manual_cnc.py

# Manually run a GCODE script on a Grbl CNC
# inspired  by https://github.com/Sam-Freitas/python_to_GRBL
# 
RAW_SCRIPT = '''
G21         ; Set units to millimeters
G90         ; Absolute positioning
G0 X0 Y0    ; Move to start point
M3 S1000
G1 Z-0.1 F100 ; Lower tool slightly (optional, depends on machine)
G1 X1 Y0 F200 ; Draw first edge
G1 X1 Y1      ; Second edge
G1 X0 Y1      ; Third edge
G1 X0 Y0      ; Close rectangle
G0 Z5        ; Lift tool
M5           ; Spindle off
M30          ; End program
'''
SCRIPT = ["G21", "G90", "G0 X0 Y0", "M3 S1000", "G1 Z-0.1 F100", "G1 X1 Y0 F200", "G1 X1 Y1", "G1 X0 Y1",
          "G1 X0 Y0", "G0 Z5", "M5", "M30"]


import serial
import time

def wait_idle(ser):
    while True:
        ser.reset_input_buffer()
        command = str.encode('?' + '\n')
        ser.write(command)
        grbl_out = ser.readline()

        if grbl_out.startswith(b"<Idle"):
            break
        else:
            time.sleep(0.1)


def send_command(ser, cmd: str):
    print(f"send: {cmd}")
    low_cmd = (cmd+"\n").encode()
    ser.write(low_cmd)
    wait_idle(ser) 
    out = ser.readline()
    print(f"ret: {out}")


s = serial.Serial("/dev/ttyUSB0", 115200, timeout=1)

for cmd in SCRIPT:
    send_command(s, cmd)