9/25/2002 Interface from Command & Data Handling (C&DH) to Control System

9/25/2002 C&DH System Architecture One Ada package is used to integrate the application Contains procedures to perform the following: –Initialization –Rate processing (one task per rate) 80 Hz 10 Hz 5 Hz 1 Hz 0.1 Hz –Inter-task I/O

9/25/2002 Ada Restrictions System Architect has provided restrictions on use of Ada constructs –No “delay” statements Wants a single, periodic, interrupt –All dynamic memory allocations (“new”) must be performed in initialization code Worry about memory fragmentation Worry about memory leaks –Use up to optimization level 2 (“-O2” compilation flag) Worry about code generator at level 3 –Use dynamic elaboration checking (-gnatE compilation flag) Needed for DMS Requires use of pragma Elaborate or Elaborate_all to avoid Program_Error exception

9/25/2002 Package Application_Interface with Cyclic_Index_Types; package Application_Interface is procedure Initializations; procedure Eighty_Hz_Processing; procedure Eighty_Hz_Io; Ten_Hz_Offset : Cyclic_Index_Types.Offset_Type; procedure Ten_Hz_Processing; procedure Ten_Hz_Io; Five_Hz_Offset : Cyclic_Index_Types.Offset_Type; procedure Five_Hz_Processing; procedure Five_Hz_Io; One_Hz_Offset : Cyclic_Index_Types.Offset_Type; procedure One_Hz_Processing; procedure One_Hz_Io; Tenth_Hz_Offset : Cyclic_Index_Types.Offset_Type; procedure Tenth_Hz_Processing; procedure Tenth_Hz_Io; end Application_Interface;

9/25/2002 GN&C Interface With C&DH Sensor data is configured to simply “arrive” periodically Actuator data is automatically sent periodically Various I/O procedures used to move data

9/25/2002 Good Programming Practice Minimal processing in I/O procedures –They are called within the 80 Hz task –Should simply copy data from local objects to global objects 80 Hz Task 10 Hz Task 80 Hz processing 10 Hz I/O Signal 10 Hz task 10 Hz Task processing

9/25/ Second Frame (Theoretical) 10 Hz 80 Hz 5 Hz 1 Hz 0.1 Hz

9/25/ Second Frame (Real) 10 Hz 80 Hz 5 Hz 1 Hz 0.1 Hz 1 pass 10 passes 80 passes

9/25/2002 I/O Inputs Mode commands Reference frame Attitude command GPS attitude data (initialization only) Star Tracker data Inertial Sensor Assembly (ISA) data Reboost start time Reboost end time Outputs Thruster commands