APM 2.5 plus the 3DR radio telemetry works great, now I want to add my MinimOSD board.

The MinimOSD board reads MAVLink messages from its RX pin and request rates from APM on the ArduPilot "telem" port. (Port 0 implied). The APM2.5 board 3DR radio connector (UART0/2) pin out from the board edge counting inward is: Gnd, (blank) RX, TX, +5V.

The MinimOSD Introduction has a diagram which states APM telemetry port (pins sequence from bottom) (shows bottom of block diagram of Port) This presumes that it is also board edge of back of APM2.5  and shows (APM pins) counting inward as:  Gnd, (space) +5v, out, in.  (out to rx of OSD, in to TX on OSD). The silk screen on the APM2.5 is clear, and I believe +5v is the most inside (away from edge) pin of Port 0. Should I just wire my OSD up based on what the APM says about Port 0 pins?

Is the diagram in MinimOSD introduction wrong on its cabling to APM telem port?

I am eager to add my MinimOSD to my build, but do not want to fry or brick my OSD.

Hope this helps someone in clearing this up somehow.

It would have been handy to have had another connector like 3DR for the feed to the MinimOSD.

In the meantime I guess I just hack into my 3DR cable or solder to tiny pins on back of APM2.5.

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I just connected my 3DR and MinimOSD to my APM 2.5 a couple days ago and have it working.  I am finding it hard to follow what your describing but I will try and help.  

I have my 3DR soldered into the UART0 pins.  I then have my MinimOSD soldered onto the underside of my 3DR radio without the OSD's TX connected.  Both boards of mine are labeled clearly what is G, +, TX, and RX I just soldered to the matching location on each board as described above.  on the MinimOSD i used the.

If you want some pictures I can get them later tonight.

Cut myself off there.  So I'm using GRN as ground for some reason (I rewired it and screwed it up is the reason) but it seems to be working.  I will wire it up differently and give an update later on.


I appreciate all of you who contribute here. I am very new to UAV/FPV and would like to contribute some of my findings.

 I've recently successfully installed APM2.5 with the 3DR Telemetry radio and MinimOSD. There are only three wires needed to connect the MinimOSD to the 3DR Telemetry radio:

The +5V OSD is connected to the +5V going to the 3DR radio. (To supply power to the OSD)

The OSD GND to the 3DR radio GND

The OSD Rx to the 3DR radio RX (They both receive Tx messages from the APM)

That is it, three wires. I clipped the miniature 5 pin connector from the cable supplied for the MinimOSD and directly soldered the wires described above to the corresponding 3DR radio pin remnants. The nice silkscreen labeled pins on the circuit boards will help guide you.

I hope this helps some of you.


Well, I know now why I need glasses....   Found the Uart 0 pins on the opposite side of the apm

labled UART 0!  Just had to solder three wires in there to gnd, +5 and TX. Could have used a 3 pin header

but wanted minimum possible loose connections while flying. Just look down at the bottom rear of the APM 2.5 board near the 3DR symbol. Got my OSD running but had to download the new firmware. Seems the minimOSD is shipped with the older firmware which runs with APM1 and Mav 9, APM2.5 runs Mav 10 and will work if you follow the directions to update its firmware.

Enjoy, I know I am!

Thanks Larry for the information. Maybe I can clean up my installation  the way you mentioned. I didn't even notice the points on the board that you described. I did update the firmware before spending a considerable amount of time learning how these things work. It always seems these projects exact a certain amount of cussing to see them through, however, this is a good thing!


I would really benefit from some pictures of this. I am a little confused as to weather I should tap into the cable with pre-made plug provided with the 3DR Tx, which connects to a tiny plug (labeled UART 0/2) that I could never successfully solder to, or tap into the wires connected to that plug...or solder directly to the other set of holes labeled UART 0/2 on the other end of the board. 

Thanks in advance!

Hi Brenden,

I'm sorry I cannot provide you with a photo, however, I can tell you that I cut the mini connector off of one of the 5 wire UART cables, then stripped the ends and soldered them directly to the connector pin remnants on the underside of the 3DR telemetry radio. Another post here suggests soldering directly to the board as in the latter location you described in your post.



Logically, Minim OSD and 3D Radio will connect in parallel. 


All you need to do is to ensure that you do not connect the Tx wire from Minim OSD to anything.


Minim Rx  to 3DR Rx

Minim +ve to 3DR +ve

Minim -ve to 3DR -ve


After making the connections one thing that boggled me for a few hours was I received all zero's except for the flight mode I would set.  Turned out you need to have the receiver side of the Telemetry module plugged in for the OSD to pickup the info otherwise you would need to plug into the TX wire.

I've just come across this same issue as you Steve, and it's very frustrating! I have my minimOSD and 3DR radio connected in parallel to the same port, and the tx connection on the minimOSD is disconnected.

I don't always take my laptop with me when I fly, so when I took my quad out today by itself, I got my minimOSD overlay up, and it was showing it was receiving mavlink heartbeats, but none of the data would update, except for the flight mode. It's only when I got home that I realised that I now need to have the receiver module plugged into the laptop, and then be connected to mission planner before my minimOSD will update like it should.

Is there a way to fix this? The OSD should always work regardless of whether there is a ground station connection.

If you want your OSD to work without the 3DRadios, you have to connect it's TX line to UART0 RX.

Either install a switch on the OSD TX line, or plug it manually with a dupont line.

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