Quote Originally Posted by hfjbuis View Post
That depends on your drivers. External drivers often have optocoupler inputs. If so, you probably can connect both mega boards to the same driver.
The mega2560 has onboard drivers without optocoupler inputs and unfortunately can't connect both mega boards to the same driver.
But I have not thought of that idea before, good one, thanks.

Quote Originally Posted by wyzarddoc View Post
It would not be a program "merge" as much as changing a lot of variables with a hardware switch and 1 long program
That's the idea. But is it possible?
I checked the mega2560 datasheet and it does not have programming SLOT's functionallity!
(Then it would have bin simply 2 seperate programs in 2 seperate slots without changing a lot of variables, also adding a hardware switch to select wich program to run.)
Mega2560 has a Flash memory of 256-8=248KB
* Marlin firmware is 120KB
* Gbrl firmware is 82KB?
It could fit in the chip. (And there are a lot of unused mega2560-pins for a selection hardware switch.)
In which code files of Marlin and Gbrl should the "changing a lot of variables" be done?