My company is designing the electronics for some UAV payloads and we are trying to decide on an inter-module serial comm scheme. Internally, we had chosen 485, but our customer asked why 485 and not ethernet, firewire, 1553, CAN, or USB. I am working on an answer for them and would like some input from this group.
We have some constraints on size, weight and shape because we will need to fit into leftover space inside unspecified packages. This makes me tend away from COTS plug-in-board solutions, which would make ethernet, USB, or 1553 simple to implement.
Our controllers for these modules will likely be from the AVR family - this is not set in stone but we already have experience with them and the tools. We don't expect to have huge amounts of data on this bus (it's mostly for command and status to a few sensors and motor controllers) and we don't currently know how many nodes we will need. The reason for having separate modules at all is to make it easier to adjust for feature creep and add new functionality without respinning every board when this happens.
I know there are some holes in this info and I will answer any questions that I can.
-- Joel Turner Mechtronic Solutions