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774144c430
Updates to main readme. Add much more info to usage article. Move simulator building to simulation's readme. Improve assembly article. Many fixes. Updates in diagrams.
68 lines
3.4 KiB
Markdown
68 lines
3.4 KiB
Markdown
# Firmware overview
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The firmware is a regular Arduino sketch, and it follows the classic Arduino one-threaded design. The initialization code is in the `setup()` function, and the main loop is in the `loop()` function. The sketch includes several files, each responsible for a specific subsystem.
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## Dataflow
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<img src="img/dataflow.svg" width=600 alt="Firmware dataflow diagram">
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The main loop is running at 1000 Hz. The dataflow goes through global variables, including:
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* `t` *(float)* — current step time, *s*.
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* `dt` *(float)* — time delta between the current and previous steps, *s*.
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* `gyro` *(Vector)* — data from the gyroscope, *rad/s*.
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* `acc` *(Vector)* — acceleration data from the accelerometer, *m/s<sup>2</sup>*.
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* `rates` *(Vector)* — filtered angular rates, *rad/s*.
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* `attitude` *(Quaternion)* — estimated attitude (orientation) of drone.
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* `controlRoll`, `controlPitch`, `controlYaw`, `controlThrottle`, `controlMode` *(float)* — pilot control inputs, range [-1, 1].
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* `motors` *(float[4])* — motor outputs, range [0, 1].
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## Source files
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Firmware source files are located in `flix` directory.
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* [`flix.ino`](../flix/flix.ino) — Arduino sketch main file, entry point.Includes some global variable definitions and the main loop.
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* [`imu.ino`](../flix/imu.ino) — reading data from the IMU sensor (gyroscope and accelerometer), IMU calibration.
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* [`rc.ino`](../flix/rc.ino) — reading data from the RC receiver, RC calibration.
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* [`estimate.ino`](../flix/estimate.ino) — attitude estimation, complementary filter.
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* [`control.ino`](../flix/control.ino) — control subsystem, three-dimensional two-level cascade PID controller.
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* [`motors.ino`](../flix/motors.ino) — PWM motor output control.
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* [`mavlink.ino`](../flix/mavlink.ino) — interaction with QGroundControl or [pyflix](../tools/pyflix) via MAVLink protocol.
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* [`cli.ino`](../flix/cli.ino) — serial and MAVLink console.
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Utility files:
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* [`vector.h`](../flix/vector.h), [`quaternion.h`](../flix/quaternion.h) — vector and quaternion libraries.
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* [`pid.h`](../flix/pid.h) — generic PID controller.
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* [`lpf.h`](../flix/lpf.h) — generic low-pass filter.
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### Control subsystem
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Pilot inputs are interpreted in `interpretControls()`, and then converted to the *control command*, which consists of the following:
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* `attitudeTarget` *(Quaternion)* — target attitude of the drone.
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* `ratesTarget` *(Vector)* — target angular rates, *rad/s*.
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* `ratesExtra` *(Vector)* — additional (feed-forward) angular rates , used for yaw rate control in STAB mode, *rad/s*.
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* `torqueTarget` *(Vector)* — target torque, range [-1, 1].
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* `thrustTarget` *(float)* — collective thrust target, range [0, 1].
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Control command is handled in `controlAttitude()`, `controlRates()`, `controlTorque()` functions. Each function may be skipped if the corresponding control target is set to `NAN`.
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<img src="img/control.svg" width=300 alt="Control subsystem diagram">
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Armed state is stored in `armed` variable, and current mode is stored in `mode` variable.
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### Console
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To write into the console, `print()` function is used. This function sends data both to the Serial console and to the MAVLink console (which can be accessed wirelessly in QGroundControl). The function supports formatting:
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```cpp
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print("Test value: %.2f\n", testValue);
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```
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In order to add a console command, modify the `doCommand()` function in `cli.ino` file.
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## Building the firmware
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See build instructions in [usage.md](usage.md).
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