The very first S/C emulation encoder I ever did, back in 2009, used a Futaba 6EX FASST RF board and 415uS pulses. This was prior to the Frsky betas and was the forerunner to the current S/C encoder, the one demo'd to Shaun in 2009. I remember the secondhand FASST board was expensive, but it was early days.
On the 2.4 FASST RF board Futaba use the PPM pulse width (which if course isnt normally part of the timing) to control failsafe position and RF output power, so you need to replicate the 'normal' mode pulse widths.
I based the 415uS timings on the Multiplex project "Legacy Radio Going FASST" documented on RC Groups in a thread started by Julez in 2007:
https://www.rcgroups.com/forums/showthr ... ransmitter
It worked perfectly but I never flew it, I was never confident with the PPM constraints, even though they got away with a very crude 555 timer arrangement in their version 1. In fact I still have it in my stash somewhere, and also a couple of spare FASST boards. The article does state that PPM polarity doesnt matter.
If you notice, in the Attiny version they use the schottky-diode method to emulate an open-collector drive, just like we had to do with the V8 Frskys and the Coronas. The 555 version is simply 5v PPM pulses via a 1k resistor (which I think is what I did). All my pulses were fixed at 415uS, no variation, so it was permanently in 'normal' mode - no failsafe or low power. I think it worked ok with just 4 channels. My old PIC experiment appears to be a 'work in progress' as compound mode sends 4 channels and sequential sends 8 - must have been some sort of channel count test I was doing at the time.
Here are some notes I copied from somewhere (it was 11 or 12 years ago...)
It suffers from a bit of dodgy translation... but the jist is there
Code: Select all
<400us Transmitter remains in the operational error flashing mode
400-420uS operating mode with no fail-safe
425-440uS secure Failsafe mode with adjusted Failsafe value on channel 8
445uS Transmitter diodes flash, when like if them in the power down mode
would be. Whether that the case is real could not because of to large housing
ranges despite walls not be verified. And also not yet whether that switches
off automatically power down. The second COUNT down bleeper does not
function anyhow
Whether o.a. the values still tension and temperature influences are not subject
are at present well-known. Since it more meaningfully is rather in " for problems;
Not Failsafe" - " range as in; PowerDown" - Range to come is recommended the
pulse width rather to the 425µs to select thus approx. 430µs and NOT 440µs.
Attention, from this follows because of " Battery Failsafes" in the receiver:
If Failsafe generating pulse widths > 420µs is transferred, is it because
Grundsender longer impulses has or evenly a inpulsverlängernde circuit is
used as by Christian. So 3 compellingly gas/Steller must be attached to plugs.
If the elevator would there e.g. be as with Graupner, with receiver undervoltage
on one for the model lethal excursion would be rather surely. Means vice versa:
If one wants to use such T6-Adaptationen with the original model attitude
reached with 35MHz, the pulse width under 420s MUST be; thus like e.g. with
the simple inverter and the mc22.
72=450
70=435 failsafe works, low power
69=425 failsafe works, full power
68=420
To be honest its all a bit hazy now, its been so long since I used a commercial radio that I cant even remember how to bind a Futata FASST receiver.
It is perfectly doable, just dont go below 400 or above 425 uS, but its a lot of faffing about compared to current modules
EDIT:
Hi Max, I'd nowt else to do tonight so I dug out an old FASST RF board, patched the 12-year-old fasst variations into the current S/C encoder, and it works great. The green LED on the fasst board indicates that its in full power, 'normal' mode which is good, and this confirms that four channels of positive-going PPM with 415uS pulses works just fine. It wasnt as much of a faff as I remembered after all. The main board of the 6EX is actually a carrier, if you were enthusiastic enough (I'm not) you could separate them and just use the smaller board. You'd have to provide the regulated 5v of course, and the two leds. The arduino could supply 5v straight from the rail (if it has the larger regulator). I didnt bother, I just wired the carrier board.
I'd say its definitely a go-er. In fact I might use it for a project - I've a few R617's.
Which encoder is your friend going to use?
the 7ch update optionally does 400uS or is easy to change to 415... likewise the Reeduino is easy to change too.
Cheers
Phil
Cheers
Phil