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Programming the Taranis Q X7 Transmitter for Combat Robotics
The Taranis Q-X7 with OpenTX 2.2 firmware is a remarkably flexible transmitter that can adapt
to very sophisticated control requirements. Unfortunately, all that flexibility comes with a
complex user interface that confuses novices and gives experienced R/C jockeys a bewildering
range of choices. For example: you can't simply turn on Elevon mixing – you need to build up a
channel mix from the elements available to the transmitter. This takes some thought and
planning.
While there is ample documentation available on the web to explain in detail the theory and
practice of OpenTX, two things led me to write this guide:
1. OpenTX was not developed for combat robots. The available tips and examples are
typically designed for servo-driven mechanical aircraft control surfaces that have
different considerations than do the Electronic Speed Controllers used in robot drive
trains.
2. The basic requirements of setting up a robot drive train and typical weapon control are
relatively simple compared to the capabilities of OpenTX. A robot builder shouldn't be
forced learn the full scope of the firmware capability simply to get their robot operational.
This guide will skip over the bulk of the theory and provide examples of set-up, tuning, and
troubleshooting for standard combat robot layouts. Once you have your 'bot operational you can
take time go as deep into control theory as you like.
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Summary of Contents for taranis Q X7
- Page 1 Programming the Taranis Q X7 Transmitter for Combat Robotics The Taranis Q-X7 with OpenTX 2.2 firmware is a remarkably flexible transmitter that can adapt to very sophisticated control requirements. Unfortunately, all that flexibility comes with a complex user interface that confuses novices and gives experienced R/C jockeys a bewildering range of choices.
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Page 2: Physical Setup
RCdiy Taranis Q X7 OpenTX –Setup http://rcdiy.ca/taranis-q-x7-tutorial-first-flight-setup/ As delivered, the Taranis Q-X7 defaults to the ‘Mode 2’ stick layout with channels one thru four assigned to Aileron, Elevator, Throttle, and Rudder (AETR) in that order. This stick and channel layout can be changed, but the examples in this guide assume that this default channel layout is your starting point. - Page 3 A quick tap on the MENU button (≡) will take you to the Model Setup menu. If you hold it too long you go to the Radio Setup menu -- just a tap. Now tap the PAGE button repeatedly to flip down thru the screens.
- Page 4 responds to Aileron input by default. We will insert an additional line in the mix to add Elevator response. On the MIXER screen: Use the scroll wheel to highlight the line, then long-press the ENTER button to bring up an action menu. ...
- Page 5 Your MIXER screen now looks like this: There may be some clean-up to the response directions based on motor polarity that we’ll sort out in the troubleshooting section, but that’s our mix. NOTE: For aircraft applications, an Elevon mix will typically ‘Weight’ the mix elements at ‘50’...
- Page 6 You could assign any unused switch to control -- but is a momentary switch, spring- loaded to return to its default state when released. That makes it perfect for triggering a flipper. The INPUTS Screen -- Adjusting Control Response Time to do some work on the INPUTS screen where we have the option to modify the signal coming from a stick, switch, or knob before it gets to the MIXER screen.
- Page 7 Adjustments to the Weight of the Aileron stick here will affect all uses of the Aileron input in the MIXING screen. It’s easier to have only one place to make adjustments to steering sensitivity. Adding a Dual Rate Switch We’ve reduced steering response to a more comfortable level, but there are times when it would be useful to quickly restore full rotation speed -- maybe for a simple victory dance, or maybe to spin fast enough to flip back upright when inverted.
- Page 8 How does this work? If there are multiple lines entered under a single input, the transmitter evaluates the first line to see if any conditions it includes are met. If they are, that line is used. If not, it skips down a line and repeats the evaluation process. ...
- Page 9 I’ve arranged the topics in this guide to mirror the order of progression a robot builder might follow in setting up a Taranis Q X7 for their use. At this point it would be helpful to follow a position signal all the way thru the transmitter to better understand the ‘big picture’.
- Page 10 extended at +90% servo motion. The servo will ‘stall’ if commanded outside this range, and stalling is hard on a servo. We can limit the range that can command to prevent servo stall. Page down thru the Model Setup menu to the OUTPUTS screen. With default settings your outputs screen should look like this: The OUTPUTS screen allows direct limiting of the motion range commanded on each side of the motion center point.
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Page 11: Channel Reversing
Bonus Content By default OpenTX prevents assigning Output travel values outside the range of -100 to 100. However, most servos are capable of responding to signals outside this range to provide an extended range of motion. If you require increased extension from a servo you can over-ride the default limits on the Model SETUP screen: Page upward from the OUTPUTS screen multiple times to find the SETUP screen. - Page 12 Your OUTPUTS screen now looks like this: The change to the screen is subtle: the little arrow to the right of the ‘100’ on the CH2 line now points to the left instead of the right, indicating in ‘inverted’ response. In the next section we will check the operation of the ‘Elevon’...
- Page 13 Summary and Additional Resources There you have it. We’ve only scratched the surface of what OpenTX can do, but the examples given here will suffice to get all but the most exotic combat robots up and running. Now that you’ve got a taste of how the firmware works you have a good base for implementing less common functions and features, like: ...