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Dec 02, 2011, 04:08 PM
Registered User
Thread OP

interface to futaba TM-7 , TM-8 modules, how do you make it work?

hello all!

I am trying to use a futaba fasst RF module to act as my main RF transmitter in a project i'm working on. my goal is to omit the need of a hand held radio transmitter and just interface directly to the futaba TM-7 module

I am using a PC and (endurance R/C high resolution PCtx interface adapter ) to generate my PPM signal.

from reading over this site, I have found the pin outs, but cant make the module link to the receiver. when i power up the TM-7 and or the TM-8 on the bench, all i get is the following:

solid green and red LEDs for approx 1 sec. then alternating, flashing red and green lights. The documentations states "that there is an RF condition nearby". Am I missing something??? I have also powered the module in 3 different geographical locations just in case there really was interference.

1. has anyone else seen this issue with the alternating lights @ power up?
2. how were you able to resolve it?
3. in order to use the TM-7 (or any Futaba module) in this fashion are there any timing or sequencing requirements? like the PPM signal must be present during the module power up? or does the TM module look for a PPM sync pulse or anything?

Thanks for your help! any info would be greatly appreciated.

Here is how i have the module connect on the bench.

pin out and levels.
looking at the back of the transmitter, antenna pointing away from you, flip for looking at the module

left side
#1 PPM
#2 switched battery positive
#3 RF good (pulled low through a transister when signal is present at the final amp)
#4 ground
#5 RF out
right side

1 =PPM in (active low pulse 5v level) coming from the endurance RC PCTx.
5v ___ __ ____ ___
0V |_| |_| |_|
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Dec 02, 2011, 08:53 PM
"Simplify, then add lightness"
You show an inverted PPM waveform(ie active low pulses). That would be correct for a Futaba trainer port, but I am fairly certain that the Futaba module needs active high pulses on pin 1.
Dec 03, 2011, 04:32 PM
Inventor&Genius Extraordinary
tune by tito's Avatar
you need a encoder for be able to send the channels with the endurance R/C high resolution PCtx interface, in all the videos at the Endurance PCtx interface web page they use a regular R/C transmitter, however you interface will work I think you problem is the power supply of 5 volts this voltage will activate the failsafe in the futaba transmitter mudule which operate at standard voltage of 11 volts to 8.5 volts when the alarm start to sound off to land a plane due to lack of battery power in the TX module, now I do not know if you are trying to power up both TX at the same time this will create you "RF condition nearby" , also I did check futaba for the power needed by the TX module however the spec. only say the module need 150miliamps but not voltage spec. only for the RX 4.8 to 6 volts.

Best Regards Tito
Dec 05, 2011, 08:29 AM
Registered User

Help Receiver Hacking Hitec Aurora9 (PPM) and read PPM By Atmega

Please help me.
I want to hack into remote Hitec Aurora 9. And the receiver output will be as Pam. And then read by the Atmega using C language and can drive the motors.
The choice of this method is due to limitation number of micro-pins.
I get the hacking and remote ppm and programming help ..
Thank you very much

Email : [email protected]
Dec 07, 2011, 04:07 PM
Registered User
Thread OP
Thanks guys.

I verified that the ppm was inverted. so i made an inverter for the PPM. its now 0v level plusing to 5v

0v___| |___| |__

unfortunitly when i power up the TM-8 it still goes into this flashing red / green mode.
here are the power up condishions.

1.endurence RC PCTx connected and outputing PPM 5V to 0v pluse
2. PPM inverter powered and inverting PPM to 0v to 5vdc pulse powered using 9.6Vdc
Dec 07, 2011, 05:51 PM
"Simplify, then add lightness"
Don't know anything about the FASST modules, but in the HF modules the RF Good pin is driven with an open collector transistor in the module and there is a pull up resistor in the transmitter. It is a long shot but maybe the FASST modules look for the pull up and you are showing a pull down.

The only other thing I can think of would be some kind of timing difference between the PPM signal put out by the endurance unit and the signal the module is expecting from the Futaba transmitter.
Dec 09, 2011, 02:36 PM
Registered User
Thread OP
Update! - I got it to work!!!!!

so long story short, i botched my inverter circuit, when i placed the components on my proto board, I misplaced the ppm out wire to the TM-8 and i had my scope on the collector leg, so on the scope everything looked good as i was beating my head into the wall.
so to recap this is what I verified relating to the TM-8 / TM-7 futaba FASST module.

1. TM-8 module operation voltage range - the module definitely functional between 9.6Vdc and 4.9Vdc. ( futaba uses a Sharp pwm regulator. input v= +30 to 5VDC. I would not recommend using any supply over the proven 9.6 unless you verify the input side of the TM-8 can Handel the voltage.)

2. IF the TM-8 module is supplied power, +9.6 to 5vdc but there is no PPM, alternating, flashing red and green lights are normal.

3. Proper PPM signal must be present at or before the time the TM-8 is powered. If the signal is interrupted or not present at power up, alternating, flashing red and green lights are normal.

4. when connecting directly to the TM-8, the PPM pulses need to be pulled high. our ppm is 0v to +4.3v

5. Pin 3 on the TM-8 serves no purpose for me at this time. pulling the pin high or low using a 10K has no effect.

I will post a schematic of the inverter circuit once i get home.

Thanks for the troubleshooting guys!!!
Dec 13, 2011, 11:54 AM
Registered User
The PIPE's Avatar

On using a TM-8 with a non-Futaba radio...

Dear Zellis:

The PIPE Here...just spotted your thread on using a TM-8 FASST module with a non-Futaba RC "virtual" radio of your own design of a sort, and since I've always built ALL my own RC gear since 1977 - because I HAVE to fly with those so-called "knobby" single stick radios - I've been quite "high" on the use of what's turned out to be the single greatest item ever designed to help in crafting one's own RC transmitter, that I've ever seen, Gordon Anderson's MicroStar 2000 encoder, described at his site at .

My FIRST pair of knobby "MS2Ks", the usual abbreviation for the MicroStar 2000 for its users, like yours truly) are meant to be on 50 MHz only, as I've had a Ham license since 1978, and Gordon himself designed a 50 MHz synthesized RF board - which I have two of, built and ready-tuned for use - to use "hand-in-glove" with his MS2K encoders. THe SECOND pair of MS2K knobby radios I'd like to build someday would, however, are meant to be used only on 2.4 GHz SpredSpec frequencies, and the Futaba FASST setup seems to be the best one to use for such an owner-built 2.4 GHz transmitter, especially with an MS2K encoder at its heart.

I've read just about EVERYTHING on the Internet about crafting such an owner-built radio using the MS2K/FASST combo for the choice of encoder and RF deck, and the usual advice on how to set things up goes as follows:

* The MS2K encoder's "sync pulse" timing MUST be set to 400 ÁS (microseconds) for any Futaba RF module to "listen" to an MS2K encoder...

* The minimum "servo timing" (width of the servo pulse) cannot be any shorter than 0.90 mS (milliseconds) on ANY channel in the transmitter, for the FASST module to understand the signal.

I noticed you were quite apprehensive on powering up a TM-8 FASST RF module with anything more for supply voltage than a 9.6 volt nickel-chemistry "eight-cell" battery pack. Be advised, though, that when such a pack is used IMMEDIATELY after taking it off charge, the Tx battery pack voltage can be as high as 11.1 volts - remember, this IS for an eight-celled nickel-chemistry (NiCad OR Ni-MH) transmitter pack - I would certainly think that you'd be able to quite SAFELY power a TM-8 RF module with as much as an eleven volt DC voltage level.

Also, where a growing number of my fellow MS2K users over at at Yahoo ARE considering using a trio of A123 System's lithium iron phosphate (LiFePO4) cells (like the ones available at ) for their Tx packs - which put out a nominal voltage of 9.9 volts (3.3 volts per cell) for a complete "3S1P" trio of cells in such a battery pack - such an alternative lithium-iron-celled battery pack in place of an eight-celled nickel chemistry battery pack-powered RC transmitter, should ALSO be quite safe to use with the TM-8 FASST module.

Thanks to John Eyer from the Yahoo MS2K user group, who measured one of his Futaba 50 MHz FM RF modules' main case, he found it to have the following exterior dimensions to its plastic rectangular main case...

Overall Height of 59.0 mm, or just over 2-5/16ths inches high
Overall Width of 37.4 mm, or just under 1-1/2 inches wide
Overall Depth of 19.7 mm, or just under 25/32nds of an inch deep

I was wondering if your TM-8 module MIGHT just have the same EXACT dimensions as the ones quoted immediately above, not including the attached antenna OR any of the antenna's support structure on the outer surface of the module. If you've got a chance to have the time to do it, please check your TM-8 module when you've got the time to do it, to see if it HAS those same dimensions by measuring it yourself, to see if it is indeed a match to the measured and listed Futaba FM module's main case's dimensions.

In closing, the MicroStar 2000 encoder is also the MOST versatile encoder unit thatI've known to ever have been offered to those of us who build all their own RC radios, and also for retrofitting a beloved, older RC radio to have the same functionality - or BETTER functionality, in some key respects - than any existing factory-built RC radio on the market.

If you're able to, and have the time to do it, please give your TM-8 module a "careful measure" for its outer dimensions, and perhaps, if possible, please take a digital photo or two of its rear surface, to get a really good look at its electrical connector. My FASST-dedicated future MS2K encodered transmitter design project is only in the CAD drawing stage on my home PC at present, and getting a photo or two of the TM-8's electrical connector block, and exactly WHERE it's situated on the rear surface of the TM-8 module itself (as well as the TM-8's main case exterior dimensions) would be very greatly appreciated.

Best of luck on your project, of course...and you'll also be able to help my fellow MS2K-based transmitter builders and owners, if you get a chance to please measure up your TM-8 module when your time permits, and please share those photos and measurements with the rest of us at RCGroups when you can.

Thanks in advance, and Yours Sincerely,

The PIPE....!!
Last edited by The PIPE; Dec 13, 2011 at 02:43 PM.

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