/******************************************************
* Josh Schoolcraft <joshua.schoolcraft@jpl.nasa.gov>
* Thomas A Werne <thomas.a.werne@jpl.nasa.gov>
******************************************************/
~
"authors.h" 4L, 215C
4,2
All
Copyright 2014 California Institute of Technology. Government sponsorship acknowledged.
“If you want to make an apple pie
from scratch, you must first create the
universe.”
2
\mainpage
• Intro
• INSPIRE
• Architectures
• Development
• The Code
• Reflections
3
\people
• Communications Networks
• Instrument Flight Software
and Ground Support
• Instrument Flight Software
and Ground Support
4
Interplanetary NanoSpacecraft Pathfinder In a Relevant Environment
Low-cost mission leadership with the world’s first CubeSat beyond Earth-orbit
PI: Dr. Andrew Klesh, Jet Propulsion Laboratory, California Institute of Technology
PM: Ms. Lauren Halatek, Jet Propulsion Laboratory, California Institute of Technology
University Partners:
• Cal Poly - San Luis Obispo
• U. California – Los Angeles
• U. Michigan – Ann Arbor
• U. Texas – Austin
Collaborator:
• Goldstone-Apple Valley Radio Telescope (GAVRT)
Copyright 2014 California Institute of Technology. Government sponsorship acknowledged.
5
\INSPIRE
Overview:
X-Band Patch Antennas (JPL)
[two sets]
ISIS UHF Antenna
Volume: 3U
(10x10x30cm)
Data Rate: 62-256000
bps
Magnetometer (JPL)
Communications:
Primary: X-band via DSN
Secondary (Receive only):
DSS-28 (GAVRT), &
Secondary Stations
Relay: UHF
Cold-Gas ACS (U. Texas)
Star Tracker
(Blue Canyon)
Science:
Magnetometer
Camera + Processing
Board
C&DH Board +
Lithium UHF (AstroDev)
Processing Board
(Tyvak)
Guidance and Control:
Star Tracker
Gyroscope
Sun Sensors / Solar Cells
Cold-Gas Thrusters
Deployable Solar Panels (Pumpkin)
Structure (JPL)
Iris X-Band Radio (JPL)
6
\INSPIRE
• Small project (<$5.5M) with small focused team (core of 9
people) for short mission duration (<90 days) in deep space
with redundant spacecraft.
• Development: 18 months from start to finish
• Delivered on time and under budget
• Built on extensive CubeSat experience in low-Earth orbit
(personnel, practices, and hardware heritage)
• Small, skilled, multidisciplinary team
• Use existing standards (CubeSat Specification, CCSDS, etc.) to
reduce design complexity
• Large margin for mission success based on demonstrated
capabilities
7
\requirements
• Survive
• Navigate
• Communicate
…Everything else is extra credit…
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\constraints
• Time
• People
• Hardware
…Everything else is secondary…
9
\hardware architecture
• Texas Instruments MSP430 family
• Extremely low power (idle current <1µA)
• Von-Neumann architecture
• JTAG debug (single-step instructions with
full hardware state visibility)
• Not radiation-hardened (yet)
10
\hardware architecture
• Initial design: MSP430F1611
• Flight Heritage
• 8MHz, 10KB SRAM, 64KB program storage
• Final design: MSP430F2618
• 16MHz 8KB SRAM, 116KB Program storage
• 16-bit architecture with 20-bit addressing
• Bus Interfaces: I2C, SPI, UART
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\software architecture
• Organic approach
• Start with a minimal, rock-solid “universe”
• Core real-time operating system “protos”
•
•
•
•
Time
Threads
Memory protection
Cascaded deadline enforcement
• Establish bus communication
• Read and track hardware state
12
\software architecture
• Integrate off-the-shelf ground software
• AMMOS Mission Data Processing and Control System
(AMPCS)
• Establish mission-specific framework
• Support tests with increasing complexity
• Start with peripherals on/off (blinkenlights)
• End with Operational Readiness Tests (and the mission)
13
\development
• Pair coding (“rolling peer reviews”)
• Start from bare metal, add functionality only as needed
• Expect to write subsystems three times:
1.
2.
3.
Prototype
First cut
Final cut
• Work with real hardware
• Write and test in a tight loop
•
•
End-to-end as much as possible with ground software in the loop
Use bug reporting for problems that require discussion and planning
• Spend time to save time
•
•
•
Instrument everything (“Breadcrumbs”), trust nothing
Maintain some modularity
Automate repetitive tasks
• Leverage autocoding
•
Build from tables as much as possible
•
Python + YAML (not XML)
• Simplifiy hardware checkouts
• Interactive RUSH: Really Useful SHell
Merge the CubeSat software development model (amateur code, fast and loose) with
guidance from the agile software development, and a helping of skepticism.
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\nutshell
• Coded ~99% from scratch
• Fault Protection engine
• Multi-threaded RTOS (“protos”)
• Attitude control
• Drivers for 14 hardware devices
• DSN-conformant telecom library
• Protocols: AOS, TC, Space Packet,
CFDP-1, AX.25
• Uplink, downlink, relay
• FAT32 filesystem
• Command sequence engine
• Simultaneous execution
• Mission modes
• Science Campaigns
• Hotfix patching
• Ground support tools
• Umbilical interface
• Autocoded command and telemetry
stubs
• Patch generator
• Sequence generator
• CFDP Depacketizer
15
\codebase
• C (with C99 initializers): 15,000 lines (cloc)
• Libraries - Drivers, Filesystem, Telecom: 50%
• Mission-specific software: 35%
• Core protos OS: 15%
• Assembly: 50 lines
• Stack - register manipulation
• 20-bit address manipulations
• Texas Instruments cl430 compiler
• O2, small_enum, LARGE_CODE_MODEL
• 100KB binary, including reserved spaces
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\runtime
• Stack: 2KB
• 80% utilization at deepest call depth
• Four threads, “executive” round-robin scheduler
• Telecom buffers: 4KB
• Three multi-protocol I/O interfaces: Two radios + ground
umbilical
• Spacecraft state: 1KB
• SD card driver: 512B
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\critical points
•
•
•
•
Stable core
Breadcrumbs
Automation
Hardware in the loop
• Tight write-test-modify loop
18
\parallels
“The original software development for the data computer has essentially
been a two-man show since 1975, beginning when Edgar M. Blizzard joined
Richard Rice to develop the flight version of the code. […]
From start to validation to release, their tools were within sight, and certainly
hearing […].
Rice characterized the unique nature of the computer data software this way:
‘We didn’t worry about top-down or structured; we just defined functions.’”
-Encyclopedia of Computer Science and Technology Vol. 18
“Computers In Spaceflight: The NASA Experience”
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^[:q!