Embedded

Unboxing the new RTBx

Christmas came early at Rapita this year with the unboxing of the new RTBx 2220 datalogger.
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What happened first? Handling timer wraparound

Suppose you had to determine which of two timestamps occurred first. Clearly the “obvious“ approach is to use a simple numerical comparison, for example:
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Function pointers and their impact on stack analysis

Function pointers present a real problem for static code analysis, including when calculating stack usage. Understanding software stack requirements is an activity that is required for several standards/guidelines including DO-178B and DO-178C. Nevertheless function pointers are supported and therefore prevalent in most system-level languages (C and Ada both have them, whilst they are used all the time with C++).
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Optimising for code size might not do what you expect - a GCC and PowerPC example

Getting tracing libraries to run on a new system is hard, but it's something that we regularly have to do here at Rapita as part of our support for timing analysis on diverse platforms. In the past few weeks I've been experimenting with creating a tracing library for Freescale's P4080DS development board, which comes fully loaded with an 8 core P4080 SoC and plenty of trace options, including Aurora based NEXUS tracing, multiple ethernet links and lots of DRAM.
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Lesser used PowerPC instructions

We've been looking recently at some object code from an Ada compiler for the PowerPC e500v2 core. As part of this, we examined the distribution of instruction mnemonics in the code generated by this particular use of the compiler on a suite of example programs. The split by type of instruction is roughly as follows: Interestingly, there aren't as many compare operations as we might otherwise expect. This is because xor tends to be used for this instead
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