Quick guide

To get your Arduino to control a plotter, following steps are needed:

Windows USB driver

Connect your Arduino with your PC, on windows 10 the needed USB driver will be installed automatically, if not: the cheap Arduino clones often uses a CH340 chip. Check here for more information https://www.google.de/search?q=arduino+ch340.

Grbl firmware

Download and unzip GRBL-Plotter. Start the program XLoader.exe. Select the desired firmware, correct device and the correct com port, then upload the firmware. With the shown settings, the upload took 18 seconds.

grbl_v1.1h.20190825.hex is the latest regular grbl firmware for Arduino uno and nano, from https://github.com/gnea/grbl
grbl_v1.1f_Servo.hex as above, but with Spindle-PWM adapted to RC-Servo specification (1ms - 2ms), from https://github.com/cprezzi/grbl-servo
grbl-Mega-5X-v1.1l.20190605.hex 5 axis version for Arduino Mega2560 only, from https://github.com/fra589/grbl-Mega-5X

After successful upload, close XLoader and reset the controller.

1st connection

Install GRBL-Plotter by starting 'setup.exe' from the unzipped folder. Start GRBL-Plotter and select the correct COM-port for the controller. After successful connection, grbl sends a start-up message "Grbl 1.1h ['$' for help]".

Now the buttons inside the GUI are enabled and the stepper motors can be controlled.

Configuration of grbl

After pressing "$$", grbl lists the stepper motor settings, which must be adapted for each machine. Check the grbl-Wiki for more information. The screenshoot shows the initial settings after the installation of grbl.

The main settings are $3, $10x, $11x (x=0,1 or 2 depending on axis) to get the stepper motors running in the correct direction. The correct direction means:

+X = to the right
+Y = to the back
+Z = upwards

Note: a too large number for $10x (steps/mm) and $11x (max. speed) will cause problems.
The product of $10x and $11x must stay below 1800000 to avoid pin frequencies above 30 kHz.
E.g. $100=250, $110 = 7200 is at the edge.