Using AP as OSD only - display all live parameters without arming

I’m trying a bit of a weird idea: I put an FC running AP on a plane that is RTF, the FC is not actually connected to any receiver or motors, only to balance port of flight battery. I just want to use it as GPS OSD, to see voltage, altitude, distance etc. (until I have time to convert the whole plane to AP).

The problem is that without being armed, the FC OSD keeps showing zero altitude. GPS data (speed, distance) is displayed. Is there some way I can force AP into showing baro data without being armed?

I ordered a PWM to PPM converter so I will be able to use a spare channel on the RTF plane’s receiver (Spektrum AR636) to connect to the FCs PPM input to make it arm, but it won’t arrive for a while so another temporary solution would be nice.

By the way, I also tried this with BF and INAV. BF is not showing any GPS data without arming, INAV also forces the altitude to zero before arming.

in your special use case as OSD only try setting ARMING_REQUIRE = 0.
mind that you should never do this once you‘re using your board for actual flight control, this is vital!
AP OSD shows alt above home, home position is locked when armed, the requirement to pass arming checks prior to takeoff ensures your FC is ready to fly with baros calibrated and a proper GPS fix.

Ha, I knew that AP would be the one that can do it, but I only thought of setting ARMING_CHECK to zero, which of course wouldn’t be enough in this case. Thanks!

needless to say that if you should ever get caught with an arming parameter set away from default i will deny any knowledge of this case :wink:


No chance, I just took a screenshot, printed it and will have my lawyer put it in his document safe. :smile:

Well, I celebrated too early. For this task I’m using only a cheaper FC (Matek F411 Mini SE), and that one is not in the firmware list. :neutral_face:

So I’ll be going back to BF and wait for the converter, but I think this is the last time I bought an FC before checking AP compatiibilty… Because this happened to me before, just a few weeks ago.

this board is not supported due to its limited memory size. ardupilot fits 1MB boards with just a few optional features disabled, 2MB boards allow the full set of features with plenty space left.
omnibusF4pro imho would be a pretty cost-effective option if you‘re looking for ardupilot compatible hardware that integrates onboard OSD, baro and full batt monitoring and optionally runs BF/INav too.

Yes, I went through the list and came to the same conclusion. But this FC was even 10 bucks less with a discount, no risk of bad clone since it’s Matek, and most of all, it’s already nicely attached to the plane now. But next time I want to do something like this, I’ll choose the Omnibus.

As for full feature set - I recently replaced an F722SE before I even started building, because I found out to my surprise it doesn’t have enough memory for AP, in contrast to its predecessor F405. Hope that’s not a trend - even now I won’t have all features with a Kakute F7. But it looks like unless you go for clones, a Holybro Durandal would be required, at nearly 4 times the price of the Kakute, and that’s too much for me. :wink:

there‘s a summary of memory-dependent limitations in the wiki:

depending on your individual requirements there‘s a number of affordable hardware options. for recreational FPV applications, i personally wouldn‘t want to go back to boards requiring an external OSD and battery monitor.

Oh, I hope the exclusion of I2C barometers does not apply to Kakute F7 AIO V1.5? I was planning to to put at least one extra barometer on the craft as temp sensor…

TBH, the thing I miss the most when running AP on “mainstream” FCs are WS2812 LEDs. :wink: Of course they’re only a gimmick but I just became used to them, since it was always just a few clicks in BF (or INAV) configurator to customize them. But no problem, I got some “self-flashing” LED strips for future AP builds!