connected with a real drone problem

[wangpuxia]

hi

I set up a mavsdk environment on the server and tested it using jmavsim. Everything work fine
But when I connected the real drone to Mavsdk, Some functions can be used normally, such as

System drone = new System ( "123.201.28.156" , 50041 ) ;
drone.getTelemetry().getFlightMode().subscribe(flightMode -> logger.info("Flight mode: " + flightMode));

It can return the flightmode data correctly, but most functions such as

drone.getAction ( ).arm ( ) or
drone.getTelemetry ( ).getBattery ( )

do not provide any feedback. The server will output content similar to the following:

[09:49:05|Info ] MAVSDK version: v2.11.0 (mavsdk_impl.cpp:26)
[09:49:05|Info ] Waiting to discover system on udp://:14552... (connection_initiator.h:20)
[09:50:20|Info ] New system on: 39.144.112.2:48334 (with system ID: 1) (udp_connection.cpp:199)
[09:50:20|Debug] New system ID: 1 Comp ID: 1 (mavsdk_impl.cpp:720)
[09:50:20|Debug] Component Autopilot (1) added. (system_impl.cpp:366)
[09:50:20|Warn ] Vehicle type changed (new type: 2, old type: 0) (system_impl.cpp:217)
[09:50:20|Debug] Discovered 1 component(s) (system_impl.cpp:509)
[09:50:20|Info ] System discovered (connection_initiator.h:62)
[09:50:20|Info ] Server started (grpc_server.cpp:169)
[09:50:20|Info ] Server set to listen on 0.0.0.0:50042 (grpc_server.cpp:170)
[09:50:21|Debug] MAVLink: critical: PreArm: Throttle below Failsafe (system_impl.cpp:243)
[09:50:21|Debug] MAVLink: critical: PreArm: Hardware safety switch (system_impl.cpp:243)
[09:50:22|Debug] MAVLink: info: u-blox 1 HW: 00080000 SW: EXT CORE 3.01 (107900) (system_impl.cpp:243)
[09:50:51|Debug] MAVLink: critical: PreArm: Throttle below Failsafe (system_impl.cpp:243)
[09:50:51|Debug] MAVLink: critical: PreArm: Hardware safety switch (system_impl.cpp:243)
[09:51:17|Warn ] sending again after 0.502024 s, retries to do: 3 (512). (mavlink_command_sender.cpp:320)
[09:51:17|Warn ] Request was for msg ID: 242 (mavlink_command_sender.cpp:326)
[09:51:18|Warn ] sending again, retries to do: 5 (mavlink_parameter_client.cpp:1057)
[09:51:21|Debug] MAVLink: critical: PreArm: Throttle below Failsafe (system_impl.cpp:243)
[09:51:21|Debug] MAVLink: critical: PreArm: Hardware safety switch (system_impl.cpp:243)
[09:51:51|Debug] MAVLink: critical: PreArm: Throttle below Failsafe (system_impl.cpp:243)
[09:51:51|Debug] MAVLink: critical: PreArm: Hardware safety switch (system_impl.cpp:243)
[09:52:13|Warn ] sending again after 0.501734 s, retries to do: 3 (512). (mavlink_command_sender.cpp:320)
[09:52:13|Warn ] Request was for msg ID: 242 (mavlink_command_sender.cpp:326)
[09:52:21|Warn ] sending again after 0.51101 s, retries to do: 3 (512). (mavlink_command_sender.cpp:320)
[09:52:21|Warn ] Request was for msg ID: 242 (mavlink_command_sender.cpp:326)
[09:52:21|Debug] MAVLink: critical: PreArm: Throttle below Failsafe (system_impl.cpp:243)
[09:52:21|Debug] MAVLink: critical: PreArm: Hardware safety switch (system_impl.cpp:243)
[09:52:50|Debug] MAVLink: critical: PreArm: Throttle below Failsafe (system_impl.cpp:243)
[09:52:50|Debug] MAVLink: critical: PreArm: Hardware safety switch (system_impl.cpp:243)
[09:53:20|Debug] MAVLink: critical: PreArm: Throttle below Failsafe (system_impl.cpp:243)
[09:53:20|Debug] MAVLink: critical: PreArm: Hardware safety switch (system_impl.cpp:243)
[09:53:50|Debug] MAVLink: critical: PreArm: Throttle below Failsafe (system_impl.cpp:243)
[09:53:50|Debug] MAVLink: critical: PreArm: Hardware safety switch (system_impl.cpp:243)
[09:54:20|Debug] MAVLink: critical: PreArm: Throttle below Failsafe (system_impl.cpp:243)
[09:54:20|Debug] MAVLink: critical: PreArm: Hardware safety switch (system_impl.cpp:243)

May I ask where the problem occurred? and how to fix it.

[JonasVautherin]

[09:50:21|Debug] MAVLink: critical: PreArm: Throttle below Failsafe (system_impl.cpp:243)
[09:50:21|Debug] MAVLink: critical: PreArm: Hardware safety switch (system_impl.cpp:243)

This suggests that the arm command reaches the autopilot, and the autopilot refuses to arm (because of the throttle). Are you sure that MAVSDK doesn't return an error there? How do you actually call it (drone.getAction().arm() won't call it, you have to subscribe at some point).

For the telemetry, are you sure that your drone is sending those updates? E.g. does QGC receive them?

[julianoes]

Duplicate of mavlink/MAVSDK-Java#174