Can't control rov2 servo by using MAV_CMD_DO_SET_SERVO

Blue Robotics Software ArduSub
1

I’m a Rookie in coding,and i have project which using QT create a UI to control my rov2.below is my code in qt creator.

mavlink_message_t msg;    
       uint8_t buf[MAVLINK_MAX_PACKET_LEN];

        //test servo
            mavlink_msg_command_long_pack(255,           // System ID
                                          1,        // Component ID
                                          &msg,           // MAVLink message
                                          0,                  // Target system ID
                                          0,                  // Target component ID
                                          MAV_CMD_DO_SET_SERVO, // Command ID
                                          0,                  // Confirmation
                                          2,
                                          1700, 0, 0, 0, 0,0);     // Parameters
                    qint64 len2 =mavlink_msg_to_send_buffer((uint8_t*)buf,&msg);
                     m_udpsend->writeDatagram((const char*)buf,QHostAddress("192.168.2.1"),14550);

I can recieve rov message(like heartbeat) from udp connection,but when sending these codes,rov have no reflect.
by the way I qdebug “(const char*)buf” in outpout,it is “0x74ca19”,is normal and corret?
thank u.

2

Hi @Baltard, welcome to the forum :slight_smile:

A couple of things that might help:

  1. The vehicle generally has both system ID and target ID as 1, not 0.
  2. 192.168.2.1 is the IP address of the topside computer - if that’s supposed to be the vehicle IP then it should (generally) be 192.168.2.2
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3

@EliotBR Thanks for the prompt response！I have tried your advice，the vehicle system ID and target
ID are both 1,and I changed the IP adress to 192.168.2.2,but it doesn’t seem to work :disappointed_relieved:.I read a pymavlink code,before I control the servo maybe I should change the MAV_MODE?Another question is should I send heartbeat message to the rov2 Regularly,is necessary for just test a servo?I feel a little confuse about the progress.Looking forward to your response.

4

I’ve just taken another look at this and it seems like you’re trying to set the PWM of servo 2, which is pretty much always assigned as a motor for use in controlling the vehicle (which generally need to be controlled with MANUAL_CONTROL or RC_CHANNELS_OVERRIDE messages, while the vehicle is armed).

If you want to use the DO_SET_SERVO command you’ll need to ensure the SERVOn_FUNCTION parameter (where n is the servo you’re trying to control) is set to Disabled (-1). This is not recommended for motion control outputs, so normally you would only do this for outputs 7+ in a standard BlueROV2, or 9+ if you’re using the heavy configuration.

If you’re using a Pixhawk note that servos 1-8 are MAIN 1-8, and servos 9-14 are AUX 1-6.

5

Thank you,Eliot!Today, I suecessfully control my rov. :clap:

1 Like