Programming RTEMS applications with Ada

120 Pages·2013·0.47 MB·English

Programming Real-Time Embedded
systems : Ada 2005 and RTEMS
Frank Singhoff
Office C-202
University of Brest, France
[email protected]
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Summary
1. Introduction and sequential programming.
2. Concurrency features.
3. Real-Time features.
4. Examples of Ada runtimes.
5. Conclusion.
6. References.
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Introduction to Ada (1)
• Why this language for Real-Time embedded systems:
Has concurrency and real-time features: task, interruptions, synchronization, timers,
real-time scheduling features,...
International ISO standard (portability).
Separate compilation (large software).
Provides numerous reliability mechanisms (e.g. strong typing).
Complex language.
• Domains: transportations (train, aircraft, spacecraft) and military devices.
• Examples: Airbus (320, 380), Boeing (777), Fokker, Tupolev, Eurostar, Underground (line
14 of Paris), TGV, Ariane (4 and 5), Satellites (Intersat), spacecraft (Cassini, Huygens, Soho,
Mars Express), military (Tiger, Apache, Patriot) =⇒
http://www.seas.gwu.edu/ mfeldman/ada-project-summary.html.
• Historical matters: Ada 83, Ada 95, Ada 2005, Ada 2012.
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Introduction to Ada (2)
1. What is an Ada program?
2. Types, operators, variables, constants.
3. Flow of control.
4. Inputs/Outputs.
5. Pointers and dynamic allocations.
6. Generic packages.
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What is an Ada program (1)
•
Separate compilation: unit of program = unit of
compilation.
•
Types of program units (GNAT files) :
Main procedures: entry point of a program (.adb file).
Packages: set of declarations (subprograms, types, tasks, ...).
Public part: (package specification, .ads file).
Hidden/private part: (package body, .adb file).
Tasks : specification (.ads file) and body (.adb file).
Generic units: units that are parametrized (packages or
subprograms). Possible parameters: types, constants, subprograms
or packages.
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What is an Ada program (2)
•
Structure of a main procedure:
with package_name1 ; use package_name1 ;
with package_name2 ; use package_name2 ;
procedure main_procedure_name i s
−−
declarations
begin
−−
statements
end main_procedure_name ;
File main_procedure_name.adb
with and use clauses.
⇒
Use is optional (pointed notation otherwise) = do not use them for
reliable software.
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What is an Ada program (3)
•
Example of a main procedure:
w i t h t e x t _ i o ;
use t e x t _ i o ;
procedure H e l l o i s
begin
Put_Line ( " H e l l o world " ) ;
end H e l l o ;
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What is an Ada program (4)
•
Structure of a package specification:
package package_name i s
−−
p u b l i c d e c l a r a t i o n s
p r i v a t e
−−
p r i v a t e d e c l a r a t i o n s
end package_name ;
•
Structure of a package implementation:
package body package_name i s
−− −
sub programs
begin
−−
i n i t i a l i z a t i o n o f the package
end package_name ;
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What is an Ada program (5)
•
Package specification (file mypackage.ads) :
package mypackage i s
procedure sum( a : in in t e g e r ;
b : in in t e g e r ; r e s u l t : out in t e g e r ) ;
f u n ct io n sum( a : in in t e g e r ; b : in in t e g e r )
return in t e g e r ;
p r i v a t e
i n t e r n a l _ v a r i a b l e : in t e g e r ;
end mypackage ;
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What is an Ada program (6)
•
Package implementation (mypackage.adb) :
package body mypackage is
procedure sum(a : in integer ;
b : in integer ; result : out integer ) is
begin
result :=a+b+internal_variable ;
end sum;
function sum(a : in integer ; b : in integer )
return integer is
begin
return a+b+internal_variable ;
end sum;
begin
internal_variable :=100;
end mypackage;
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