Build HAT Python Library
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build-date: 2021-10-15
build-version: githash: 61115e7-dirty
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License
The Build HAT Python library is released under the MIT License.
Copyright (c) 2020-2021 Raspberry Pi Foundation
Copyright (c) 2017-2021 LEGO System A/S - Aastvej 1, 7190 Billund, DK
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Legal Disclaimer Notice 1
Build HAT Python Library
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License 2
Build HAT Python Library
Introduction
The Build HAT library has been created to support the Raspberry Pi Build HAT, an add-on board for the Raspberry Pi
computer which allows control of up to 4 LEGO® Technic™ motors and sensors included in the SPIKE™ Portfolio.
Figure 1. The
Raspberry Pi Build
HAT
Other LEGO® devices may be supported if they use the LPF2 connector:
Figure 2. The LEGO®
LPF2 connector
In order to drive motors, your Raspberry Pi and Build HAT will need an external 7.5v power supply. For best results, use the
official Raspberry Pi Build HAT power supply.
WARNING
The API for the Build HAT is undergoing active development and is subject to change. An online version of this
documentation can be found at https://buildhat.readthedocs.io/.
Introduction 3
Build HAT Python Library
Installation
The Python library can be installed using pip,
$ pip3 install buildhat-*.whl
Alternatively it can be cloned from its Github repositry,
$ git clone https://github.com/RaspberryPiFoundation/python-build-hat.git
$ cd python-build-hat
and installed. If using asdf first by,
$ asdf install
and then,
$ pip3 install . --user
Building the library,
$ ./build.sh
Installation 4
Build HAT Python Library
Usage
See the Library section for detailed documentation for the available Python objects.
import time
from signal import pause
from buildhat import Motor
motor = Motor('A')
motor.set_default_speed(30)
print("Position", motor.get_aposition())
def handle_motor(speed, pos, apos):
Ê print("Motor", speed, pos, apos)
motor.when_rotated = handle_motor
print("Run for degrees")
motor.run_for_degrees(360)
print("Run for seconds")
motor.run_for_seconds(5)
print("Run for rotations")
motor.run_for_rotations(2)
print("Start motor")
motor.start()
time.sleep(3)
print("Stop motor")
motor.stop()
pause()
Usage 5
Build HAT Python Library
Programming Bootloader
You can use openocd to program the bootloader. This can be installed by,
$ sudo apt install automake autoconf build-essential texinfo libtool libftdi-dev
libusb-1.0-0-dev
$ git clone https://github.com/raspberrypi/openocd.git --recursive --branch rp2040
--depth=1
$ cd openocd
$ ./bootstrap
$ ./configure --enable-ftdi --enable-sysfsgpio --enable-bcm2835gpio
$ make -j4
$ sudo make install
Then use the folloing command to program the bootloader
$ openocd -s /usr/local/share/openocd/scripts -f interface/raspberrypi-swd.cfg -f
target/rp2040.cfg -c "program bootloader.elf verify reset exit"
Programming Bootloader 6
Build HAT Python Library
Library
ColorSensor
The LEGO® Education SPIKE™ Colour Sensor (LEGO® Colour Sensor 45605) can sort between 8 different colours and can
measure reflected and ambient or natural light.
Ê1 from buildhat import ColorSensor
Ê2
Ê3 color = ColorSensor('C')
Ê4
Ê5 print("HSV", color.get_color_hsv())
Ê6 print("RGBI", color.get_color_rgbi())
Ê7 print("Ambient", color.get_ambient_light())
Ê8 print("Reflected", color.get_reflected_light())
Ê9 print("Color", color.get_color())
10
11 print("Waiting for color black")
12 color.wait_until_color("black")
13 print("Found color black")
14
15 print("Waiting for color white")
16 color.wait_until_color("white")
17 print("Found color white")
18
19 while True:
20 c = color.wait_for_new_color()
21 print("Found new color", c)
ColorDistanceSensor
Ê1 from buildhat import ColorDistanceSensor
Ê2
Ê3 color = ColorDistanceSensor('C')
Ê4
Ê5 print("RGBI", color.get_color_rgb())
Ê6 print("Ambient", color.get_ambient_light())
Ê7 print("Reflected", color.get_reflected_light())
Ê8 print("Color", color.get_color())
Ê9
10 print("Waiting for color black")
11 color.wait_until_color("black")
12 print("Found color black")
13
14 print("Waiting for color white")
15 color.wait_until_color("white")
16 print("Found color white")
ColorSensor 7
Build HAT Python Library
17
18 while True:
19 c = color.wait_for_new_color()
20 print("Found new color", c)
DistanceSensor
The LEGO® Education SPIKE™ Distance Sensor (LEGO® Distance Sensor 45604) behaves like a conventional ultrasonic
range finder but also has 4 LEDs that can be used to create the “eyes” of a robot. Each LED can be controlled individually.
Ê1 from signal import pause
Ê2 from buildhat import Motor, DistanceSensor
Ê3
Ê4 motor = Motor('A')
Ê5 dist = DistanceSensor('D', threshold_distance=100)
Ê6
Ê7 print("Wait for in range")
Ê8 dist.wait_for_in_range(50)
Ê9 motor.run_for_rotations(1)
10
11 print("Wait for out of range")
12 dist.wait_for_out_of_range(100)
13 motor.run_for_rotations(2)
14
15 def handle_in(distance):
16 print("in range", distance)
17
18 def handle_out(distance):
19 print("out of range", distance)
20
21 dist.when_in_range = handle_in
22 dist.when_out_of_range = handle_out
23 pause()
ForceSensor
The LEGO® Education SPIKE™ Prime Force Sensor (LEGO® Force Sensor Set 45606e) can measure pressure of up to 10
Newtons, but it can also be used as a touch sensor or a simple button.
NOTE
The Prime Force Sensor is also know as the LEGO® Technic Force Sensor.
Ê1 from signal import pause
Ê2 from buildhat import Motor, ForceSensor
Ê3
Ê4 motor = Motor('A')
Ê5 button = ForceSensor('D', threshold_force=1)
DistanceSensor 8
Build HAT Python Library
Ê6
Ê7 print("Waiting for button to be pressed fully and released")
Ê8
Ê9 button.wait_until_pressed(100)
10 button.wait_until_released(0)
11
12 motor.run_for_rotations(1)
13
14 print("Wait for button to be pressed")
15
16 button.wait_until_pressed()
17 motor.run_for_rotations(2)
18
19 def handle_pressed(force):
20 print("pressed", force)
21
22 def handle_released(force):
23 print("released", force)
24
25 button.when_pressed = handle_pressed
26 button.when_released = handle_released
27 pause()
Matrix
The Spike 3x3 LED matrix has individual elements that can be set individually or as a whole.
Number Name
0
1 pink
2 lilac
3 blue
4 cyan
5 turquoise
6 green
7 yellow
8 orange
9 red
NOTE
Colours may be passed as string or integer parameters.
Ê1 from buildhat import Matrix
Ê2 import time
Ê3 import random
Matrix 9
Build HAT Python Library
Ê4
Ê5 matrix = Matrix('C')
Ê6
Ê7 matrix.clear(("red",10))
Ê8 time.sleep(1)
Ê9
10 matrix.clear()
11 time.sleep(1)
12
13 matrix.set_pixel((0,0), ("blue", 10))
14 matrix.set_pixel((2,2), ("red", 10))
15 time.sleep(1)
16
17 while True:
18 out = [[(int(random.uniform(0,9)),10) for x in range(3)] for y in range(3)]
19 matrix.set_pixels(out)
20 time.sleep(0.1)
Motor
Motors from the LEGO® Education SPIKE™ portfolio (LEGO® Large angular motor 45602 and LEGO® Medium angular
motor 45603) have an integrated rotation sensor (encoder) and can be positioned 1-degree accuracy. The encoders which
can be queried to find the current position of the motor with respect to a ‘zero’ mark shown on the motor itself. Other
motors without encodes will report a 0 value if queried.
Ê1 from signal import pause
Ê2 from buildhat import Motor
Ê3 import time
Ê4
Ê5 motor = Motor('A')
Ê6 motorb = Motor('B')
Ê7
Ê8 def handle_motor(speed, pos, apos):
Ê9 print("Motor", speed, pos, apos)
10
11 motor.when_rotated = handle_motor
12 motor.set_default_speed(50)
13
14 print("Run for degrees 360")
15 motor.run_for_degrees(360)
16 time.sleep(3)
17
18 print("Run for degrees -360")
19 motor.run_for_degrees(-360)
20 time.sleep(3)
21
22 print("Start motor")
23 motor.start()
24 time.sleep(3)
25 print("Stop motor")
26 motor.stop()
27 time.sleep(1)
Motor 10
Build HAT Python Library
28
29 print("Run for degrees - 180")
30 motor.run_for_degrees(180)
31 time.sleep(3)
32
33 print("Run for degrees - 90")
34 motor.run_for_degrees(90)
35 time.sleep(3)
36
37 print("Run for rotations - 2")
38 motor.run_for_rotations(2)
39 time.sleep(3)
40
41 print("Run for seconds - 5")
42 motor.run_for_seconds(5)
43 time.sleep(3)
44
45 print("Run both")
46 motor.run_for_seconds(5, blocking=False)
47 motorb.run_for_seconds(5, blocking=False)
48 time.sleep(10)
49
50 print("Run to position -90")
51 motor.run_to_position(-90)
52 time.sleep(3)
53
54 print("Run to position 90")
55 motor.run_to_position(90)
56 time.sleep(3)
57
58 print("Run to position 180")
59 motor.run_to_position(180)
60 time.sleep(3)
MotorPair
1 from buildhat import MotorPair
2
3 pair = MotorPair('C', 'D')
4 pair.set_default_speed(20)
5 pair.run_for_rotations(2)
6
7 pair.run_for_rotations(1, speedl=100, speedr=20)
8
9 pair.run_to_position(20, 100, speed=20)
MotorPair 11
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