[theonewithin]

Mega doesn't have canbus support.

You would need to use serial3 as stated with it.

[dazq]

Dazq, thanks for the reply.
I hadn't really intended to use the Speeduino to control the data for the display, other than feed a data stream, hopefully CANbus. What I haven't discerned is if the mega is able to do that without a burden. The thought was to gen up a board for the Teensy that had the already included amps and add some buffers for the outputs similar to Pazi88's, or 4427's. It seems odd to me that someone hasn't already done that, and that leads me to believe I'm chasing ghosts. I'm going to regress a bit and just get a stock system sorted before I start adding frills.

Most people that move on to or need the features of a teensy or stm32 based speeduino usually use a custom all in one design rather than the adaptor,perhaps that's why it's not so popular..
I use an adaptor board for development,but have specific teensy boards for actual project builds.
A true full adaptor board I feel would be a nice and useful option especially if you could you it just generally as a replacement for a mega board in other projects not just speeduino.

There have been plenty of dashes and other displays connected using secondary serial ,those using can only do so usually (though not always) as the project car has it from OEM and needs integration.