I'm doing a project for college connecting an app made with app inventor to a Raspberry Pi and then using the RPi to make a printing queue for a Prusa P3 Steel.

The thing is that I already have the comm between the app and the RPi but I need to connect the RPi to the Arduino via USB and select the G-code files that are in the SD card of the Prusa to print. I don't know where should I put the function in the Marlin code or how to manage the serial port read function.

Any ideas?

  • $\begingroup$ why don't you connect the prusa via USB to the Rpi? That way you can feed the G-code directly and keep the queue on the Pi. $\endgroup$
    – Hacky
    Dec 27, 2017 at 13:30
  • $\begingroup$ Just out of interest: Are you using MIT App Inventor for iOS or App Inventor for Android? $\endgroup$
    – Greenonline
    Oct 9, 2018 at 17:49

1 Answer 1


You can send the G Codes to select and print a file over the serial connection.

  • List the files


  • Select a file name

    M23 filename.gco

  • Start/Resue the print


See https://reprap.org/wiki/G-code for more information M20 through M39 are the ones for interfacing with SD Card files.


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