So I downloaded and unzipped the dual firmware: 2 Questions.
There are two files on GITHUB. There is a V1CNC_Rambo_Dual and a V1CNC_Rambo_DualLR. What is the difference?
Also - Instructions say that I should upload the Marlin.INO file. THis files does not seem to be there. There is a MARLIN file that shows up as an Arduino file and the directory looks almost identical to the one in the documentation but it does not seem to be the right file. Which one should I download and where is the INO file?
V1CNC_Rambo_Dual: This is the firmware for the Primo, assuming dual endstops. 2 drives + endstops for X, 2 drives + endstops for Y, 1 drive + touch plate for Z.
V1CNC_Rambo_DualLR: This is the firmware for the LowRider2, assuming dual endstops. 2 drives + endstops for Y, 2 drives + endstops + touchplate for Z, 1 drive + endstop for X.
The difference is the extra drive for Z and one less drive for X, since the LR2 needs the extra Z motor, and people don’t use the optional extra X drive.
As Dan indicates, if you are building a dual endstop version of the LowRider, then you want the DualLR version of the firmware. Due to the size and complexity of the Marlin builds these days, getting the project to compile in the Arduino IDE is problematic. Instead the recommended pathway is to use Platform IO, and is documented here. If you want to try using the Arduino IDE, then the file you are looking for is Marlin/Marlin/Marlin.ino
There is an alternate, no-compile way to upload the firmware that I explain in this post. Since making that post, the binary file has been moved to the top (inside first ZIP file) and is called firmeware.hex.