Send G-Code to Arduino Mega (Marlin 1.1.0-RC7)

Hello to all Programmers,

I am currently writing on my Bachelor Thesis and I need to send g-code (generated in LabView) from Labview to an Arduino Mega (of a 3D-Printer), where Marlin 1.1.0-RC7 is running.

Usually the g-code is sent from RepetierHost via Serial Connection to the Arduino (which works perfectly), now I want to do it from LabView directly.

I have installed the VISA Library for Labview and when I send through the serial Connection a g-code (M42 P57 S255 meaning: turn on Pin 57) I only get Information as for the Printer set up, but it is not answering my command, meaning the pin is not going on, even though through RepetierHost it is (-->pic Visa Test).

Then a lecturer advised me to add a carriage return, an empty string or a \n (next line) after my command. There came the same Printer-Infos, but when I put the carriage return in front of the command, there was showing:

echo: Unknown command: ""

ok

above the same usual lines that were showing in the tests before (-->pic/vi Visa Test 2):

start

echo: External Reset

Marlin 1.1.0-RC7

echo: Last Uploaded…

and no Pin is lit.

Are there maybe other elements I have to put before or after my command?

I would be extremely thankful, if you could give me some advice.

Best regards,

Lea