Discussion FASST-izing normal transmitter?

[Julez]

Hi!

A lot has been written about Larry Hilgerts successful attempt to spektrumize a normal transmitter, using a DX6 module.

I just had a look at the FCC test report internal transmitter pictures of the Futaba 6ch FASST transmitter. Here they are:
https://gullfoss2.fcc.gov/prod/oet/f...ive_or_pdf=pdf

FCC ID "AZPTMSS1-24G".

To me, It looks like the FASST module samples the PPM pulsetrain.
When one looks closely, one can find the Futaba- typical 5-contact pin row which normally connects to the RF module.
At the transmitter PCB, "ground", "impulse" and "positive" are connected to this pin row, "antenna" is left out.

The other contacts are for 2 status LEDs and the "GENERAL-FRANCE" switch.

I guess, it should not be too difficult to transplant this module, what do you think?

[Silent-AV8R]

Given that Futaba has modules on the way for their radios my question is why would you bother? Might be a fun little science project, but other than that I don't see the point.

Also, I have not been paying attention. Is this even legal to do?? Here in the US we cannot swap a TX module crystal legally, so it makes me woner if it is OK to hack an entire RF section.

[village_idiot]

Looks like the only thing missing is the "switch" that pulls pin 3 to ground to turn on the RF "OK" light that my 9C uses. Looks like it is also small enough to put in a Futaba module.

[TheSteve]

I would think it will work. If you look at Futaba's first FASST system it was for the 3PJ/PK ground systems which use modules the same size as the 9C etc. I am thinking all of the modules are probably the same hardware with different software to optimize for the number of channels required.
Change the 5 pin header to a 5 pin socket and it might plug right in.(I'd verify voltages first though just to be safe!)

[Rudy Vienna]

Originally Posted by Silent-AV8R

Given that Futaba has modules on the way for their radios my question is why would you bother? Might be a fun little science project, but other than that I don't see the point.

One point you can find here: http://www.runryder.com/helicopter/t172571p1/

The variability in latency of two frames may be a Software-Problem of the TX.

But: the figures are for Heli and "Normal" channel 6, not representative for a not-heli. Channel 6 seems to be a pure mixing-channel with time-loss respectively (1 frame??).

I expect my ordered one (in stock) end of the month, so I can measure frametime and channel's 1-4 latency. And evaluate pulsetrain and synchronisation.

[Julez]

Hi!

Rudy just published his findings in Germany, and things are looking good. Most likely, one will be able to FASSTize normal transmitters, as the rf- board in the 6ex does in fact sample th PPM pulsetrain.

Should I get my 6ex this week, expect results this weekend

[Rudy Vienna]

So I have to hurry up today after the May Day parade, have I not?

mayday, mayday......

Rudy

[Rudy Vienna]

The T6EXP 2.4GHz latency, measured as a blackbox from stick to servostart:

- Channel 1 aileron, 76 readings:
min 13ms, max 35ms, medium 24ms, without servolatency 22.5ms.

Faster as DX7, 4ms slowlier as mc22/PPM

- last channel 6 switch, 74 readings:
min 18ms, max 38ms, medium 28ms, without servolatency 26.5msec.

- Tx-frametime 22ms mit 9 pulses für 8! channels.

Very interesting: Rx-frametime ist 16ms! This is an ample evidence for the fact, that there is no direct connection of the Tx-cycle and the Rx-cycle feeding the servos, if there is a memory in a Rx.
This 16ms is a rather safe cycletime for analogservos against overheating.
Using digiservos, the output cycle could be much shorter.

Rudy V

[Rudy Vienna]

Hi everybody,

since 8:30 UT is the connection of my fast mc22 (medium latency 18ms!) and the RF-part of the T6EXP 2.4GHz runnig well, without smoke, smell or any bad signs.
The Rx is dooing what it is produced to do: positioning servos without any glitch.

To understand what I did, watch the pics on that page, dealing with mc22 combined with DX6: http://members.aon.at/flug.fiala/dx6-mc22.html

3 issues:

1) There is no EIRP-reduction possible, because Futaba does that not similar to DX6, only during switch-on initialisation.

2) I have no idea, if rebinding will work correctly. The german manual says nothing about "Power down" during rebinding.

3) There is no engine-failsafe, all servos 1-4 in "HOLD"

And here some selfexplaining pics, please note the 2 green LEDs!

[Rudy Vienna]

Hi,

T6 RF + mc22 ready for take off, after closing the tray of course.
Antenna DX6

[Rudy Vienna]

1) first flights without any problem.
But feeling 'better connected'.

2) Latency variation of 175 samples

[Julez]

Bingo!

With the help of some bright fellows in Germany, I was able to build a pulsetrain converter.
It is a monoflop, which makes sure that the pulswidth is between 400us and 480us. The FASST module will not work with other pulswidths.

I managed it to jam all the stuff in my thrusty FC18, and now I can happily fly on 2.4GHz without having to use a transmitter below my needs.

Cheers,

Julez

[mhoyle]

Can you rob the Fasst R/F board out of a 6EX and make up your own module for a 9C for example, fitting a second Arial to the Tx or back of module
Whats the futaba pulsewith ?

[Julez]

Sure this is possible.
But with the dedicated FASST- modules being in stock now, I think they would be the best solution.

[mmormota]

I am about to FASST-izing my Evo 9.
I did some measurements. Here are the results:

Input signal: 8 channel ppm (9 pulses)
Amplitude: 3,3V, positive pulses
Frame: 22,5ms

Pulse lengths:

Pulse 1: 420us = normal power, 440us = reduced power
Pulse 2: 400us = failsafe on, 420us = failsafe off
Pulse 3...9: all cases 400us

I write a simple program for a small PIC to provide the proper pulses. A 9th channel tells the PIC the mode, this way no need for extra switches, mode selection can be done using the Evo widgets. Of course the PIC only receives but not transmits the extra channel.

I am curious if the dedicated modules input is PPM or PCM.

Some scope screens: