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Showing posts from September, 2013

Type punning, aliasing, unions, strict-aliasing, oh my!

Imagine that you have a struct s which sometimes needs to be volatile (because it maps to a set of hardware registers) but other times you'd rather have it non-volatile (because you are working on a bunch of such structs that have been stored, so they are no longer used to interface to the hardware and you could do without the performance penalty of volatile). That is easy enough: you can have your variables declared volatile or not depending on the situation. But what happens when you have a function to deal with those structs? Could it be implemented so it not only works, but does the right thing in both volatile and non-volatile structs? The trivial way to have such a thing is by just defining 2 versions of the function (with different names of course) with the differently qualified parameters; but another possibility is to define a union type in which one member is the plain type and the other is the volatile-qualified type, and make the function parameters use that

My first hardware bug report?

I have found what looks like a hardware bug in the AT90CAN128! I guess I could be happy in a geeky way, but the number of hours spent trying to track the problem make it a bit difficult :P. The thing is that aborting a pending MOb in the CAN controller embedded in the AT90CAN128 can leave CONMOB in an unexpected state. I am not totally sure if this is a hardware bug… or could be Atmel's library at90CANlib_3_2 being buggy AND misleading.

Atmel Studio 6 and blank Solution Explorer

Atmel Studio 6, which is (ununderstandably!*) based on Visual Studio (2010?), suddenly stopped showing anything in the Solution Explorer pane. The pane was there, it just remained empty, blank, apart from the "Properties" button (and the "Show all files" button shows up too, depending on the frontmost pane).