Unable to arm sitl px4 using mavros (works in QGC)

[jojo-le-pirate]

Hi everyone!
I am running px4 in sitl mode in a virtualbox environment, hooked up with jMAVSim.
Mavros is running correctly, receives the heartbeats from the simulated px4.
QGC is even connected to px4 using mavros' proxy port.
QGC works correctly, i can arm the px4 or do whatever I want.
When trying to arm the px4 with mavros by running:
rosrun mavros mavsafety arm
I get the error
Request failed. Check mavros logs
If I try
rosservice call /mavros/cmd/arming "value: true"
I get success: false result 4

Nothing happens in the px4 terminal when those commands are issued.
I am using the latest git version of everything.

mavros is launched using roslaunch mavros px4.launch

I have exactly the same problem as in #283 except I am running a simulated px4 (software in the loop).

Thank you for your help!

rostopic echo -n1 /diagnostics` yields:

`header: 
  seq: 371
  stamp: 
    secs: 1445527373
    nsecs: 260117542
  frame_id: ''
status: 
  - 
    level: 0
    name: mavros: FCU connection
    message: connected
    hardware_id: udp://:14556@192.168.0.10:14556
    values: 
      - 
        key: Received packets:
        value: 3446
      - 
        key: Dropped packets:
        value: 0
      - 
        key: Buffer overruns:
        value: 0
      - 
        key: Parse errors:
        value: 0
      - 
        key: Rx sequence number:
        value: 11
      - 
        key: Tx sequence number:
        value: 42
      - 
        key: Rx total bytes:
        value: 12615499
      - 
        key: Tx total bytes:
        value: 12615523
      - 
        key: Rx speed:
        value: 32478.000000
      - 
        key: Tx speed:
        value: 32502.000000
  - 
    level: 0
    name: mavros: GCS bridge
    message: connected
    hardware_id: udp://:14556@192.168.0.10:14556
    values: 
      - 
        key: Received packets:
        value: 3446
      - 
        key: Dropped packets:
        value: 0
      - 
        key: Buffer overruns:
        value: 0
      - 
        key: Parse errors:
        value: 0
      - 
        key: Rx sequence number:
        value: 11
      - 
        key: Tx sequence number:
        value: 0
      - 
        key: Rx total bytes:
        value: 12615470
      - 
        key: Tx total bytes:
        value: 12615470
      - 
        key: Rx speed:
        value: 32478.000000
      - 
        key: Tx speed:
        value: 32478.000000
  - 
    level: 2
    name: mavros: GPS
    message: No satellites
    hardware_id: udp://:14556@192.168.0.10:14556
    values: 
      - 
        key: Satellites visible
        value: 0
      - 
        key: Fix type
        value: 0
      - 
        key: EPH (m)
        value: Unknown
      - 
        key: EPV (m)
        value: Unknown
  - 
    level: 0
    name: mavros: Heartbeat
    message: Normal
    hardware_id: udp://:14556@192.168.0.10:14556
    values: 
      - 
        key: Heartbeats since startup
        value: 4756
      - 
        key: Frequency (Hz)
        value: 8.928667
      - 
        key: Vehicle type
        value: Onboard-Controller
      - 
        key: Autopilot type
        value: INVALID
      - 
        key: Mode
        value: CMODE(0)
      - 
        key: System status
        value: Active
  - 
    level: 0
    name: mavros: System
    message: Normal
    hardware_id: udp://:14556@192.168.0.10:14556
    values: 
      - 
        key: Sensor present
        value: 0x00000000
      - 
        key: Sensor enabled
        value: 0x00000000
      - 
        key: Sensor helth
        value: 0x00000000
      - 
        key: CPU Load (%)
        value: 0.0
      - 
        key: Drop rate (%)
        value: 0.0
      - 
        key: Errors comm
        value: 0
      - 
        key: Errors count #1
        value: 0
      - 
        key: Errors count #2
        value: 0
      - 
        key: Errors count #3
        value: 0
      - 
        key: Errors count #4
        value: 0
  - 
    level: 2
    name: mavros: Battery
    message: No data
    hardware_id: udp://:14556@192.168.0.10:14556
    values: 
      - 
        key: Voltage
        value: -1.00
      - 
        key: Current
        value: 0.0
      - 
        key: Remaining
        value: 0.0
  - 
    level: 2
    name: mavros: Time Sync
    message: No events recorded.
    hardware_id: udp://:14556@192.168.0.10:14556
    values: 
      - 
        key: Timesyncs since startup
        value: 0
      - 
        key: Frequency (Hz)
        value: 0.000000
      - 
        key: Last dt (ms)
        value: 5.549022
      - 
        key: Mean dt (ms)
        value: 0.000000
      - 
        key: Last system time (s)
        value: 1445527110.060583830
      - 
        key: Time offset (s)
        value: 237.567260241

---

[vooon]

Please check console output from px4.launch (mavros log).
Usually when arm is failing there some messages FCU: which describe problem (coming from autopilot).
Especially look at prearm messages.