Unable to control servo using MAVSDK - set_actuator, MAV_CMD_DO_SET_ACTUATOR, MAV_CMD_DO_SET_SERVO not working

MAVSDK
1

Hi everyone,

I’m trying to control a servo(for payload drop) connected to MAIN OUT 1(for testing purpose i have connected to that port) on a Cube Orange+ using MAVSDK C++.

i am using px4 v1.15.4.

I’ve tried the following methods, but none of them seem to move the servo:

  1. Action::set_actuator()

  2. Sending MAV_CMD_DO_SET_ACTUATOR (command 187) via MavlinkPassthrough

  3. Sending MAV_CMD_DO_SET_SERVO (command 183) via MavlinkPassthrough

    even MAV_CMD_DO_MOTOR_TEST is also not working.

    mavlink_message_t msg;
    mavlink_msg_command_long_pack(
        passthrough->get_our_sysid(),
        passthrough->get_our_compid(),
        &msg,
        passthrough->get_target_sysid(),
        passthrough->get_target_compid(),
        MAV_CMD_DO_SET_ACTUATOR,
        0,                // Confirmation
        -1,    // param1 = servo number
        NAN,        // param2 = PWM value
        NAN, NAN, NAN, NAN, 0    // unused params
    );

    passthrough->send_message(msg);

    mavlink_command_long_t cmd{};
    cmd.target_system    = passthrough->get_target_sysid();
    cmd.target_component = passthrough->get_target_compid();
    cmd.command          = MAV_CMD_DO_SET_SERVO;
    cmd.confirmation     = 0;

    // actuator 9 (AUX OUT 1)
    cmd.param1 = 0;
    cmd.param2 = 1;
    // cmd.param3 = NAN;  // your desired position
    // cmd.param4 = NAN;
    // cmd.param5 = NAN;
    // cmd.param6 = NAN;
    // cmd.param7 = 0;            // block index

    mavlink_message_t msg{};
    mavlink_msg_command_long_encode(
        passthrough->get_our_sysid(),
        passthrough->get_our_compid(),
        &msg,
        &cmd
    );

    passthrough->send_message(msg);

action.set_Actuator(1,1.0);

above codes are not working.
PX4 console also shows warnings like:
[Warn] Received ack for not-existing command: 187! Ignoring...
I can confirm that the hardware and servo output work fine — the servo moves when using QGroundControl → Actuator Test.

Am i missing or doing anything wrong about it? Has anyone successfully controlled servos through MAVSDK on PX4?

Thanks in advance.