Should be written in C, not C++. Solvers we use are ODE solvers, and OMC exports an ODE interface. For QSS solvers, some additional information is needed. There used to be a code generator for this in OMC, but I am unsure of its current status.

Can you tell us a bit more about your solver? Did you implement it yourself? Or is it an adaption of an existing solver package? Is it a first-order or higher-order approach? ...
There are already some (experimental) qss implementations available/in development. So maybe it is possible to share some stuff in order to avoid too much redundant work.

The solver is an Linearly Explicit QSS solver that we are working on. We were planning on implementing this solver ourselves. I believe this solver would be an adaptation of the existing QSS with a second order approach. If we could collaborate on working on the existing QSS solver or creating and implenting a new solver, that would be much appreciated.

Is anyone aware of the QSS solvers (http://sourceforge.net/projects/qssengine/) by Joaquın Fernandez & Ernesto Kofman? They have a complete range of QSS solvers as well as 'n MicroModelica framework to utilise these solvers. Has there been any interaction between the development team at OpenModelica with the team working on MicroModelica?

Yes, we do collaborate with Federico Bergero in order to integrate their solver suite into OpenModelica. It is also planned to add a simcode target that directly exports code for their runtime system.
However, resources are quite limited and things don’t progress as fast as they should …

It would be good to join forces and work together on the existing qss implementation. Please feel free to comment on the current implementation or do pull requests in order to push modifications/extensions to the current approach.

Where can I find more information about how to export an ODE interface using OMC?

I googled it but I didn't find anything useful.

Is it readable file (e.g. XML)?

Thanks