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

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No, that was most likely a APM control/mode logic flaw. I haven't been involved in that particular case, but I would be very surprised if it hasn't been fixed a long time ago.

A PPM glitch will recover the next radio input cycle, meaning that the throttle spike will only last about 1/50 of a second. Enough to get a visible shake in the copter, but nothing serious like dropping to the ground, or a runaway.

Great! Any feedback if very helpful and much appreciated.

Note to all, remember to specify relevant information like radio or transmitter module and receiver type when you post about a glitch.


Have you had a chance to take your bird out and test this Tx/Rx combination with the latest PPM encoder firmware? Just to be sure what Tx mode are you using? 7ch MULT or MLT2?


Nathaniel ~KD2DEY

i purchased 2 new apm 2.5+ units from 3dr store last week.... everything was installed on a pre existing quad test bed running perfect on the naza controller.... when apm was installed and tuned i get occassional motor spike and very occassional i get unwanted commands....  when sitting on my bench not flying every so often my gimbel will twitch.... showing its not the motors or vibrations causing this........


also when trying to flash the atmega chip per wiki... the unit connected by usb, installed jumper and shorted pins then trys to reconnect but fails and gives the computer the three sounds indicating failed connection..


so i can not flash my new apms.... now what can i do?


i lowered my mpuk to 20

every function works well in flight.

im running brand new futaba t8j radios with 8ch recievers.

any help would be appreciated

all my other posts went ignored so im trying it here.


626-789-4045 william

uav productions.... youtube

William, as I responded to your identical PM, please contact tech support and ask them if you can send the boards back to be reflashed with new PPM firmware. 

update...i found the dfu driver and installed it myself and now can connect to flipand flashed with latest hex.....

does anyone know if everything needs to be recalibrated on v2.9?

the radio or acellerameters ?

Hi all. How can you tell which version does the board have? Is there any software to check it? Thanks!

Hi Bernardo,

Yes there is! If you follow the instructions in the wiki here you can use the FLIP application to 'read' the firmware version of the Atmega32U2 chip.


Nathaniel ~KD2DEY

Any APM shipped from 3DR before March 4, 2013 has the OLD PPM code.  Most radios with 8 or more channels will probably have an issue.  I put a scope on my Spectrum 8 channel receiver and many of the outputs occur at the same time - thus causing a problem. My problem was random "mode changed to RTL" - just like some others experienced.  If you use ANY 8 channel radio - update if you have the older APM.

See here for the latest instructions. There are some words about determining what firmware is currently installed. The old firmware as no identification of the revision number. The correct ( and latest) firmware has the revision in the code so you can see it.

Crasher I'm new to all this so please bear with me . I have just purchased a APM2.5 board and flashed it with Arduplane 2.74 through Mission planner . I was going to use an 8ch futaba compatible orange 2.4ghz receiver , but found out about the problem with the 8ch rx's . Crasher are you saying swapping a 8ch 2.4Ghz rx for a 7ch 2.4Ghz rx would kept this issue from occuring ?

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