I discovered this when removing OSD's TX pin  - APM 2.5 fails to boot if OSD is disconnected or it's TX pin disconnected. (MinimOSD)

By fails to boot - i mean no servo movement in manual mode, nor any movement when switching to other modes.

if booted on USB, then connected to servo power, everything will work. (except OSD)

The OSD is connected using the small to dupont-5-pin connector.  - and yes, I did try to remove the fifth pin (not sure why APM2.5 has it.)

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –


  • I have a same problems. I have to connect OSD or XBEE before board can boot up. And I wonder why no one from development team answer this question.???

  • update, connecting a 3DR modem - works too, - it's like something "must" be connected to the RX pin on the APM's telemetry port, if nothing is connected - APM will not get ready.

This reply was deleted.