Turtle Graphics on Gizmo

Libraries

Now we'll install the libraries that we need to use Turtle graphics on the Circuit Playground Bluefruit with TFT Gizmo.

Click this link to go to the circuitpython.org Libraries page. Download the latest version of the Bundle library .zip file that matches the version of CircuitPython you're using on the board.

Uncompress the .zip file and then copy the following directory and three library .mpy files to the lib directory of the CIRCUITPY drive:

  • adafruit_bus_device
  • adafruit_logging.mpy
  • adafruit_st7789.mpy
  • adafruit_turtle.mpy

The Mu Editor

Adafruit recommends using the free program Mu to edit your CircuitPython programs and save them on your Circuit Playground Bluefruit. You can use any text editor, but Mu has some handy features.

See this page on the Circuit Playground Bluefruit guide on the steps used to install Mu.

Turtle Graphics Code

Let's start of with a simple bit of code. It will draw a square on the screen.

Copy the code below and then paste it into a new document in Mu. Save it to the CIRCUITPY drive as code.py.

#Turtle Gizmo Square
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

turtle.pendown()

#top
turtle.forward(80)
turtle.right(90)

#right
turtle.forward(80)
turtle.right(90)

#bottom
turtle.forward(80)
turtle.right(90)

#left
turtle.forward(80)
turtle.right(90)

while True:
    pass

Square

After the setup code imports libraries and configures some pins for the display, the main body of the code runs. Watch the screen on your TFT Gizmo as the board restarts and runs the code.

First, it sets the pen down with the turtle.pendown() command. (Later, you'll learn to lift the pen with turtle.penup() so you don't always draw a line then the turtle moves!)

The turtle starts out at the origin point -- 0,0 on the x- and y-axis respectively. It then moves forward 80 pixels, drawing a line as it goes using the turtle.forward(80) command. This draws the top of the square.

Next, the turtle turns right using the turtle.right(90) command.

This same pair of commands -- forward() and right() -- run three more times in order to complete the square.

Since there are some repetitive steps in there, we can tidy up the code by iterating through a loop four times like this:

#Turtle Gizmo Square Loop
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

turtle.pendown()
for _ in range(4):
    turtle.forward(80)
    turtle.right(90)

while True:
    pass

Try out that code -- it's much shorter, but you'll see the same square drawn on the screen!

Asterisk

Now that we can loop through a command many times, let's add another two commands -- turtle.back()and turtle.left()

We can move forward and backward to create a line, shift the angle 18 degrees to the left, and do it all again. After twenty iterations of this we have a nice star pattern!

With a small change to the code (see the comment on line 18) we can turn this into an iris pattern!

#Turtle Gizmo Asterix
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

turtle.pendown()
for _ in range(20):
    turtle.forward(80)
    turtle.back(80) #try changing this to 70 for an iris effect
    turtle.left(18)

while True:
    pass

Circle

The built-in command turtle.circle() makes it very simple to draw a triangle. No, just kidding! It draws a circle!

Try out the example here, and then us some different numbers for the circle radius instead of the 118 here.

# Turtle Gizmo Circle
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

turtle.penup()
turtle.right(90)
turtle.forward(118)
turtle.left(90)
turtle.pendown()
turtle.circle(118) #radius of the circle

while True:
    pass

Circle Petals

Let's get a little fancy. We will now introduce a few more techniques, including the turtle.pencolor() command to change the color of the line that our turtle draws, as well as iterating through multiple loops with changing variables.

This will allow us to change the size of a series of five circles, and repeat the pattern four times.

# Turtle Circle Petals
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import Color, turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

colors = [Color.YELLOW, Color.GREEN]

for _ in range(4):
    for i in range (5):
        turtle.pencolor(colors[i % 2])
        turtle.pendown()
        turtle.circle(60 - (i*10) )
        turtle.penup()
    turtle.right(90)

while True:
    pass

Star

Here's a super stylish, 1970's inspired star! Note how the length of each forward command is increased as the value of i goes up during each of the 26 iterations of the loop.

# Turtle Gizmo Star Fancy
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import Color, turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

turtle.pendown()
turtle.pencolor(Color.BLUE)
for i in range(26):
    turtle.fd(i*10)
    turtle.rt(144)

while True:
    pass

Rainbow Benzene

Here's a classic, beautiful design. This hexagonal shape twists with each iteration, and every side of each perceived hexagon is a different color of the rainbow!

# Turtle Gizmo Rainbow Benzene
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import Color, turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

benzsize = min(display.width, display.height) * 0.5

print("Turtle time! Lets draw a rainbow benzene")

colors = (Color.RED, Color.ORANGE, Color.YELLOW, Color.GREEN, Color.BLUE, Color.PURPLE)

turtle.pendown()
start = turtle.pos()

for x in range(benzsize):
    turtle.pencolor(colors[x%6])
    turtle.forward(x)
    turtle.left(59)

while True:
    pass

Parabolas

This lovely parabolic curve set creates the illusion of curvature. It is in fact made up entirely of straight line segments, just as you would with a piece of string art and some pins pushed into a canvas.

It also introduces the turtle.dot() command, which drops down a dot of your desired radius wherever the turtle is. In this case, the turtle is moved with turtle.goto() This command allows the turtle to instantly head to a coordinate point on the screen rather than needing explicit angle rotations specified along with a "forward" command.

# Turtle Gizmo Parabolic Jack
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import Color, turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

print("Draw parabolas using straight line segments!")

def vert(x, y, size):
    turtle.goto(x, y)
    turtle.dot(size)

turtle.penup()
turtle.pencolor(Color.GREEN)

vert(0, 0, 7)
vert(0, 100, 7)
vert(100, 0, 7)
vert(0, -100, 7)
vert(-100, 0, 7)

x_quad=[10, 10, -10, -10]
y_quad=[10, -10, -10, 10]

for q in range(4):
    for i in range(0,11):
        x_from = 0
        y_from = (10-i) * y_quad[q]
        x_to = i * x_quad[q]
        y_to = 0
        turtle.penup()
        turtle.goto(x_from,y_from)
        turtle.pendown()
        turtle.goto(x_to,y_to)

turtle.home()


while True:
    pass

Sierpinski Triangle

Time to get fractal! These are recursive, equilateral triangles as described by Waclaw Sierpinski in 1915! Read more about them here.

# Turtle Gizmo Sierpinski Triangle
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

def getMid(p1, p2):
    return ((p1[0] + p2[0]) / 2, (p1[1] + p2[1]) / 2) #find midpoint

def triangle(points, depth):

    turtle.penup()
    turtle.goto(points[0][0], points[0][1])
    turtle.pendown()
    turtle.goto(points[1][0], points[1][1])
    turtle.goto(points[2][0], points[2][1])
    turtle.goto(points[0][0], points[0][1])

    if depth > 0:
        triangle([points[0],
                  getMid(points[0], points[1]),
                  getMid(points[0], points[2])],
                 depth-1)
        triangle([points[1],
                  getMid(points[0], points[1]),
                  getMid(points[1], points[2])],
                 depth-1)
        triangle([points[2],
                  getMid(points[2], points[1]),
                  getMid(points[0], points[2])],
                 depth-1)

big = min(display.width/2, display.height/2)
little = big / 1.4
seed_points = [[-big, -little], [0, big], [big, -little]] #size of triangle
triangle(seed_points, 4)

while True:
    pass

Hilbert Curve

Here's another interesting fractal pattern, called a Hilbert curve.

# Turtle Gizmo Hilbert
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import Color, turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

def hilbert2(step, rule, angle, depth, t):
    if depth > 0:
        a = lambda: hilbert2(step, "a", angle, depth - 1, t)
        b = lambda: hilbert2(step, "b", angle, depth - 1, t)
        left = lambda: t.left(angle)
        right = lambda: t.right(angle)
        forward = lambda: t.forward(step)
        if rule == "a":
            left()
            b()
            forward()
            right()
            a()
            forward()
            a()
            right()
            forward()
            b()
            left()
        if rule == "b":
            right()
            a()
            forward()
            left()
            b()
            forward()
            b()
            left()
            forward()
            a()
            right()

turtle.penup()

turtle.goto(-108, -108)
turtle.pendown()
turtle.pencolor(Color.PURPLE)
hilbert2(7, "a", 90, 5, turtle)

while True:
    pass

Koch Snowflake

This is a third generation fractal Koch snowflake.

# Turtle Gizmo Koch Snowflake
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

def f(side_length, depth, generation):
    if depth == 0:
        side = turtle.forward(side_length)
    else:
        side = lambda: f(side_length / 3, depth - 1, generation + 1)
        side()
        turtle.left(60)
        side()
        turtle.right(120)
        side()
        turtle.left(60)
        side()

turtle.penup()
turtle.goto(-99, 56)
turtle.pendown()

num_generations = 3
top_side = lambda: f(218, num_generations, 0)

top_side()
turtle.right(120)
top_side()
turtle.right(120)
top_side()

while True:
    pass

Christmas Tree

This lovely Christmas tree was adapted from this program written by Keith Randall.

# Turtle Gizmo Christmas Tree
#==| Turtle Gizmo Setup start |========================================
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import Color, turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

# Fractal Christmas Tree:
# https://codegolf.stackexchange.com/questions/15860/make-a-scalable-christmas-tree
#  by Keith Randall
n = 42  # input value for scaling the tree. note: ornaments don't scale
turtle.goto(0, -20)

#star
turtle.left(90)
turtle.forward(3*n)
turtle.pencolor(Color.YELLOW)
turtle.left(126)
turtle.pendown()
for _ in range(5):
    turtle.forward(n/5)
    turtle.right(144)
    turtle.forward(n/5)
    turtle.left(72)
turtle.right(126)

#tree
turtle.pencolor(Color.GREEN)
turtle.back(n*4.8)

def tree(d,s):
    if d <= 0:
        return
    turtle.forward(s)
    tree(d-1, s*.8)
    turtle.right(120)
    tree(d-3, s*.5)
    turtle.right(120)
    tree(d-3, s*.5)
    turtle.right(120)
    turtle.back(s)
turtle.pendown()
turtle.pencolor(Color.GREEN)
tree(15, n)
turtle.back(n/2)

#ornaments
def ornament(x, y):
    turtle.penup()
    turtle.goto(x, y)
    turtle.pencolor(Color.RED)
    turtle.pendown()
    turtle.dot(7)
    turtle.penup()

orn_pnts=[  (5, 60), (-7, 40), (10, 20), (-15, 0), (25, -20),
            (-27, -30), (7, -33), (40, -60), (-9, -63),
            (-50, -88), (62, -97) ]

for j in range(len(orn_pnts)):
    ornament(orn_pnts[j][0], orn_pnts[j][1])


turtle.penup()
turtle.goto(0, -120)

while True:
    pass

Snowflakes

This example will draw lots of beautiful snowflake-style patterns! If you want to get technical about the number of sides in your flakes, make some adjustments to this line:

draw_flake(randint(5, 8)) #adjust number of arms here

# Turtle Gizmo Snowflakes
#==| Turtle Gizmo Setup start |========================================
import time
from random import randint
import board
import busio
import displayio
from adafruit_st7789 import ST7789
from adafruit_turtle import turtle
displayio.release_displays()
spi = busio.SPI(board.SCL, MOSI=board.SDA)
display_bus = displayio.FourWire(spi, command=board.TX, chip_select=board.RX)
display = ST7789(display_bus, width=240, height=240, rowstart=80,
                 backlight_pin=board.A3, rotation=180)
turtle = turtle(display)
#==| Turtle Gizmo Setup end |=========================================

def draw_arm():
    turtle.pendown()
    for angle, length in arm_data:
        turtle.forward(length)
        turtle.left(angle)
        turtle.forward(length)
        turtle.backward(length)
        turtle.right(2*angle)
        turtle.forward(length)
        turtle.backward(length)
        turtle.left(angle)
    turtle.penup()

def draw_flake(arms):
    turtle.penup()
    turtle.home()
    turtle.clear()
    angle = 0
    delta_angle = 360 // arms
    for _ in range(arms):
        turtle.home()
        turtle.setheading(angle)
        draw_arm()
        angle += delta_angle
    turtle.penup()
    turtle.home()

while True:
    arm_data = [(randint(30, 80), randint(10, 40)) for _ in range(5)]
    draw_flake(randint(5, 8)) #adjust number of arms here
    time.sleep(5)

Where to Find More

You can find much more information about turtle graphics as well as example scripts through an Internet search of "turtle python graphics examples" or some variation. Since turtle graphics are mainly in terms of moving and turning they can usually be converted to CircuitPython and the adafruit_turtle library.

Check out these example sites:

This guide was first published on Nov 05, 2019. It was last updated on Nov 05, 2019. This page (Turtle Graphics on Gizmo) was last updated on Nov 12, 2019.