Control & Data Handling,Control & Data Handling,Operator Control, Operator Control,

Aircraft Interface to C&DHAircraft Interface to C&DH

Steve Musko

Space Physics Research Laboratory

University of Michigan

Ann Arbor, MI USA

College of EngineeringSpace Physics Research Laboratory

Department of Atmospheric, Oceanic & Space Sciences

LRR-X Internal Concept ReviewNASA Goddard Space Flight Center

23 April 2002

Musko, 23 Apr 02 C&DH, LRR-X Concept Review 2 of 17

OutlineOutline

• C&DH Block Diagram & Aircraft Interface• Requirements• Operating System• Flight Software Architecture• Telemetry• Commands• Operator Laptop Software

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C&DH Block Diagram &C&DH Block Diagram &Aircraft InterfaceAircraft Interface

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PC-104 Stack (front)PC-104 Stack (front)

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PC-104 Stack (back)PC-104 Stack (back)

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Flight SoftwareFlight SoftwareRequirementsRequirements

• Collect– Science data from the correlator board– Analog housekeeping values from the analog I/O board– Time and position from the GPS receiver– Aircraft status from RS-232 port

• Combine science data, analog housekeeping, GPS time and position and aircraft status into real-time telemetry (TM) packets and one-minute TM files

• Store TM files in flash memory• Communicate with operator laptops via Ethernet

– Receive and execute commands – Transmit real-time TM packets to laptops– Support bulk FTP data uploads from flash memory

• Control temps using PID algorithm

Musko, 23 Apr 02 C&DH, LRR-X Concept Review 7 of 17

Flight SoftwareFlight SoftwareOperating SystemOperating System

• QNX operating system– Real time, preemptive, multiprocess, multithread,

multiprocessor

– PC compatible (and other processors)

– Complete set of utilities (FTP, Telnet, drivers etc.)

– 20 year company track record

– Scalable: OS features can be added as needed

– Reliable:• Microkernel architecture

• Processes execute in separate memory spaces

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Flight SoftwareFlight SoftwareQNX ArchitectureQNX Architecture

DeviceDriver

Application

- QNX provides complete memory protection

- Applications, drivers and OS components arearchitecturally equivalent- All processes run in separate memory spaces- Processes are much less likely to crash each other- OS features and drivers can be added dynamically- All interprocess communication is accomplishedusing microkernel message passing

Microkernel

TCP/IPStack

FileSystem

Application

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Flight Software ArchitectureFlight Software Architecture

LRR-XApplication

Microkernel

TCP/IPStack

DOSFile

System

TelnetServer

FTPServer

NetworkI/F

Driver

SerialPort

Driver

PseudoTerminal

Driver

ConsoleDriver

Flash DiskDriver

Korn ShellMisc. Shell

Utilities

Musko, 23 Apr 02 C&DH, LRR-X Concept Review 10 of 17

Flight SoftwareFlight SoftwareLRR-X App ArchitectureLRR-X App Architecture

• The LRR-X application is a collection of threads that communicate with each other via QNX message passing– Read_Hskp_Thread

– Read_Sci_Data_Thread

– Form_TM_Pkts_Thread

– Store_TM_Files_Thread

– Send_Real_Time_TM_Thread

– Process_GSE_Cmds_Thread

– Read_GPS_Data_Thread

– Sync_With_GPS_Time_Thread

– Cntl_Temps_Thread

– Check_Limits_Thread

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Flight SoftwareFlight SoftwareTelemetryTelemetry

• TM packets are combined into one minute TM files and stored on flash disk. Filenames are derived from TM packet time tags.

• All TM packets are transmitted in real time to the operator laptop computers

• TM files on flash disk can be uploaded to the the operator laptop computers using FTP any time the instrument is powered up (even while the LRR-X application is running).

• There is a single TM packet type that contains science data, housekeeping, GPS time and position and aircraft status

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TM Packet ContentsTM Packet Contents

TM Packet Field Size (Bytes)

Packet Type Identifier & Length 4

Packet Serial Number (from correlator board) 4

GPS Time Tag 8

GPS Position (lat, long, altitude) 30

Aircraft Attitude (roll, pitch) 20

Analog Housekeeping Group Number (0..7) 1

Subcommutated Analog Hskp Group Values (12 values x 2 bytes) 24

Temp PID Loop Group Number (0..7) 1Subcommutated Temp PID Coefficients, Setpoints & Duty Cycles(4 PID loops x 5 values x 4 bytes) 80

ADC Lookup Table Values 14

Correlator Values (378 channels x 4 samples x 2 bytes) 3024

Totalizer Values (1008 totalizers x 2 bytes) 2016

Total TM Packet Size à 5226

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Flight SoftwareFlight SoftwareTM Rate & Storage CapacityTM Rate & Storage Capacity

• Total TM packet size is 5226 bytes• TM production rate is 3.03 Hz x 5226 bytes =

15,835 bytes/sec (54.4 Mbytes/hour)• 940 Mbytes of Flash memory provides 17.3 hours

of TM file storage

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Instrument CommandingInstrument Commanding

• The instrument executes command scripts• Command scripts are:

– Text files that are edited on the operator laptop

– Downloaded to flight computer flash memory

• At initialization, the flight software loads and runs a default command script if it exists on flash disk

• All commands can be sent individually directly from the operator laptop

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Sample Command ScriptSample Command Script

PID_1_Pro_Coeff = 1.98PID_1_Int_Coeff = 0.0228PID_1_Drv_Coeff = 0.276PID_1_Setpoint = 24.0

PID_2_Pro_Coeff = 2.33PID_2_Int_Coeff = 0.0166PID_2_Drv_Coeff = 0.158PID_2_Setpoint = 24.0

Trunc_Map_E1 = 3367HTrunc_Map_O1 = 3367HTrunc_Map_E2 = 3509HTrunc_Map_O2 = 3509H

execute Calibration_Setup.cmdstart_data_collection

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Instrument CommandsInstrument Commands

• Set PID temp loop control values• Set truncation map values• Set Test Control Register value• Execute command script (for nested scripts)• Start data collection• Stop data collection

Musko, 23 Apr 02 C&DH, LRR-X Concept Review 17 of 17

Operator LaptopOperator LaptopSoftware RequirementsSoftware Requirements

• Store real time TM packets on laptop hard disk• Display real time or stored science TM in several forms

– Polar Visibility Plot– Raw correlator and totalizer values– Brightness Temperature Image

• Display real time or stored housekeeping TM in tabular and strip chart form

• Alert the operator if any critical housekeeping limit is exceeded

• Support command script editing and execution• Support individual command execution• Support FTP file transfer with the instrument flash disks

and the aircraft FTP file server