1. cFE FSW at APL & FSW Reusability
C. Monaco

2. Spark discussion in the community regarding best practices for
Overview
APL use of cFE
Application Template
Libraries
Spark discussion in the community regarding best practices for
Abstracting HW & Platform
Increasing the reusability of FSW
Use of drivers

3. + cFE at APL cFE & OSAL Van Allen Probes
First use of cFE (cFE & OSAL 2.11)
RAD750, VxWorks 6.4
Two spacecraft
Earth orbiters
Launched 8/30/2012
Predecessor APL missions STEREO and MESSENGER did not use cFE & OSAL middleware
Much of the APL FSW infrastructure was able to be adapted into the cFE environment
cFE & OSAL +

4. cFE at APL 2011 – 2012 - JHU APL / GSFC IRAD efforts Solar Probe Plus
Memory Protection IRAD
cFE running in user-mode on an embedded system running VxWorks 6.7
Multi-Core IRAD
cFE systems running in Asymmetric Multiprocessing (AMP) & Symmetric Multiprocessing (SMP)
Solar Probe Plus
One spacecraft (SC) with 3 Single Board Computers (SBCs)
2018 Launch
Flight Software
RTEMS 4.10
APL developed SBC with UT699E
cFE 6.4.0, OSAL 4.1
Testbed
RedHawk Linux – with real-time kernel patch
Hosts emulations of SC components that are unavailable on a particular testbed

5. Application Commonality
During the development of Van Allen Probes FSW it was recognized that applications that use cFE have a lot in common
Initialization with cFE
Initialization with scheduler (SCH) application
Housekeeping telemetry generation
Initialization of parameter management
Some common commands
Common features
Counters
Telltales
Message processing (message & response handler infrastructure)
Command processing (command & response handler infrastructure)
All applications need to be maintained

6. Application Template
A Common Application Template was developed under Van Allen Probes
Van Allen Probes: Each APL-Developed FSW application will be built upon a Common Application Template
Isolate infrastructure from application-specific functionality
Jump-start software development for new applications
Allow developers to focus on the personality of each application rather than the basic application infrastructure
Provides application uniformity & simplification of software maintenance
The Common Application Template is cloned to create new applications
Reduces code review materials
Reduces unit test effort
References to TMP within the template source are automatically converted to the mnemonic for the application
TMP_AppWakeup()  becomes AUT_AppWakeup()

7. Application Template – reusability and maintainability
The Application Template exists in separate source files from the application-specific code
Maintaining the Application Template is similar to maintaining a middleware
The APIs have an incentive to remain the same
The implementation may be changed
The updated template can be deployed to existing applications and new applications alike
With zero or minimal disruption to existing applications

8. APL cFE Applications
OSAL allows the software applications to be abstracted from the OS
cFE helps abstract one application from another
Rather than making direct function calls (whose APIs could change) from one application to another, messages are sent on the software bus
Applications
Some C&DH applications are highly re-usable – have no SC / platform dependencies
Some FSW applications have some SC / platform dependencies but are otherwise largely independent of the SC / Platform
Other applications are very dependent upon the SC / Platform

9. APL cFE Applications
A goal was to maximize the potential for reuse of FSW applications from mission to mission
A goal was to facilitate FSW development on the ubiquitous linux platform
Free up valuable test-bed time
Therefore, a design objective of the APL Flight Software Application was to (within reason) abstract the hardware from the applications

10. APL Libraries for cFE Systems
Some FSW libraries exist to provide common functionality to multiple applications
Table management
Utility functions, etc.
Some FSW libraries exist to provide an abstraction to SC or HW
Enable development on pc-linux platform
Enhances reuse for subsequent missions.

11. APL Libraries for cFE Systems
Memory Object Handler
An example of a SC / platform independent library
Rather than using the cFE Table Services, much of the APL legacy flight software used “Memory Objects”
Custom parameter management system was subsequently ported to the cFE environment as MOH_lib
Applications “Register” with the Memory Object Handler Library:
Register “memory object type” with the library
Register “memory object IDs”
Individual memory objects or a group if the same kind of memory object
Register call-back functions to allow access, manipulation and verification of the registered objects
Provides mechanism for modifying, uplinking, downlinking the contents of selected tables or internal data structures

12. APL Libraries for cFE Systems
EEPROM Library
Van Allen Probes had EEPROM non-volatile memory
This library abstracted the details of EEPROM from the applications that required access: EE_Read(), EE_Write(), EE_WriteEnableDisable(), etc.
A simple port of this library was created to emulate EEPROM using a file for pc-linux
This allowed development on Van Allen Probes to proceed in the pc-linux environment
The existence of this library allowed the software that used it to be portable to other NVM technologies through a different port of the library
APL BSP Library
Interface to timers for scheduler (SCH) application interrupt and synchronization
Which NVM image was booted and is running
Collect CPU utilization metrics
Check validity of RAM addresses
A port exists for Van Allen Probes, PC Linux, and SPP

13. APL Libraries for cFE Systems
SSR Library
Access to SSR registers
SSR DMA
Provide housekeeping specific to the SSR hardware
Provide consistent access to SSR by FSW applications
Mutual exclusion, maintenance of applicable state information
SCIF Library
Most spacecraft specific
Opportunity for reuse across missions is minimal
Enables FSW to run on pc-linux for the particular mission
Abstraction of uplink/downlink hardware
Abstraction of Spacecraft Interface (SCIF) HW
Abstraction of the SpaceWire Router
Abstraction of other mission unique hardware

14. APL Libraries for cFE Systems
Source code for the libraries is either
Flat: for libraries that exist to provide common functionality across multiple applications
MOH_lib/<source>.c
Parallel: for libraries that exist to abstract SC or platform
SCIF_lib/shared/<source>.c
SCIF_lib/spp-sbc/<source>.c
SCIF_lib/pc-linux/<source>.c
Environment variables in the build (similar to those that help locate the PSP port) are used to select the library port.

15. Follow Up The community could benefit from more discussion on
Best practices of use of Drivers & Libraries