Not directly but if you have .a lib files you can put them in a \libs folder below the project. They will then be included in the link. Does this help?

Thanks, this is very useful info and discussion. It would be good to achieve but possibly not practical, I don't want you to waste your time. Here is some info anyway.

Firstly, a lib folder can be created by you directly below each project folder. Myproj\Libs. Placing .a files in this folder will cause them to be linked. Adding them also to the AS7 projectName > "Libraries" node in the solution explorer will also allow atmel intellisense to use them. (It would be nice if visual micro could simply use the "Libraries" node but unfortenatly atmel pre-adds libs to the node which users don't expect. Therefore the "Libraries" node is just to help intellisense and does not affect compile. Only the extra files in project\Libs are linked)

To add files to an arduino project they must exist in the project folder or the project\src folder or any folder below the project\src folder.

Normally arduino projects use a main.cpp which exists in the platform core. If you add a main.cpp to your project folder then visual micro will use the local one instead of the one in the core. That's a main.cpp not a main.c which might be a problem for you.

To see the original main.cpp for your current core you can click "vMicro>Show hiden files". You will see the main.cpp is responsible for startup and calls your setup() and loop() in your .ino code. You need to copy the main.cpp contents into your new local main.cpp override otherwise your .ino code won't work.

After you have finished reviewing the original main.cpp you can delete the short cuts that Visual Micro added to your project or click the "vMicro>Show hidden files" command again and it will delete them for you. The shortcuts added by that command cause no harm and do not affect compilation but might slow the ide down especially if you frequently switch between different boards in the same project.

Having access to the main.cpp is the closest you get to overriding arduino without breaking it and without creating your own custom core.

I hope this makes sense?

Only .a files in lib.

Normal sources need to be in the project within the "legal" folders I mentioned (pro, src, src/....." or made into Arduino compatible libraries. Arduino compatibile libraries simply means getting the right folder structure

MyLibraries\Lib1\library.properties
MyLibraries\Lib1\src

MyProject\Proj1\Proj1.ino
MyProject\Proj1\src


Libraries can exist anyware but outside of the project folder. Use the visual micro examples in file>new>project area to see how things work.

Thanks for the update. I agree with everything that you have said.

Yes digitalWrite is slow but it is portable which makes it possible to upgrade or switch mcu without code changes. All other speedy solutions appear to be architecure dependant.

One lame solution but an improvement: If you look at what the arduino does for digital write I suspect that you can by pass some of their code quite easily. One obvious overhead if when we use digitalWrite(13, HIGH) the 13 first has to be resolved to the read port/pin for the current board. If you wanted to hard code these values I am sure you could then call whatever digitalWrite() calls but without the pin resolver. That would probably speeds things up a lot (but digitalWrite() was just one  example that you made, I know that!