Mega 2560 with RAMPS 1.4 for 4 axis

[ATAKASLA]

I am new to this site and just created a count yesterday. I am seeking help from the bioinformatics community. My project is to develop a kitchen microwave size automated RNA virus direct detection system. These viruses include HIV, Zika virus. In this system, I need to have 4 axis (X, Y, Z and A) independently controlled by Grbl. The A axis is to control defined liquid transfer in the system. I wanted to use Mega 2560 and RAMPS 1.4 for this project due to its compactness. This issue I currently have is the current Grbl 4 axis control firmware (Grbl8c1Mega2560) could not control the 4 axis via RAMPS 1.4. However, using codes (attached) directly uploaded to Mega2560/RAMPS 1.4 by IDE was able to drive all the five stepper motors connected to the RAMPS board. I wonder if someone could use this information to modify Grbl8c1Mega2560 to communicate with RAMPS 1.4. I don't write codes but I can test codes using what I have. Help is greatly appreciated.
XW
RAMPS 1.4-codes.docx