A quick graphical view of mixing:

The following is derived from

DX9 mixing has the following parameters

  • Master channel
  • Slave channel
  • Rate: <high percentage> <low percentage>
  • Offset: <percentage>
  • Trim: <INH/ACT>
Mixing allows control input for a channel to affect more than
one channel at a time. Mixing functions support:
• Mixing a channel to another channel.
• Mixing a channel to itself.
• Assigning offset to a channel
• Linking primary to secondary trim.

These mixes are available for each model memory:
Select a channel for master and slave. Inputs for the master
channel control both the master and slave channels. For example,
Elevator to Flap makes elevator the master channel and flap the
slave channel.

Change the offset value to move the effective center position
of the slave channel. Positive or negative value determines the
direction of the offset. Offset is not available for curve mixes.

The above offers almost no explanation of how the numbers really work.

What is really going on.

The master channel is the control channel. It's current absolute value (from -150 to +150) is what is important here. The slave channel is the control channel being altered. It plays only a "carrier" role of the output value from the mix. The mix value derived from the master channel is simply added to the output value on the slave channel.

Think of the high rate percentage and the low rate percentage as the value the mix will have if the master channel is at +100 and -100 respectively. When the master channel is 0, it will have a value of 0 (irrespective of these other rate numbers). The adjust value of the mix changes linearly as the mix channel moves from centre to (OR PAST) either of these end points.

Offset is where it becomes tricky. Offset is how far to move this entire range so 0 has no change. This is where most peoples brains explode or implode.

If we have an offset of 50, The master channel must be at 50 for no change to slave channel. With this same offset of 50, if the master channel is at -50, the low rate is applied. With this same offset of 50, if the master channel is at -100, 1.5 times the low rate will be applied. With this same offset of 50, if the master channel is at +100, 0.5 times the high rate will be applied to the slave channel; i.e. if you have a mix of high 10, low -20, offset 50 and the input channel is -100, the output channel will be adjusted by -30.

Last point is that mixes are applied cumulatively. If you have two mixes that affect the same slave channel, both output changes will be applied. That changes will be applied in the order of the Mix configuration; i.e. Mix 1 is evaluated first, then Mix 2 (and so on). One other note on this is that all mixes occur to channel outputs and are not available as master inputs for other mixes; i.e. if Mix 1 changes Aux2 output, and Mix 2 uses Aux2 to change Throttle, the alterations to the Aux2 output will not be used for the Mix 2 input (as it uses the source Aux2 value).

If trim is enabled, then source channel trim is applied to the master channel before calculating the offset on the slave channel.

This information was originally derived from the DX8, but the DX9 has more options for mixing such as activation by switches and curve mixing.  Curve mixing cannot use offset.

-- Question Dual motor throttle cut programming (from RC Groups)

{sigh!} I know there must be a way to do this, but I can't figure it out, so I come here asking for help.
I have a Dx18g2, and an AR6115e on a little twin electric flat foamie. I put the throttles on separate channels (THR & AUX1) so I could mix differential thrust. I got that working fine, but I'd like to make the throttle cut (Which I have on switch H) working on both ESC's. Right now, throttle cut only affects the throttle channel, the AUX1 output still responds to throttle stick movement even when the throttle ch output is stopped by throttle kill.
If it matters, I have the diff thrust mix on a switch I can turn on and off on another switch. I assume this will involve another mix applied to switch H(my throttle kill switch), but can't figure out how to make a mix that will freeze a channels output?
Thanks in advance for any help!

-- Answer from Andy

There is no mix to "freeze" an output (by "freeze" I assume you mean it stays where last put by the stick). You can create a set of mixes to perform the same function as ThrCut, though.
First you need to go to Channel Assign and set AUX1 input to INH.
Mix THR > AX1 at 100/100%. Set "Trim" to ACT so throttle trim is copied over. Set the switch so this mix is active when the throttle cut is inactive. When the throttle cut is active, this channel will now jump to the center.
To fix that position, mix ON > AX1 using the same switch but in the opposite state. Adjust the right "Rate" until the output shows the same position as the throttle in the cut mode.
You now have two throttle channels that honor Throttle Cut together. Note that ThrCut position only affects the THRO port. You need use the ON>AX1 mix to change the other throttle cut output.
Now you can do your differential throttle by having RUD > AX1 and RUD > THR as you already understand.

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