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  FAURO: Flight Software

Section 1: Project Overview

Welcome to FAURO! This repository houses the Flight Software source code for an avionics platform that has a small form factor and can fit into an amateur rocket kit. While the focus of this project is the Flight Software for the avionics, you will also find source code for ground support equipment, design documentation, and log files from flights. It is a follow-on to the AURO project. While AURO was implemented in C using a custom-designed FSW architecture, FAURO will be implemented using the F' Flight Software Framework

Before going further, I would like to cover my motivation for this project so many of the architecture decisions make more sense. I am interested in developing a system that allows me to challenge and showcase my capabilities as a Flight Software Engineer. While the term Embedded Software Engineer is used more broadly across different industries, I am using the term Flight Software (FSW) throughout to signal that the expectation for autonomy and fault tolerance of this code should be on par with design principles used in spaceflight applications.

Section 1.1: Mission System Architecture

This project is made up of four distinct systems. When referred to all together, the term Mission System is used. At an individual system level, there is FAURO or the Flight System, the Launch Station, the Base Station, and the Ground System. Sometimes, the final three are jointly referred to as the Ground Segment.

  1. FAURO

    • The flight vehicle and where much of the development effort is focused. The 3D printed Avionics Bay that accompanies FAURO can fit into 76mm diameter rocket kits.
    • The hardware consists of:
      • 3.7v 500mAh Lithium Ion Polymer Battery
      • Flight Computer: ATSAMD21G18 ARM Cortex M0 processor
      • Micro SD storage flight logger
      • 915 MHz radio
      • Accelerometer
      • Magnetometer
      • Gyroscope
      • Altimeter
      • GPS receiver
    • Developed in C++ using the F' Flight Software Framework. While the aforementioned AURO project used the FreeRTOS kernel, the barmetal scheduler needed to be utilized for FAURO due to image size constraints.

      The integrated FAURO system
        

  2. The Base Station

    • A device that receives flight data from FAURO and passes it along a serial interface to the ground system
    • The hardware consists of:
      • ATSAMD21G18 ARM Cortex M0 processor
      • 915 MHz radio
    • Developed in C++

      The integrated Base Station


  3. The Ground System

    • For this project, the F' GDS that ships with F' will be used.

  4. The Launch Station

    • A device that energizes the launch circuit when commanded to ignite the rocket motor
    • Hardware consists of:
      • 3.7v 500mAh Lithium Ion Polymer Battery
      • Flight Computer: ATSAMD21G18 ARM Cortex M0 processor
      • 915 MHz radio
      • Power and safety switches
      • Igniter cables
      • 9V battery
    • Developed in C++

      The integrated Launch Station


Section 2: Flight Software Architecture

Section 2.1: FAURO's FSW Architecture OVerview

While those FAURO-specific conventions are more aesthetic in nature, external standards are also in effect to make the code more reliable and fault tolerant. In 2009, NASA's Jet Propulsion Laboratory published the JPL Institutional Coding Standard for the C Programming Language. As this standard aligns nicely with the objectives for this project, it was consulted extensively to improve FAURO's FSW.

Section 2.2: Board Support Packages, Device Drivers, and Libraries

In order for everything to work properly, the following board support packages and libraries must be installed:

Section 3: Testing

While extensive unit testing and Hardware in the loop testing is not yet implemented, basic examples of this functionality exist for the FswManager component. The build files can be generated with the command fprime-util generate --ut, compiled with the command fprime-util build --ut, and run with the command fprime-util check.

Section 4: The Ground Segment

The Ground Segment comprises the Base Station, Launch Station, and Ground System.

Section 4.1: Embedded Base Station and Launch Station Code

Code for the Base Station can be found in the top level project directory. It is designed to be lightweight and simple since the task it performs is simple. The Base Station:

  • receives any data transmitted on the radio for relay back to the host computer so it can be displayed with the Ground System
  • sends FSW commands from the operator to AURO

Code for the Launch Station can is not yet implemented for FAURO. In AURO, its purpose was also simple so the code will be lightweight. The launch station:

  • listens on the radio link for one of the few FSW commands from the Base Station that requires it to act
  • takes the commanded action (namely energize a non-latching relay to complete the launch circuit and ignite the rocket motor)
  • report with LAUNCH level EVRs the launch station's actions

For both the Base Station and Launch Station, transmission on the radio link is only allowed if AURO cedes transmission rights by initiating a Groundspeak session. FAURO does this by transmitting a special packet to indicate some other system may transmit for a short time. The Ground System implements logic that deconflicts usage of the Groundspeak session between the Base Station and Launch Station by disabling user transmission of FSW commands for a short time.

Section 4.2: Use of the F' GDS

While the aURO project had a custom-made GDS, building that was mostly done out of necessity. Since the main purpose of this series of projects is to develop FSW expertise, the fact that F' ships with a a basic ground system was helpful and allowed greater focus on the FSW. FAURO works nicely with the F' GDS out of the box, but one small modification was made to display the unix epoch offset in seconds in the terminal each time FAURO reset. This allows the operator to use the TIME_FROM_EPOCH_SETcommand so the GDS-reported time for telemetry matches the actual time.

Section 5: Hardware Integration

Section 5.1: Purchased Parts List

Section 5.2: 3D Printed Parts and Assembly Hardware

Section 5.3: FAURO Integration

  1. Melt embedment nuts into 6 holes on the Fixed Avionics Bay using soldering iron
  2. Melt embedment nuts into 2 holes on the side of the Removable Avionics Bay where the Battery Enclosure screws enter
  3. Melt embedment nuts into 4 holes on the side of the Removable Avionics Bay where the board mounts
  4. Add screw standoffs to the 4 holes where the board mounts
  5. Solder a jumper from pin 12 to the reset pin on Adafruit Feather M0 Adalogger
  6. Solder jumper from pin 11/A to pin RST on Adafruit Radio FeatherWing
  7. Solder jumper from pin 6/D to pin CS on Adafruit Radio FeatherWing
  8. Solder jumper from pin 5/E to pin IRQ on Adafruit Radio FeatherWing
  9. Solder the spring antenna into the antenna hole on the Adafruit Feather M0 Adalogger
  10. Solder Female Header Set to Adafruit Feather M0 Adalogger with black connector on the top side of the board
  11. Solder Stacking Header to Adafruit Radio FeatherWing with black connector on the top side of the board
  12. Solder Male Header Set to Adafruit LSM6DSOX + LIS3MDL FeatherWing - Precision 9-DoF IMU with the longer portion of the pins on the bottom side of the board
  13. Screw the Adafruit Feather M0 Adalogger into the Removable Avionics Bay
  14. Insert the stacking header male pin into the Adafruit Feather M0 Adalogger female pins
  15. Insert the IMU male pins into the stacking header female pins
  16. Add a standoff to two holes that share a long side of the IMU using a nut from the screw kit
  17. Screw the GPS antenna into one of the two standoffs on the IMU
  18. Screw the BMP sensor into the other standoff on the IMU
  19. Use the two STEMMA QT cables to connect the IMU and GPS and the GPS and BMP
  20. Thread the battery cable through the opening, place the battery in the appropriate position, and attach the battery enclosure with screws
  21. As desired, finish assembly by plugging in the battery, adding the SD card, and connecting the Removable and Fixed Avionics Bays

    The integrated FAURO system
      

Section 5.4: Base Station Integration

  1. Melt embedment nuts into the 8 2.5mm holes on the Base Station base using soldering iron
  2. Insert four standoff screws on the bottom surface of the inside of the Base Station base
  3. Solder uFL SMT connector to appropriate pad on the Adafruit Feather M0 RFM69HCW
  4. Mount the Adafruit Feather M0 RFM69HCW board inside the Base Station using the standoffs and M2.5 screws
  5. Mount the LoRa Antenna to the hole in the Base Station top
  6. Connect the Lora Antenna cable to the uFL connector that was previously soldered
  7. Mount the top of the Base Station to the base using M2.5 screws

    The integrated Base Station
      

Section 5.5: Launch Station Integration

  1. Melt embedment nuts into the 9 2.5mm holes on the Launch Station base using soldering iron
  2. Insert four standoff screws on the bottom surface of the inside of the Launch Station base
  3. Mount the illuminated toggle switches in the two appropriate holes (the larger two) on the Antenna Top
  4. Mount the LoRa Antenna to the remaining hole in the antenna top
  5. Solder uFL SMT connector to appropriate pad on the Adafruit Feather 32u4 RFM69HCW
  6. Solder the Female Header Set to the Adafruit Feather 32u4 RFM69HCW with the black connector portion facing the top of the board
  7. Solder the Male Header Set to the Adafruit Non-Latching Mini Relay FeatherWing so that the longer portion of the pin faces the bottom of the board
  8. Connect the Adafruit Feather 32u4 RFM69HCW and Adafruit Non-Latching Mini Relay FeatherWing using the pins soldered
  9. Cut and splice the JST-PH Battery Extension Cable - 500mm and the Lithium Ion Polymer Battery so that red wire can be run through the green toggle switch
  10. Attach the wiring, battery, green switch, and Adafruit Feather 32u4 RFM69HCW such that the board is only powered when the green toggle is flipped up and lighted
  11. Wire the 9V battery, red switch, relay, and launch wiring so that the circuit can only completed if the red toggle is flipped up and lighted
  12. Solder the jumper wire from pin 12 to the relay set pin
  13. Connect launch circuit leads to the appropriate relay outputs
  14. Mount the boards to the Launch Station using the standoffs and M2.5 screws
  15. Place the Lithium Ion Polymer Battery and 9V battery in the appropriate compartments
  16. Mount the top of the Launch Station to the base using M2.5 screws

    The integrated Launch Station
      

Section 6: To Clone, Compile, and Run This Project

TO BE COMPLETED - procedure for cloning the project properly

Section 7: To Setup Similar Environment and Project From Scratch

TO BE COMPLETED - procedure for how this project was setup from scratch

Section 8: Operations

  1. Force the Feather M0 to enter programming mode by doing EITHER:
    • Double tap the physical reset button on the microcontroller
    • Using vscode serial monitor, open a connection to the board with a 1200 baud rate then immediately close it. Once programming mode is entered, it is recommended to switch the baud to 115200 immediately to prevent an inadvertent entry into programming mode.
  2. Using the windows explorer GUI, copy the fauro_deployment.bin binary from the WSL filesystem into one directly accessible by Windows. The “Documents” folder will be used here and referenced later on during the command to flash the image.
  3. Confirm the adafruit libraries required for the FeatherM0 are installed in Windows using the Arduino IDE (adafruit and arduino M0/SAMD packages)
  4. Note the complete file path of the Windows copy of the binary and the COM port for use in the command below. The following powershell command may be used to ascertain the correct COM port:
    • usbipd list
  5. Flash the image using the following Powershell command:
    • C:\Users\snowicane\AppData\Local\Arduino15\packages\adafruit\tools\bossac\1.8.0-48-gb176eee/bossac.exe -i -d --port=COM22 -U -i --offset=0x2000 -w -v C:\Users\snowicane\Documents\Fauro.bin -R
  6. Once flashing completes, the serial monitor of vscode can be used to confirm the target is active and printint things over the serial connection
  7. Bind and attach the base station or target device to WSL so the serial data can be fed to the GDS. Note, if you wish to bind to the target device directly the serial connection opened in step 6 must first be closed. The following powershell command can be used with the appropriate busid from the usbipd command above:
    • usbipd bind --busid 1-10
    • usbipd attach --wsl --busid 1-10
    • Note that usually the bind command is only required once even if the board is disconnected and reconnected
    • Note that the command to detach a port is:
      • usbipd detach --busid 1-10
  8. On the linux side, the following two commands can be used to see the attached COM port was successful:
    • lsusb
    • ls /dev/tty* (will usually be attached as ttyACM0)
  9. Run the GDS with the following linux command:
    • `fprime-gds -n --dictionary ./build-artifacts/featherM0/Fauro/dict/FauroTopologyAppDictionary.xml --comm-adapter uart --uart-device /dev/ttyACM0 --uart-baud 115200



FAURO demo video
https://youtu.be/RNxwbEgiWnk

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