Loads and starts executing a G-code program from a string containing G-Code commands.
start_code(gcode_string)
Start executing G-Code from a string
start_code("G21\nG0 X10 Y10\nM3\nG1 X50 Y50 F1000\nM5");
Start another G-Code program from a string
start_code("G90\nG0 Z5\nG1 X100 Y100 Z0 F500");