# Error: 20, non stop, while connected to Pronterface: no G-code uploaded yet

I am trying to make a pen plotter from scratch. I hooked up two scanners to form X and Y axis, and using a CD drive to lift the pen. I connected everything to Arduino Mega 2560 and RAMPS 1.4 shield with DRV8825 drivers. I tested everything using simple Arduino sketches that sent step signals. So far, so good, however, today I uploaded GRBL and downloaded Pronterface, to actually use G-code, but after successfully connecting on Pronterface to the port at the 115200 Baud rate, I am only getting error: 20 non stop.

• Hi welcome to 3DPrinting.SE! Note that error 20 notifies you of an incorrectly sent G-code instruction. Are you sure Pronterface isn't sending constantly ( e.g. to probe for temperatures) while GBRL doesn't support the G-code? – 0scar Feb 17 at 18:27
• I am sooooo sorry, that I am replying today after 4 days passed. My internet connection was not working. About the question here is that: even if pronterface is sending some unsupported g code, the basic +1, +10, +100 mm movements for X and Y should work. This got mpre confusing when I uploaded Marlin instead of GRBL, everything started to work perfectly. But when I switched back to GRBL, nothing was working again! And sorry, once again for such a late reply. – Yahya Feb 20 at 19:19
• I think Pronterface is sending M105 to probe the temperatures of hotend and bed. GBRL doesn't support that. As it is periodically sent, the program reports an error, you cannot use this program for movement while it already is in error. – 0scar Feb 20 at 21:03