Here is something confusing to me........ My APM2 will not arm the motors until I push the reset button.

I use a 7.4v batt through a BEC to power the board. All of my esc's are opto isolated. I run a 5800mah 4s batt for the motors. I have powered the board both ways with or without the jumper through the input and output. The only way I can arm the motors is resetting the APM2 while the batteries are plugged in either by pushing the reset button or unplugging and replugging the APM2.

Any ideas?

I get this too, APM2 will not arm motors until reset button is pushed. Blue LED flashes then goes solid but red LED is off and stays off until reset is pushed.

Presumably you're using the latest version of the code from the mission planner?

Any chance you could provide a dataflash log? These can be downloaded through the apmission planner's terminal screen. Maybe one log of you being unable to arm the motors and one of it after you've pushed the reset button and are able to arm the motors.

It must be a timing issue. The question is whether it's a radio problem (i.e. the APM can't see the message in from the rx (unlikely) or it's the outgoing message to the ESC.

I have the same issue that reported before. I´ve noticed also that just after switch-on and having the issue, I connect to MP thru USB cable the issue is solved alone (red led start to work and then I can arm). I´ll try to get a log for you to study.

This has been reproduced by a good number of people including a few on the dev team. We know it affects arducopter more than arduplane. It's somewhat related to the bootloader and the order of the start-up time of the sensors. It's being actively looked into so I suspect we will have a solution shortly.

Whether that means a new ArduCopter/ArduPlane release or a 328 firmware upgrade remains to be seen!

Issue 411 has been merged into this issue.

This has been fixed in trunk and in 2.5.5-beta that is in the downloads area. IT should go out in the next patch release which should be very soon! Maybe today.

I have simulare problem. APM2 factory assembled bard. closest description is from the Troubleshooting guide: The APM board works when it's plugged into the USB, but not when it's powered by the RC rail (ESC/Lipo).

If I connect OSD-mavlink, the board red lights start flashing when powerd by lipo. If I start board without OSD-mavlink, the red light never start flashing. When I use Usb, it newer fails..

I've got the same problem and everything was updated today. When I boot from my lipo the blue led flashes then the yellow barely comes on and then they are both dead. I can get it to arm if I hook the lipo up and the usb then disconnect the usb. I just hope I don't have problems in the air.

@taylor,haugsvaer,

Although on the surface it sounds a bit similar to your issue, my guess is that this is a different issue.  Not 100% sure but your issues sound more like a power problems, possibly caused by mistakes in the wiring?

You need to provide 5v of power from a BEC or ESC into the input rail of the APM2 to provide power to the main CPU and miniOSD (if you've got one).  Plugging the ESCs into the output rail will not provide power to the main CPU..perhaps this sounds strange but the reason it's done this way is that for some configurations (planes and helicopters) they don't use ESCs but rather servos and we need to separate the power provided to the servos from the power provided to the CPU to avoid interferece.

@Taylor, is it possible you're plugging power from the ESC into the side of the APM instead of into the input pins? the power input lines on the side of the APM go through a voltage regulator..that regulator eats 1 volt or so you may be getting a brown out. I'm not totally sure, but that's my guess.

I'm going to close this issue but please feel free to raise a discussion on the main forums. you can also PM me to point me at your discussion in case i miss it.

Hope this helps.