CSE 466 – Spring Introduction Implement Safety – Safe Software Language Features Type and Range Safe Systems Exception Handling Re-use, Encapsulation Objects Operating Systems Protocols Testing Regression Testing Exception Testing (Fault Seeding) Nuts and Bolts

CSE 466 – Spring Introduction - 2 Language Features  Type and Range Safe Systems: Pascal, Ada….Java? Program WontCompile1; type MySubRange = ; Day = {Mo, Tu, We, Th, Fr, Sa, Su}; var MyVar: MySubRange; MyDate: Day; begin MyVar := 9; {will not compile – range error} MyDate := 0; {will not compile – wrong type)  True type safety also requires runtime checking. a[j] := b; what must be checked here to guarantee type safety? range of j, range of b – this takes a lot of time!  Over head in time and code size. But safety may require this.  Does type-safe = safe?  If no, then what good is a type safe system?

CSE 466 – Spring Introduction - 3 Guidelines  Make it right before you make it fast  Verify during program execution  Pre-condition invariants  Things that must be true before you attempt to perform and operation.  Post-condition invariants  Things that must be true after and operation is performed  eg while (item!=tail) { process(item); if (item->next == null) { throw new CorruptListException(“Item” + item.id()); } else item = item->next; }  Exception handling What should happen in the event of an exception? who should be responsible for this check?

CSE 466 – Spring Introduction - 4 Exception Handling  Its NOT okay to just let the system crash if some operation fails! You must, at least, get into safe mode.  it is up to the designer to perform error checking on the value returned by f1 and f2. Easily put off, or ignored. Can’t distinguish error handling from not, no guarantee that all errors are handled gracefully.  a = f1(&b,&c) if (a) switch (a) { case 1: handle exception 1 case 2: handle exception 2 … } b = f2(&e,&f) if (a) switch (a) { case 1: handle exception 1 case 2: handle exception 2 … }

CSE 466 – Spring Introduction - 5 Exception Handling in Java void myMethod() throws FatalException { try { a = x.f1(&b,&c) b = x.f2(&e,&f) } catch (IOException e) { recover and continue } catch (ArrayOutOfBoundsException e) { not recoverable, throw new FatalException(“I’m Dead”); } finally { finish up and exit } Exceptions that are not handled will terminate the current procedure and raise the exception to the caller, and so on. Exceptions are subclassed so that you can have very general or very specific exception handlers. Separates throwing exceptions functional code exception handling

CSE 466 – Spring Introduction - 6 Safety of Object Oriented SW  Strongly typed at compile time  Run time checking is not native, but can be built into class libraries for extensive modularization and re-use. The class author can force the app to deal with exceptions by throwing them! class embeddedList extends embeddedObject() { public add(embeddedObject item) throws tooBigException { if (this.len() > this.max()) throw new tooBigException(“List size too big”); else addItem2List(); }  If you call embeddedList.add() you have three choices:  Catch the exception and handle it.  Catch the exception and map it into one of your exceptions by throwing an exception of a type declared in your own throws clause.  Declare the exception in your throws clause and let the exception pass through your method (although you might have a finally clause that cleans up first). Compiler will make you aware of any exceptions you forgot to consider!  When to use exceptions and when to use status codes or other means?

CSE 466 – Spring Introduction - 7 More Language Features  Garbage collection  What is this for  Is it good or bad for embedded systems  Inheritance  Means that type safe systems can still have functions that operate on generic objects.  Means that we can re-use commonalities between objects.  Encapsulation  Means the the creator of the data structure also gets to define how the data structure is accessed and used, and when it is used improperly.  Means that the data structure can change without changing the users of the data structure (is the queue an array or a linked list…who cares!)  Re-use  Use trusted systems that have been thoroughly tested  OS  Networking  etc.  Friday … how would Java be mapped to an embedded processor…say C++ to C51. What restrictions would you need to support that?

CSE 466 – Spring Introduction Testing  Unit test (white box)  requires knowledge of the detailed implementation of a single sub-system.  Test local functionality  Control algorithms  Boundary conditions and fault response  Integration Test (gray box)  Distributed processor systems w/ ongoing communications  Subsystems are already unit tested  Primarily for interfaces and component interaction  Falt seeding includes breaking the bus, disabling a subsystem, EMI exposure, power supply fluxuation, etc  Embedded systems require physical test environments  Validation Testing  Complete system  Environmental chamber  More fault seeding, bad user, etc.  Fault Seeding and Regression Testing!!!

CSE 466 – Spring Introduction Safe Design Process  Mainly, the hazard/risk/FMEA analysis is a process not an event!  How you do things is as important as what you do.  Standards for specification, documentation, design, review, and test  ISO9000 defines quality process…one quality level is stable and predictable.  There are many processes, but the good ones include release/test early and often! Incremental analysis, development, and testing

CSE 466 – Spring Introduction - 10 Interrupt v. Polling UController Seems to work, but hangs after first measurement. Why?

CSE 466 – Spring Introduction - 11 Closer Look The ‘ping’ is a series of 16 rapid clicks which requires rapid capacitor recharge Why do I bring this up under safety? UController

CSE 466 – Spring Introduction - 12 PCB Layout

CSE 466 – Spring Introduction - 13 PCB Layout

CSE 466 – Spring Introduction - 14 Critique  Good  Power distribution  Labeling  Compactness  Placement and Routing  Improve  Labeling (visible after stuffing)  Main power Caps (big and small).1uF 10uF  Crystal case grounding? (or oscillator instead of crystal, option?)  Space for extraction tool between cap and IC  4 mounting holes (standoffs)  Poor isolation of power circuits from logic circuits  Hole diameter for the power connector?

CSE 466 – Spring Introduction - 15 Friday  Friday  Embedded Java – think about multi-threading and synchronization  UML Example for Engine Controller  Demo: Air Trombone  Demo: Talk Application  Demo: Hi Fidelity