DO254 A Beginners View Duncan Brooks

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DO-254 A Beginners ViewDuncan Brooks

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In the beginning ..
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Obvious Questions

• How much will my process have to change?
• How much will this cost?
• Can I convince the HW section to code VHDL to a
  standard?
• How will I obtain independence?
• Is it time to find another job?

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Presentation Overview

• The projects
• The document itself
• Experience of implementing the different stages
• Things I like
• Things I dont like
• Suggestions

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The Projects

• Avionics products
• Software and hardware
• Level B and Level C
• FPGA with VHDL implementation

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The Document - Initial Thoughts

• Read it 3 times understood
• (DO178B not really until read
• the explanation DO248B)
• Its about time -
• Programmable logic has the potential to be much
  more complex than software
• Can I get away with simple hardware?
• 100 testing or not?

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When is Hardware not Hardware?

• When its software! Soft cores?
• What about timing violations?
• What about temperature effects?
• What about COTs programmable hardware? E.g. DSPs
  and microcontrollers.

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How do I get my Process to fit in?

• Can I merge the stages?

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Design
Planning
Requirements Capture
Requirements Capture
Conceptual Design
Design
Detailed Design
Code simulate
Implementation
Hardware Test
Production Transition
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Simulation and Testing

• Where do simulations fit in?
• Verification?
• Need to certify the simulation tool hard
• So why simulate?
• But designers will use it anyway!
• Automated testing is essential for complex logic

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Independence

• Am I going to have to find another engineer?

• Then I discovered Appendix A
• Acceptable means-
• Test cases or procedures developed by the
  designer are reviewed by another individual
• It is not the intent of independence to require
  someone other than the designer to execute the
  tests once they are evaluated or developed with
  independence.
• Major variance from DO178B ? Less rigorous.

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In the end .

• Two certified products, one at level B and one at
  level C
• It wasnt all that painful

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A Word on Checklists

• Easy to create
• Easy to use
• Very simple way to prove compliance
• Dont need a mountain of paper

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Things I like

• Explanations of what the terms mean
• Examples of what might happen in reality
• Its less prescriptive than DO178B
• List of things which need to go in the plans
• The review checklists

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Things I dont like

• No top level document above HW SW
• No reference document to pull all the standards
  together
• No tables for process objectives or independence
• No FAQ
• The HC1 and HC2 categories
• The scope for over complication is endless

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Some Suggestions

• Create an on-line users forum
• Add an FAQ either to the document or on-line
• Add some tables for process objectives and
  independence as in DO178B
• Put a higher level explanatory document which
  knits together DO178B and DO254
• Provide guidance on which to use under which
  circumstances

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Questions