How download and refirmware
Download REFIRMWARE.ZIP from https://sites.google.com/site/esp12wifi/refirmware-grbl-modified/refirmware.zip, unzip folder connect with usb cable your pc with arduino and execute GRBL_PD2_PC0.bat
Come caricare programma grbl modificato in arduino
Scarica REFIRMWARE.ZIP da qui https://sites.google.com/site/esp12wifi/refirmware-grbl-modified/refirmware.zip, decomprimere la cartellaconnetti con cavo usb tuo pc con scheda arduino e eseguire GRBL_PD2_PC0.bat