Rover Code Configuration

Load the code:

If you have not already done so, download and install the Mission Planner.Mac and Linux users can use APM Planner This manual will use Mission Planner as the reference, however.

Once you have installed Mission Planner, run it. Use your USB cable to plug the APM 2.5 into your PC. In the Mission Planner (top right of window), select the COM port that Windows assigned to your APM 2.5 and ensure that the baud rate is 115200. Once that is done, you can load the Rover firmware on to APM 2.5. Just click on the icon shown belpw in the Firmware tab. The code will automatically load.


Once the code is loaded, press the “Connect” button in the top right of the Mission Planner, and it should connect to the APM 2.5 board via MAVLink. After that is done, you can switch to the Configuration tab and do the setup as follows.

Calibrate Your RC settings:

With APM 2.5 connected via USB and the RC connected as per the hardware installation instructions, turn on your RC transmitter. If your RC receiver (Rx) and transmitter (Tx) are bound, you should be able to see the green pars in the Radio Calibration section moving when you move the transmitter sticks.

If they are not moving, check:

  • Is the solid green light on your receiver? If it’s red or flashing green, your RC transmitter isn’t on or your Rx/Tx need be bound (see the manual that came with your RC equipment for how to do that)
  • If there is no light at all on your receiver, check that you wired it correctly to APM 2.5 (look for connectors that may have been inserted upside down)
  • If you have a solid green light on the receiver and APM 2.5 is connected to the Mission Planner but the bars are still not moving, try clicking on the “Calibrate Radio” button.


If the green bars do move when you move the sticks, click on the “Calibrate Radio” button. After you click OK on some warning dialogs, red lines will appear on the green bars. Move the sticks (you only need to do the ones for the channels you have connected to APM) until you have pushed the red lines as far as they will go in all direction, as shown below:


  • For reverse steering in MANUAL mode, reverse the direction of that channel on your transmitter.
  • For reverse steering in AUTO mode, check the “Reverse” checkbox for the ROLL channel in the Mission Planner as shown above

Assign Modes:

Now switch to the Flight Modes section. This is where we will tell APM what modes to assign to each position of your Channel 5 toggle switch. Most toggles switches can only handle two or three positions, but there are ways to combine channels to get six or more. That isn’t normally needed for Rover, but if you want to learn more about having more than three modes, see the instructions (Here!).


  • Typically, your transmitter’s three-way toggle switch will be on Channel 5 and your two-way momentary toggle will be on Channel 7. If this is not the case, you can change that with your RC transmitter menus (see your RC manual for details).
  • When you move the Channel 5 toggle, the green bar shown above will move to different modes. You can assign the function of those modes with the drop-down menu next to each.

The modes are described in Rover Control Modes.

Calibrate the compass

This step is important. Rover does most of its steering based on the compass, and if that sensor is giving bad results, either because it wasn’t calibrated right or if it’s seeing too much magnetic interference, the rover will wander all over the place.


Now go to the Hardware Options section and ensure that the Compass Enable and Auto Dec checkboxes are set. Then click on the Live Calibration button and, holding the rover in the air (as far from metal desks, cars or other sources of magnetic interference as possible) rotate it in all directions (360 degrees) on all three axes (pitch, roll, yaw) for about a minute to collect enough data to calibrate the compass. A dialog box will pop up when it has all the data it needs and will tell you the offset value. If that value is less than around 150, you should be fine. If it’s higher than that, try the calibration again.

Note: It’s often better to do this test with the car’s motor running, to ensure that any magnetic interference from the motor is included in the compass calibration.

Next Step: Plan a Mission

Set up some Parameters

  • Connect to Mission Planner via the USB cable and select “Connected”  and go to the Config/Tuning tab.
  • Select the Planner item in the left menu and ensure the Advanced View item on the bottom right is checked.
  • Click on the Standard Params item in the left menu and install some conservative starting parameters.
    • Set the Channel 7 Option to Learn Waypoint if it is not already set to it.
    • Reduce Target cruise speed in auto from 5.00 to 2.50.
    • Reduce Base throttle percentage from 50 to 30.
  • Set a failsafe to turn your vehicle off (put it in HOLD mode) if you lose RC reception for 5 seconds.
    • Set Failsafe Action to HOLD.
    • Set GCS failsafe enable to Disabled unless you are using a 3DR Telemetry radio.
    • Set Throttle Failsafe Enable to Enabled
    • Failsafe is preset to 5 seconds but can be adjusted in the Full Parameter List with the FS_TIMEOUT parameter.
  •  Select the Advanced Params item from the left menu and ensure the Board Orientation Item matches your setup.
    • I mount my PX4 upside down for improved connector access so I set this to Roll 180 (8).
    • If your controller is mounted right side up select None.
  • Scroll down to Compass Orientation and ensure it is set correctly for your compass.
    • This should have been set in Compass Calibration section above.
  • Scroll down to RC trim PWM (RC3_TRIM) and set it up for (reverse – center – forward) throttle or not.
    • Throttle is normally channel 3, if you have changed it to another channel go there instead.
    • If you have a center loaded throttle with reverse, set this value to 1500, if not leave it at 1100.
  • I also set my transmitter so throttle (channel 3) is moved to the right center loaded elevator stick.
    • And steering (channel 1) is moved to the left rudder stick.
    • You need an appropriately programmable transmitter to do this.
    • Otherwise you can reassign the RC channels in the Flight Controllers Advanced Parameter List instead.
    • You will need to steer with the left stick and go forward and reverse with the right stick, but it is easy with a little practice.

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