Futaba 12FG Programming Notes

Mike Shellim, 10 Jan 2008

Introduction

While I was writing a full review of the Futaba 12FG (published in RCMW March 2008), I came across a few programming issues. Amongst these were the undocumented LINK option, and limitations of the servo assignment feature.

The LINK option

In the programmable mixer screen, both the master and the slave have a LINK option. This seems to be a means of daisy chaining mixers together. The Multiplex 4000 has this capability (dubbed 'Multimix') and it can save a lot of programming on complex gliders.

However LINK is not properly documented on the 12FG and it took me a lot of fiddling around with my ServoSim channel visualiser to suss out how it works. You may come to the conclusion, as I did, that the LINK option is pretty well unusable as currently implemented.

I believe the following is correct, but if you can add to it, please let me know .

General

In the following description, the Link state is 'active' if it's set to either - or +, and 'inactive' if it's set to OFF.

Link option for Master

If the link option is active against the Master, then at any instant the master input M will see the sum of the following values

The value of M (i.e. the position of the control stick, optionally taking into account the trim position and AFR), plus
the sum of all the mixer outputs which (a) have M as their slave and (b) have their output exposed (see below).

If the link option is inactive, then the master input M will only see the value of input M.

Link option for Slave

If the link option is active for the Slave field, then there are two distinct and separate effects:

The mixer output will be exposed to other mixers (see above)
The mixer output will be sent to all related channels, not just the primary channel. So for example if there four aileron servos, the output will go to AIL, AIL2, AIL3 and AIL4.

If the link option is inactive, then

The mixer output will not be exposed to other mixers
The mixer output will be only be available to the primary channel e.g. AIL, (not AIL2, AIL3 etc.)

I have to say this is all very poorly designed. How on earth is the average user to make head or tail of this?

Assignability is limited

The assignability on the Futaba 12FG is not quite as flexible as the FUNCTION menu would suggest. While the menu appears to allow total flexibility, sometimes an assignment will work, and sometimes it won't.

In particular, assigning subsidiary functions like AIL2, AIL3 etc. won't work unless these assignments are supported in the selected model type. For example, you cannot assign a servo to AIL2 unless the active wing type supports two or more aileron servos.

Apart from being rather restrictive on such a high end set (and there is no 'universal' unrestricted model type available as on the Multiplex mc4000), the way it's handled on the 12FG is another example of poor design. If a feature isn't available, it should be disabled in the user interface, or a warning should be displayed.