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40 lines
2.1 KiB
Markdown
40 lines
2.1 KiB
Markdown
# Firmware overview
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The firmware is a regular Arduino sketch, and 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 multiple files, each responsible for a specific part of the system.
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## Dataflow
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<img src="img/dataflow.svg" width=800 alt="Firmware dataflow diagram">
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The main loop is running at 1000 Hz. All the dataflow is happening through global variables (for simplicity):
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* `t` *(double)* — 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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* `controls` *(float[])* — user control inputs from the RC, normalized to [-1, 1] range.
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* `motors` *(float[])* — motor outputs, normalized to [-1, 1] range; reverse rotation is possible.
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## Source files
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Firmware source files are located in `flix` directory. The key files are:
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* [`flix.ino`](../flix/flix.ino) — main entry point, Arduino sketch. Includes global variables definition 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) — drone's attitude estimation, complementary filter.
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* [`control.ino`](../flix/control.ino) — drone's attitude and rates control, three-dimensional two-level cascade PID controller.
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* [`motors.ino`](../flix/motors.ino) — PWM motor outputs control.
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Utility files include:
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* [`vector.h`](../flix/vector.h), [`quaternion.h`](../flix/quaternion.h) — project's vector and quaternion libraries implementation.
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* [`pid.h`](../flix/pid.h) — generic PID controller implementation.
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* [`lpf.h`](../flix/lpf.h) — generic low-pass filter implementation.
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## Building
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See build instructions in [build.md](build.md).
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