Extension: CNC Plotter

Contents

3.15. Extension: CNC Plotter#

In this extension project, you will program your Maqueen robot to create a simple drawing.

The Maqueen can hold a marker or large pen in its gripper. When the gripper holds the pen against a sheet of paper, the robot can draw by driving around on the page.

This program does not use sensors to follow a printed line. Instead, the robot follows movement instructions that you write in the code.

3.15.1. Instructions#

Open the MicroPython editor:

https://python.microbit.org/v/3

If you already have the editor open, use the existing window or tab.
Connect your micro:bit using the instructions from the previous page.
Enter the starter code below into the editor.

from microbit import *


def motor_left(speed, direction):
    buf = bytearray(3)
    buf[0] = 0x00
    buf[1] = direction
    buf[2] = speed
    i2c.write(0x10, buf)


def motor_right(speed, direction):
    buf = bytearray(3)
    buf[0] = 0x02
    buf[1] = direction
    buf[2] = speed
    i2c.write(0x10, buf)


def servo_one(angle=0):
    buf = bytearray(2)
    buf[0] = 0x14
    buf[1] = angle
    i2c.write(0x10, buf)


i2c.init()

# Startup sequence
while True:
    # Press button A to open the gripper and insert the pen
    if button_a.is_pressed():
        servo_one(100)
        sleep(500)

    # Press button B to close the gripper and begin drawing
    if button_b.is_pressed():
        servo_one(140)
        sleep(500)
        break

# Main loop - add your drawing code here
while True:
    sleep(1000)

Flash the code to your micro:bit.
Place the Maqueen on a sheet of paper with the pen touching the page.
Press button A to open the gripper and position the pen.
Press button B to close the gripper and start the drawing.

If you get stuck, ask a peer or your teacher for help.