and can learn as you go
along. Programming a simple model is not very difficult and you can leave the more complex
capabilities of the firmware until you really need them. But do visit the documentation from time to
time to remind yourself of the amazing capabilities of this programming system. You will find
something new and useful every time.
Initially, people who have worked with other transmitters may find this one very different. But most
people find that once they “get” the Ersky9x approach, programming models is often quicker and
easier than with the approach used by traditional transmitters. And certainly when they get to more
complex models, the power and openness of the Ersky9x approach makes things easy that are hard
or impossible on many traditional transmitters.
We hope this manual will help you understand Ersky9x and that programming the firmware will
become a major part of your enjoyment of our hobby.
One last thought. Do explore Eepskye on your computer. Not only does this program offer an easy
way to create new models and fine tune existing ones, but it will help you update the firmware and
backup your models to the computer.
Note on Firmware Versions
This manual is based on version r204 of the Ersky9x firmware, issued in
May 2014 and installed in production models of the 9XR Pro with serial
number 3001 or higher. Radios with serial number 1-3000 come equipped
with version r202. The only significant difference is that r202 does not
include the Latch and Flip-Flop functions, documented in this manual on
page 34, or the default of eight voice switches in the Safety Switches menu
(see page 36).
To check your version number, see page 14 of this manual. Instructions for
flashing an update can be found in the manual Communicating with a
Computer. If you use the eepskye program on your computer, it can
automatically check for updates and download the latest file ready for
The latest firmware file can be obtained from:
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Further Information
For additional information to help you understand and make best use of your Turnigy 9XR Pro, see
the other manuals in this series and/or go to one of the forums dedicated to this transmitter and the
open source firmware it uses.
9XR Pro Manuals
The following manuals are designed to help you get the most out of your Turnigy 9XR Pro. They are
available at:
1. 9XR Pro: Introduction to the Hardware
2. 9XR Pro: First Steps with Ersky9x
3. 9XR Pro: Ersky9x Explained
4. 9XR Pro: Communicating with a Computer
5. 9XR Pro: Using Voice with Ersky9x
6. 9XR Pro: Using the Eepskye Program
7. 9XR Pro: Glossary of Terms
Internet Forums
Help is always just a few clicks away on the internet forums where experienced Ersky9x users
volunteer their knowledge and experience. Many of these people have been developing the firmware
for years without remuneration; all they ask is donations to fund further development.
Open RC Forums:
Ersky9x index page:
9XR index page:
Ersky9x and Eepskye are free open source software, independently developed. This manual is
provided to help you understand and use them specifically for the Turnigy 9XR Pro transmitter,
though much of the information also applies to the Sky replacement boards produced as an
upgrade for the 9x transmitter.
You can redistribute the software and/or modify it under the terms of the GNU General Public
License version 2 as published by the Free Software Foundation. You can also freely quote from,
redistribute and/or modify this manual; in doing so please acknowledge the source and any
The program and the manuals are distributed in the hope that they will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details. In using
them, you agree that you accept all responsibility.
For more information go to:
9XR Pro Ersky9x Explained 2014-05-13
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