6.1.2 Configuration
- Jacopo Tani
All FC configuration pages are important, but misconfiguring the motors might yield catastrophic results (e.g., undesirable flips).
Read and follow the instructions on this page with particular attention.
Mixer: This setting tells the FC what is the shape of the drone. The shape of the drone and the direction of spinning of the motors (clockwise or counter-clockwise) are necessary for the FC’s internal "motor mixing algorithm" that maps higher-level commands (i.e., roll, pitch, yaw, and thrust), which make sense to humans, to lower level commands (“speeds” of each motor:
m1, …,m4), which make more sense to the drone.
The correct setting for the
DD21is "Quad X";We will later (https://ethidsc.atlassian.net/l/cp/xi5QGdfp) verify that each motor is spinning in the right direction.
Do not reverse the direction of the motors.
Take note of the motor numbering with respect to the “front” of the drone, i.e., where the red arrow is pointing. We will define the DD21 front as where the camera is, and place Captain duckie facing in that direction to remind us of it all the time.
Board and sensor alignment
The FC has an internal IMU, providing linear acceleration and angular rate measurements, with respect to the FC principal axes (ux, uy, uz). The principal axes of the FC, according to the measurements of linear and angular accelerations provided by the IMU, are as follows:
uxis positive in the direction identified by the arrow serigraph on the PCB;uzis orthogonal to the plane identified by the FC’s PCB, and positive "coming out of the screen";uyis such that (ux,uy,uz) is a right-handed reference system.
Depending on how the FC is physically mounted on the DD21 (e.g., upside down, at an angle, sideways, etc.), angles can be “compensated” to make the drone body frame match this assumption.
If you have followed the hardware assembly instructions provided and mounted the FC under the drone, with the small arrow on it pointing towards the camera, the correct settings are the following:
Accelerometer Trim
Leave it with default values of 0 and 0.
Arming
This is a safety feature that prevents the drone from arming, hence spinning the motors, if the measured roll or pitch is above the indicated value. In other words, this field should be a small number, e.g., 5 (degrees), so to prevent the drone from accidentally arming while not on a flat surface (e.g., when you are carrying it around in your hands).
System configuration
Select values as below. Note that the PID loop frequency is capped at 0.5 kHz by the PWM ESC/Motor protocol.
Receiver
Select the MSP RX input option.
ESC/Motor Features
The most important item to change is the “Minimum Throttle” setting: bring it up to 1100.
Other features
Enable “telemetry” to receive data from the FC to feed to our autonomy stack. Disable other options.