Is it necessary to (update)flash the Atmega32U2 (PPM encoder) on an APM 2.5 if using a Futaba system?

I'm constantly expanding my understanding of all the options and systems within the APM 2.5 by re-reading the wiki and looking for things that have changed or things that I hadn't considered before.

One thing that has recently caught my eye was the section here in the ArduPlane wiki titled

'How to flash the Atmega32U2 (PPM encoder) through USB'

The downloads section title description states

APM 2.x ArduPPM Firmware v2.3.13 (recommended update for Futaba radio users)

The wiki page was most recently updated almost a year ago (Dec 29, 2011) and doesn't specify what versions it applies to.....I don't know why this text is coming out italicized....I don't have Italics on...anyway the wiki instructions specifically refer to APM 2.0 not 2.x and the images are all of an APM 2.0 board. I realize that this is just a representation of the board at the time but it doesn't
make any reference to APM 2.5.
The downloads section here states
ArduPPM v2.3.13 ATMega32U2 firmware for APM 2.x

So is the upgrade necessary for APM 2.5 or not, and is there a list of Futaba receivers known to
n issue with the stock PPM encoder firmware? So perhaps if someone could clarify this itwould be great, also are the instructions in the wiki still applicable to an APM 2.5?
Nathaniel ~KD2DEY

Views: 6998

Reply to This

Replies to This Discussion

I've also experienced problems with th R6008 receiver (in normal speed mode, not high speed) and the 3DR PPM encoder.


Yeah that's the standard receiver that ships with the Futaba T8FG Super 14 channel system. Personally I haven't noticed a problem yet, but I don't expect it would be as obvious in a fixed wing system. I'll be updating the encoder just to be sure.



Nathaniel ~KD2DEY

With the Usb connector on my APM2  trashed  I will have to pull the board and solder the isp header to update the PPM encoder. 

Are all Futaba radios  seeing the glitches?  The discussion had reference to some receivers  not displaying the problem. My FS617 receiver   in 7Ch mode  did not  have  motor  log spikes last  time I looked at the logs.  Does it just happen when CH 6 or 7 are used ?

In my experience it occurs on Futaba receivers with 8 or more channels. Maybe not all, but I've only tested a couple. I've never seen it on a 7 channel or less receiver.

Based on what I've been able to find on Futaba's website I would suspect that the following receivers when used with the compatible transmitters (most but perhaps not all of which are listed following the list of receivers) outputting in either MULT or MLT2 modes will experience the same issue with the PPM encoder on the APM 2.5.

Receivers: R608FS, R6008HS, R6014FS, R6014HS, R6108SB, R6208SB, R6203SB, R6203SBE, R6202SBW, R6303SB, R6303SBE

Transmitters: T8FG, T8FG SUPER, T10C, T10CG, TM14, T18MZ, T14SG

If you have one of these Receivers/Transmitters and can cofirm or add to this list that would be great!

I can confirm that the R6208SB that ships with the T8FG Super does in fact have an issue with ArduPPM firmware before 2.3.13.


Nathaniel ~KD2DEY

Drone Savant,

Follow the link on Steve's reply Pg1 of this discussion and you will find many good descriptions of what occurs if and when you are having a problem. I don't think this is a problem that could have been foreseen or prepared for as it has to do worth a non standard output on some very specific receivers.

It wouldn't be a bad idea though to have a sketch that could read the incoming signals and determine if your receivers output is compatible.


Nathaniel ~KD2DEY

I assume this is all for 2.4GHz Futaba radios and doesn't affect any of the older 72MHz stuff right? I just ask because I use a 9C for FPV work and will be installing the APM 2.5+ in a plane and tricopter. From what I gathered, it's likely only a newer 2.4GHz issue but it would be good to know if I really need to care about this.

I used Spektrum for any of my 2.4GHz stuff so at least that shouldn't be affected.

My list is based on some assumptions so take it with a grain of salt, and don't think that it is an all inclusive list. As far as I know this is only affecting newer receivers and yes they all are 2.4 GHz. That is not to say that there couldn't be any issues with some 72 MHz system out there. The issue is really with the receivers however the receivers listed ship with the transmitters shown so they are related. The best thing to do would be to view your CH input and output in the MP with the tuning option checked and look at the signals over a period of time say maybe an hour? If your traces don't exhibit any spikes you can't explain then your probably OK. Either way there really shouldn't be any negative to updating the firmware of the PPM encoder. So if you want to be sure.....upgrade it!


Nathaniel ~KD2DEY

No, it's just the latest 2.4GHz receivers (released in the last year?) with more than 8 channel. It doesn't affect any of the Futaba gear I've got, which is mostly 7C. 

In my opinion unfortunately there is not a rule, may depend on the rx firmware, Orange Futaba and FR-Sky TFR8 (is the same rx) cause these problems here, tested with APM2/2.5 in different setup.
For this reason owners of Futaba update you encoder whatever, with the new one the problem is completely gone here.


I agree that the list shown in this post isn't complete, and may not be considered accurate until people add confirmed receivers to the list. I disagree however that there isn't a 'rule'. In my opinion this problem seems to affect any Futaba compatible receiver working in either MULT or MLT2 mode which makes the capable of reading a signal containing more than 7 channels. I thinks that all S-Bus compatible receivers and any native 8 channel Futaba compatible receiver. However until we start to see a list of confirmed receivers and the Transmission mode they are being used with it's only an opinion.


Nathaniel ~KD2DEY


I agree. I first experienced this issue with the standalone 3DR PPM encoder more than 18 months ago, so the myth that it's only recent/newer receivers is also flawed. If it's FASST and 8 channels or more (thus being MULT or MULT2) then multiple servo outputs will be updated at identical times. The degree to which the issue manifests will of course vary depending on numerous factors.

Reply to Discussion


© 2018   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service