APM2.5 NO GREEN BARS from RC input

I recently purchased my first autonomous aircraft from 3DRobotics, so I'm fairly new to all of this.  I got the ArduCopter kit with the APM2.5 and right now I'm stuck at the point where I need to calibrate the RC inputs in the Mission Planner.  I did my best to research this problem but so far nothing has worked.  Thanks in advance for your help!!  Even a link to point me in the right direction would be terrific!

Here's my setup:

The APM2.5 is connected to the computer via USB.  The signal wires from a Spektrum AR7000 receiver are connected to the corresponding inputs of the APM.  I have tried everything below with the GPS (uBlox LEA-6), 3DR radio, and Power Module both connected and disconnected.

The receiver is powered by one of the input channels on the APM (via the supplied 2-wire female-female cable).  I did this based on the first sentence of this link which says

For the APM 2 this setup can be performed without connecting a battery. (Generally the USB port will provide sufficient power for both the APM 2 board and the receiver.)

Here's what I've tried:

I read the troubleshooting guide here, but the first line of step 1 says

The USB cable will NOT power the RC receiver.

So which is right?  I'm assuming this last statement was intended for the APM1 but can anyone verify that?

Step 5 of the troubleshooting guide mentions there have been problems with some Spektrum receivers and describes how to bind with it.  However I had no issue binding and was able to control a servo on the rudder channel.  Taking advice from step 8, I then plugged only the rudder signal into the rudder input on the APM but still no green bar anywhere on the "Radio Calibration" screen (still connected to the Mission Planner).

Then I looked at the PWM rudder signal on my oscilloscope and the width of the pulse widened and narrowed as I moved the rudder stick back and forth, just as expected.  But I also noticed that each pulse had a magnitude of only 4V.  I was expecting to see 5V since that's what the receiver was getting from the APM, but I don't know, maybe this is normal.  Also the period between each pulse was 22ms for a frequency of 45.45Hz - but again I don't know if this is normal or not.  Does anyone know if these values are right or better yet where I can find the expected specs for input PWM signals?

I'm now at the point where I'd like to try to power the receiver independent of the APM.  But after looking at the power schematic of the APM2.5 (here) I'm worried about the voltage mismatch between what's supplied by the USB cable (which is made available on the 5V pin of the PWM inputs) and the the 5V line coming from receiver.  Though, I suppose I don't need to send over the 5V line from the receiver to the APM (since I'm still using USB) but I do need to connect the GNDs so they'll be common...  Does this seem like a good idea or is there something better to try? 

As I said above I'm pretty new to this so I'm wondering if I need to do something like reformat or clear the APM2.5.  Last night I updated the mission planner and downloaded the newest Quadrotor software to the APM2.5 but still no success.  Sorry for the long post!  I just want to be clear to avoid confusion.    

Thanks for your help!!

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  • The APM2.5 was repaired by 3DR and now It's working perfectly! They said it was likely that the on-board power regulator needed to be replaced.  It took a total of about 4 weeks to get it repaired (to get the RMA number, ship it back, for it to be repaired, and finally shipped back) which is about 2 weeks too long for me but that said they were very friendly and helpful along the way and it didn't cost me a dime (they gave me store credit for the cost of shipping it back).  My understanding is they're currently ramping up employment so I suspect the wait time for emails and repairs will only decrease.  

    If you're having this same problem I'd suggest you contact 3DR through email so you can have it sent back and repaired so you can get back in the air!

  • I am having the same exact problem...


    I just received my APM2.5 but I need some help with troubleshooting.

    I have read the forums and checked almost everything but I am uable to calibrate the radio using mission planner.


    First, the configuration:

    • Receiver connected to input channels 1-4
    • Servos connected to output channels 1-4
    • All flight hardware (Receivers and Servos) are flight proven and function flawlessly without APM.
    • Receiver battery connected to output rail to provide servo power for test purposes
    • uBloc GPS connected and locked
    • Current revision mission planner and firmware
    • Windows 7
    • APM 2.5 connected to USB on computer

    Second the problem:

    • I verify I am connected and mission planner goes through the configuration parameters.
    • I attempt to calibrate Radio with Misson Planner (Press calibrate button) and the bars remain gray.
    • Axes bars remain grey throughout joystick motion.
    • When I close the calibration there are no valid PWM readings displayed. (0)
    • I can see PWM input with oscilloscope on all 4 channels.  The PWM changes when I move sticks.
    • I can calibrate the radio successfully using CLI with reasonable PWM readings.
    • I can calibrate compass and set declination using CLI.
    • The servos move when I move joysticks.
    • I can communicate, set and read configuration, including GPS, compass, and transmitter joystick PWM positions, from CLI.
    • The HUD does not show any data.

    Here is what I have tried:

    • Both Airplane and Hexcopter firmware downloaded through mission planner.
    • Two different receivers (Spektrum RM8000 2.4Ghz DSMX and Futaba 72Mhz receiver).
    • Two different transmitters (Spektrum DX8 and Futaba 6EXP)
    • Different cables between reciever and APM.
    • Different USB cable.
    • Different USB connectors.
    • Rebooting computer.
    • Second computer (Windows XP).
    • No servos
    • No battery on output

    I just don't know what to try next.  


    This looks like it might be a common problem based on forums but no one seems to know how to fix it.

    Because the hardware seems to be working through the command line interface and control the servos I suspect this is a Mission Planner problem.

  • 3D Robotics

    Thanks for the catch on an outdated (APM 1) mention; I've updated that page. 

    Did you click on the Calibrate Radio button? It often won't show the bars until you do that. 

  • Actually I think the problem is with the Mission Planner software and not the APM2.5.  I say this because I can see the raw data from the remote in the terminal window (using the "test" -> "radio" CLI commands) and the values change with the stick movements on the remote.  But when I switch over to the 'Radio Calibration' window there are no green bars... weird. Is this a known issue with MP?

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