TeensyFlight36: A C++ repository from dakejahl

What's the point?

Aiming to improve in embedded firmware, electrical engineering, and software design. https://hackaday.io/project/167420-teensyflight36

Features

Makefile + SWD GDB upload and debug
FreeRTOS
BSP is essentially cores/teensy3
Dispatch queue for asynchronous and interval scheduling (100us tick interrupt)
Publish / subscribe communication framework
MPU9250 @ 1kHz gyro / accel / mag on 10MHz SPI
FrSky XM+ mini on UART SBUS
400Hz PWM outputs for actuator control signals
250Hz attitude estimation, 1kHz control. Complimentary filter attitude estimator using euler angles, [WIP] quaternion estimator w/ EKF
Data streaming in csv format over serial
Interactive plotting and visualizations with python and OpenGL

Things I'd like to do...

Telemetry radio to host
MAVLink over telemetry radio for QGC communication
Full quaternion estimation and control
Optical flow for position hold

Tools

make / CMake
GDB
MCUXpresso
JLink mini
Siglent SDS1202X-E

Components

Teensy 3.6 microcontroller board
MPU9250 3-axis gyro / accel / mag
FrSky Mini radio transmitter
Blade Theory XL kit from amazon. Removed camera, radios, and flight controller board (leave the power distribution board attached).
Lipow battery charger
TaranisQ X7 remote controller

Building with make

I started with a framework I had been hearing about called platformio. I figured it sounded cool and I'd try it out. It became severely limiting as soon as I wanted to do anything more than what was supported from it natively, so I switched to a makefile. Using a hodgepodge of references from the interwebs, I created a makefile based build system that can be easily invoked via the command line or from an IDE.

SWD Debugging: JLink + GDB

Now this is a hardware hack. I soldered the reset line on the companion microcontroller (KL02) to ground, this holds the KL02 in reset and thus prevents its activity on the SWD lines. https://mcuoneclipse.com/2017/04/29/modifying-the-teensy-3-5-and-3-6-for-arm-swd-debugging/

Thread aware debug with MCUXpresso

I nice tool built into MCUXpresso, only requiring a somewhat poorly explained process for configuring it. I was able to piece it together from scouring the internet, and it is really useful! You can view your stack sizes, heap usage, and % cpu at any breakpoint.

Segger SystemView

An amazing tool if you really want to take a detailed look "inside" of your machine. You can instrument any section of code you'd like using the API, however I chose to only verify ISR / Task interaction and timing characteristics.
https://www.segger.com/products/development-tools/systemview/

Attitude visualization

I created a tool using OpenGL to visualize attitude data coming from the flight controller in real time.

Data visualization

I created a tool in C++ that reads 3-axis data from the serial port and optionally writes it to a file. I then run an ellipsoid fit algorithm on the data set and plot the data in 3D with the caclulated offsets and scales for each axis. https://plot.ly/python/3d-scatter-plots/

Live plotting

I use the 3-axis data stream and plot the results in real time. I can choose the data stream I am interested in with a simple shell command via the USB port.
i.e stream rpy data

Rate loop tuning

I started by tuning the pitch controller first, and then duplicated those settings for the roll controller. My flight controller is mostly symmetric so this worked well. I configured a data stream to send the setpoints and the measured pitch/roll/pitchrate/rollrate so that I could see the effects of changes to the controller gains.