Cubesat Space Protocol

Last updated
Cubesat Space Protocol
Communication protocol
AbbreviationCSP
Purpose CubeSat
Developer(s)Johan de Claville Christiansen
IntroductionApril 26, 2010;15 years ago (2010-04-26)
OSI layer 1, 2, 3, 4
CubeSat Space Protocol
Original author(s) Johan de Claville Christiansen
Developer(s) SpaceInventor, GomSpace, Space Cubics
Initial releaseApril 26, 2010;15 years ago (2010-04-26)
Stable release
2.0 / April 19, 2024;13 months ago (2024-04-19)
Repository github.com/libcsp/libcsp
Written in C, Python
Operating system FreeRTOS, Linux, Zephyr, Mac OS X, Windows
Type Protocol
License MIT License
Website www.libcsp.org

CubeSat Space Protocol (CSP) is a small network-layer delivery protocol designed for CubeSats.[ citation needed ] The idea was developed by a group of students from Aalborg University in 2008, and further developed for the AAUSAT3 CubeSat mission that was launched in 2013. The protocol is based on a 32-bit header containing both network and transport layer information. Its implementation is designed for embedded systems such as the 8-bit AVR microprocessor and the 32-bit ARM and AVR from Atmel. The implementation is written in C and is ported to run on FreeRTOS, Zephyr and POSIX and pthreads-based operating systems such as Linux. The three-letter acronym CSP was adopted as an abbreviation for CAN Space Protocol because the first MAC-layer driver was written for CAN-bus. The physical layer has since been extended to include several other technologies, and the name was therefore extended to the more general CubeSat Space Protocol without changing the abbreviation.

Contents

The protocol and the implementation is still actively maintained by Johan de Claville Christiansen, Space Inventor, GomSpace, and Space Cubics. [1] The source code is available under an MIT License and hosted on GitHub.

Description

The CubeSat Space Protocol enables distributed embedded systems to deploy a service-oriented network topology.[ citation needed ] The layering of CSP corresponds to the same layers as the TCP/IP model. The implementation supports a connection-oriented transport protocol (Layer 4), a router-core (Layer 3), and several network-interfaces (Layer 1–2). A service-oriented topology eases the design of satellite subsystems, since the communication bus itself is the interface to other subsystems. This means that each subsystem developer only needs to define a service-contract, and a set of port-numbers their system will be responding on. Furthermore, subsystem inter-dependencies are reduced, and redundancy is easily added by adding multiple similar nodes to the communication bus.

Key features include: [ citation needed ]

Operating systems supported

CSP should compile on all platforms that have a recent version of the gcc compiler. CSP requires support for C99 features such as inline functions and designated initializers.

Physical layer drivers

CSP supports several physical layer technologies. The source code contains an implementation of a fragmenting CAN interface and drivers for SocketCAN and the Atmel AT90CAN128, AT91SAM7A1 and AT91SAM7A3 processors. From version 1.1 onwards, CSP also includes interfaces for I2C and RS-232. Interfaces need only to implement a function to transmit a packet, and insert received packets into the protocol stack with the csp_new_packet function. CSP has been successfully tested on top of the following layers:

Protocol header

Version 1

The port range is divided into three adjustable segments. Ports 0 to 7 are used for general services such as ping and buffer status, and are implemented by the CSP service handler. The ports from 8 to 47 are used for subsystem specific services. All remaining ports, from 48 to 63, are ephemeral ports used for outgoing connections. The bits from 28 to 31 are used for marking packets with HMAC, XTEA encryption, RDP header and CRC-32 checksum.

CSP Header 1.x
Bit offset31302928272625242322212019181716151413121110 9 8 7 6 5 4 3 2 1 0
0PrioritySourceDestinationDestination
Port		Source
Port		ReservedH
M
A
C		X
T
E
A		R
D
P		C
R
C
32Data (0 – 65,535 bytes)

Version 2

CSP Header 2.x
Bit offset4746454443424140393837363534333231302928272625242322212019181716151413121110 9 8 7 6 5 4 3 2 1 0
0PriorityDestinationSourceDestination
Port		Source
Port		ReservedH
M
A
C		X
T
E
A		R
D
P		C
R
C
48Data (0 – 65,535 bytes)

References

  1. ↑ https://github.com/libcsp/libcsp/blob/develop/AUTHORS
  2. ↑ "The Protocol Stack". The Cubesat Space Protocol. Retrieved 2025-06-04.
  3. ↑ "TM Synchronization and Channel Coding CCSDS 131.0-B-1 Blue Book" (PDF). September 2003. Retrieved December 9, 2022.
  4. ↑ "TM Synchronization and Channel Coding Recommended Standard CCSDS 131.0-B-2" (PDF). August 2011. Retrieved December 9, 2022.
  5. ↑ "Information Processing and Digital Communications in a Modular Satellite".
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