Hi loldavid6! Thanks for your message! 

Regarding your question, I'm using SPI to communicate between boards. I defined a very simple protocol that is currently working well. The COM module sends questions to other modules as integers, and they answer with data types, sizes and information. I do not know about UAVCAN, but will google it. 

SPI was selected as the backbone protocol because atmega328p is very cheap, well supported and has two SPIs when not running arduino code. I dedicated one of the SPIs to the bus and the other one to talk to the submodule. To use CAN instead of SPI I would have to change the micro controller.  As everything is modular, it can be done without problems, but will require us to design a new MCU module with a MCU that supports CAN and may require a change in the backbone connections. If you wish to help, it would be a very nice upgrade to the system. I can help you with that if necessary.

I can send you a kit of PCBs if you wish. You just pay for the cost of the boards and for the shipment. I can even send you the components too, but I'll have to calculate their cost. 

Thanks again for your message.

Hey, it been a while since I contacted you last, life caught up on me.  I love how your project has been progressing!  

Does you board use use UAVCAN?  If not would you at any point consider implementing it into your design?

Also, I would be interested in purchasing a panel.  

Keep up the good work!