Embedded Systems Development Selecting a language for a

Embedded Systems Development Selecting a language for a real-time embedded system

Embedded Systems • In order to select a language for real-time embedded system we need to ask two questions – What languages are available? – What do we want from these languages?

Embedded Systems • There are four criteria that we can adopt for language selection – Essential features – Primary features – Secondary features – Perfomance

Embedded Systems • Essential features – Assembley language MC interface – Absolute addressing – Access/control of H/W – Bit manipulation – Interrupt handling – Pointers – Specification for time delays – Processor extensions

Embedded Systems • The primary features are: – Well defined language standard – Well defined behaviour – Strong data typing/ Rigorous control structures – Modular structure - seperate compilation – Exception handling – Tasking facilities – RTOS/RTEX interfaces – Maths library well defined

Embedded Systems • The secondary features are: – Good syntax and layout – Multitasking - language and rt support – Interfaces to other HLLs – Safety critical subset/features – Comprehensive libraries – Object Orientated programming constructs

Embedded Systems • The performance features are: – Setting task deadlines – Evaluation of code execution times – Deterministic code – Selection of scheduling strategies – Timing analysis mechanism

Embedded Systems Ada • • Modularity separate compilation tasking exception handling reliable readable portable • • • large language complex weak tasking model no safety critical no OOP (Ada 95)

Embedded Systems C • • • highly efficient easy to learn powerful widely available lots of tools/GUIs • • • difficult to read portability problems no OOP interface undefined behaviour weak type checking

Embedded Systems C++ • • • builds on C Object orientated good type checking portable HLL interfaces • difficult to read • memory leakage • library incompatibility

Embedded Systems Modula 2 • • • Modular construction Systems programming Concurrency interrupt handling portable • not widely used • few compilers • no OOP

Embedded Systems Oberon/Oberon 2 • • • Modular Concurrency interrupt handling Systems programming OOP Support • not widely used • no standard • limited OOP model

Embedded Systems • Assembly language and MC interface – Ada - standard library package or pragma – C - embedded with asm or function call – C++ - similar to C – Modula 2 - no defined standard facilties – Oberon-2 - highly systems dependant

Embedded Systems • Absolute addressing – Ada - type ADDRESS in SYSTEM package – C - uses pointers – C++ - as with C or library interfaces – Modula 2 - SYSTEM library – Oberon-2 - as with Modula 2

Embedded Systems • Well defined language standard? – Ada - Yes – C - Yes but compiler differences exist – C++ - still evolving – Modula 2 - Yes but few around – Oberon-2 - informal standard

Embedded Systems • Well defined behaviour? – Ada - yes few differences – C - No large discrepancies – C++ - No better than C – Modula 2 - yes rigorous – Oberon-2 - evolving but strict

Embedded Systems • Strong type checking? – Ada - yes very strong – C - very weak use of pointers – C++ - better than C but pointer problems – Modula 2 - strongly typed – Oberon-2 - strongly type OOP features?

Embedded Systems • Rigorous control structures? – Ada - yes but has goto – C - care needed with switch, for and jumps – C++ - similar to C – Modula 2 - yes but has EXIT/RETURN – Oberon-2 similar to Modula 2

Embedded Systems • Modular structure/ seperate compilation? – Ada - Yes built into language – C - Yes, pointer problems – C++ - no explicitly modular - can have class – Modula 2 - Yes, implemantation & definition – Oberon-2 - similar to Modula 2, implementation

Embedded Systems • Exception handling – Ada - standard for language & user defined – C - no standard use jumps – C++ - version 3. 0 support it – Modula 2 - no standard - some support – Oberon-2 - no standard

Embedded Systems • Tasking? – Ada - yes built in – C - no can be implemented with pointers – C++ no can be implemented – Modula 2 - yes using PROC – Oberon-2 - can be implemented

Embedded Systems • Syntax and layout – Ada - Good highly readable – C - well specificed syntax but bad overall – C++ - even worse than C – Modula 2 - highly readable EBNF/VDM – Oberon-2 - very readable EBNF

Embedded Systems • Multitasking rt support – Ada - integral part of language – C - not supported – C++ - not supported libraries? – Modula 2 - implemented using coroutines – Oberon-2 - optional library feature