Grading Criteria

• 20 (/ 100) points: simulation code and verbal discussion
  • 14 points code (written core math routines; correct dynamics; infrastructure code for simulation)
  • 3 points integration schema analysis
  • 3 points validation analysis

Assignment 1

1. Show an example run of your code.
2. Show your table/plot/results comparing two integration schemes.
3. Show your validation of the dynamics.

• What was difficult?
• What was easy?

Notes and Lessons Learned

• Please use f32, not f64 (the real hardware has a single-precision FPU)
• Avoid committing/pushing temporary files (e.g., target folder; use .gitignore)

Crazyflie 2.1 Hardware Overview

Crazyflie 2.1 Hardware Schema

Crazyflie 2.1 Notable Extensions

Crazyradio

Crazyflie 2.1 Official Software

• User facing libraries
  1. Phone applications (Android, iPhone)
  2. cflib: Python API to control robot(s) via Crazyradio
  3. cfclient: GUI for a single robot (Python, based on cflib)
• Low-level (mostly C)
  1. STM32 Firmware: Primary flight control firmware
  2. AI deck examples
  3. NRF51 firmware, various Bootloaders, Crazyradio firmware

Flight Demo

• Crazyflie with flow deck controlled in cfclient

Flight Control Firmware (CF)

• Hardware Abstraction Layer (HAL)
• Stabilizer loop, state estimation, controller, commander / planner

Flight Control Firmware (PX4)

• state estimation
• controller

Flight Control Demo: Hello Rust

Install Rust for our target:

rustup target add thumbv7em-none-eabihf

Build official example:

git clone git@github.com:bitcraze/crazyflie-firmware.git
cd crazyflie-firmware
git submodule update --init
cd examples/app_hello_rs
make clean
make

Flash:

1. Turn of the Crazyflie (short press power button)
2. Put in bootloader (press power button for about 3 seconds)
3. make cload

Flight Control Demo: Custom Controller

cd ../app_out_of_tree_controller
make clean
make

Background

• Projects are often written in several different languages

How can we cross the language barrier?

Calling Rust From C

• Mark as extern C and disable name mangling

Export a function written in Rust

#[no_mangle]
pub extern "C" fn hello_from_rust() {
    println!("Hello from Rust!");
}

Call the function from C

extern void hello_from_rust();

int main(void) {
    hello_from_rust();
    return 0;
}

Calling C From Rust

• Import a function (need to use Rust syntax and types!)

C function to import

int consolePutchar(int ch);

Rust code to call that function

extern "C" {
    pub fn consolePutchar(ch: i32) -> i32;
}

fn main() {
    consolePutchar(82);
}

Revisiting app_hello_rs

#![no_std]

use panic_halt as _;

extern "C" {
    pub fn vTaskDelay(ticks: u32);
    pub fn consolePutchar(ch: i32) -> i32;
}

fn console_print(msg: &str) {
    for c in msg.as_bytes() {
        unsafe{ consolePutchar(*c as i32); }
    }
}

#[no_mangle]
pub extern "C" fn appMain() -> i32 {
    console_print("Hello from Rust2!\n");

    loop {
        unsafe { vTaskDelay(1000); }
    }
}

Practical Considerations and Other Languages

• More details: see Foreign Function Interface
• Converting C(++) syntax to Rust can be hard for custom data types (nested structs, unions, …)
  • use bindgen instead
• Python ⇔ Rust: pyo3

Instructions

1. Make sure you can compile the firmware (instructions)
2. Create your own “app” example for assignment1
3. Add and compile your existing math library
   • Trigonometric functions are not in core; import sinf, cosf etc. from C
4. Generate bindings for the controller using bindgen
   • The easiest (to not deal with errors) is to copy stabilizer_types.h and only include the structs that you need
5. Test flight with stock software
   • Tuesday 12:30 - 14:00, or
   • Thursday 13:00 - 14:00
   • Schedule a timeslot online

Learned Today

• Assignment 1 grading
• Specifics of the hard- and software used for the class
• Rust: Interoperability with other languages
• Assignment 1.5 (as preparation for assignment 2)

Questions