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Build HAT Python library

License: MIT License

Python 100.00%

python-build-hat's Introduction

Build HAT

The Python Build HAT library supports the Raspberry Pi Build HAT, an add-on board for the Raspberry Pi computer, which allows control of up to four LEGO® TECHNIC™ motors and sensors included in the SPIKE™ Portfolio.

Hardware

The Build HAT provides four connectors for LEGO® Technic™ motors and sensors from the SPIKE™ Portfolio. The available sensors include a distance sensor, a colour sensor, and a versatile force sensor. The angular motors come in a range of sizes and include integrated encoders that can be queried to find their position.

The Build HAT fits all Raspberry Pi computers with a 40-pin GPIO header, including — with the addition of a ribbon cable or other extension device — Raspberry Pi 400. Connected LEGO® Technic™ devices can easily be controlled in Python, alongside standard Raspberry Pi accessories such as a camera module.

Documentation

Library documentation: https://buildhat.readthedocs.io

Hardware documentation: https://www.raspberrypi.com/documentation/accessories/build-hat.html

Projects and inspiration: https://projects.raspberrypi.org/en/pathways/lego-intro

Installation

To install the Build HAT library, enter the following commands in a terminal:

pip3 install buildhat

Usage

See the detailed documentation for the Python objects available.

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):
    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()

Building locally

Using asdf:

asdf install

Then:

pip3 install . --user

Building the documentation

Instructions for regenerating the documentation can be found in docs/README.md. Briefly, assuming you have the appropriate python modules installed:

$ (cd docs; make html)

will rebuild the documentation. The doc tree starts at docs/build/html/index.html

python-build-hat's People

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nstrijbosch simukdev mutesplash tomasz-lewicki rbbatista iwanimsand porchy13 andrewbuckingham tenderandshy duyaxiaruo jamsx highflying tomas-kubin per-oestergaard fransweb lurch caco3

python-build-hat's Issues

Look at exception produced when position set very frequently

build_hat.HubProtocolError: Unexpected reply to Output Goto Abs Position

Example that triggers issue:

from time import sleep
from build_hat import BuildHAT

bh = BuildHAT()
mouth_r = bh.port.C.motor
mouth_l = bh.port.D.motor

def move_mouth (l_pos,r_pos, speed=100):
    mouth_l.run_to_position(l_pos*-1,speed,blocking=False)
    mouth_r.run_to_position(r_pos,speed,blocking=False)

# Will crash after a while with
# build_hat.HubProtocolError: Unexpected reply to Output Goto Abs Position
while True:
    move_mouth(-20, -20)
    sleep(1)
    move_mouth(-45, -45)
    sleep(1)
    move_mouth(-45, -45)
    sleep(1)

Prevent multiple sensor instantiations from using the same port letter

e.g. prevent:

motor = Motor('A')
motor2 = Motor('A')

Run to position - keeps running continuously

Run to position, with a pair of motors seems to keep the motor running continuously for me

Investigate lighting up LEDs on distance sensor

Possible bug with setting motor position

Possible bug with setting motor position for both single motors and pair motors. If you run for rotations then set position it seems to go through more rotations than necessary to get to position

Bug: Make sleep lower, for 'get' function

Reduced sleep time from 1 second to 200 milliseconds.

Found that don't seem to get data in time with 100 milliseconds.

TODO: Create new exceptions to throw when necessary

Done for motor speed

Sometimes with a motor callback, the motor can oscillate between small position changes, do we want to filter those out?

Fixed with patch to firmware

TODO: Turn on/off notifications when callback is enabled or disabled

TODO: Set bias/plimit of motors in constant?

Partitioning of HSV colour space

Create N rotations function

Using existing rotation (to deg) function, create new function for N rotations

TODO: Store firmware/signature within Python library itself?

Test motor stalling

Test using:

bh.port.D.motor.run_for_degrees(3, 100)
bh.port.D.motor.run_for_degrees(201, 100)

TODO: Finish recursive descent style parser

TODO: Find correct hex sequence for 'write' command, to turn on colour sensor and ultrasonic sensor

HubProtocolError: Tx timeout

TODO: Implement function for setting non-combi modes

Simple modes can now be used.

Test moving multiple motors simultaneously

Motors can be paired doing:

pair = bh.port.D.motor.pair(bh.port.C.motor)

Conduct testing of different motor functions, such as:

pair.run_for_degrees(360, 20, 20)

TODO: motor when_rotated should only be called when motor position changed

Now perform simple check that motor angle has changed by a degree, before calling callback

Given an error message from the hat, it should provide the relevant port number

For single motor in Python code, call run to degrees rather than run for rotations, so it can take a float value

Callback for devices, such as force sensor etc.

Investigate short-range mode for distance sensor

Apply Rhodri's new patch for removing caching of motor data

The patch removes caching of motor data, so that you can still obtain the position of the motor
correctly after manual rotation.

Segmention fault using motor.pair in 0.2.5 but not an earlier version

Using master, get a segfault when running:

from build_hat import BuildHAT
bh = BuildHAT()
pair = bh.port.D.motor.pair(bh.port.C.motor)
pair.run_for_degrees(360, 20, 20)

But not when using commit:

git checkout 46e47b4e40cb29442d5a3d852bdc2135115ae9c1

TODO: function to let you change plimit/bias

TODO: Check if running bootloader or firmware in library and upload firmware if necessary etc.

TODO: Test what happens with library if run, without hat attached

TODO: Make system service to install firmware, requires firmware change to provide connected devices

ColorSensor implementation

Apply patch from Rhodri for 'detecting unresponsive hats'

Determine why Python is hanging at end of program, with wrapper

Look at exception produced when motor is physically prevented from turning - provide a clearer / more useful error message

Just tried this and got:

Traceback (most recent call last):
  File "motor.py", line 6, in <module>
    motor.run_for_rotations(10)
  File "/home/pi/.local/lib/python3.7/site-packages/build_hat-0.3.0-py3.7-linux-armv7l.egg/buildhat/motors.py", line 30, in run_for_rotations
    self._motor.run_for_rotations(rotations, self.default_speed)
build_hat.HubProtocolError: Motor stalled

Is that an ok message?

Bug: When you do start / stop motor for N seconds, then run_to_position, doesn't work correctly - Firmware

#!/usr/bin/python3

import time
from signal import pause
from buildhat import Motor

motor = Motor('A')
motor.set_default_speed(50)

def handle_motor(speed, pos, apos):
    print("Motor", speed, pos, apos)

motor.when_rotated = handle_motor

"""
When you do start / stop motor for N seconds, then run_to_position, doesn't work correctly
"""

print("Start motor")
motor.start()
time.sleep(3)
print("Stop motor")
motor.stop()
time.sleep(2)

print("Run to position 0")
motor.run_to_position(0)
time.sleep(3)

pause()

TODO: send 'off' for all motors when library exits

Add callback functionality for motors based on firmware modification in Python API

After modifying firmware, would need to add callback functionality in Python API

Need way to determine when hat is ready along with all sensors

In https://github.com/RaspberryPiFoundation/hub_module/blob/master/buildhat/devices.py currently
have a 'sleep' statement, which was necessary as sometimes the distance sensor wouldn't be detected without it.

Need to find a way to detect when a sensor is ready.

I notice in the following function there is also a delay present to: 'Give the HAT a chance to recognise what is attached to it'

Hub_init(HubObject *self, PyObject *args, PyObject *kwds)

The delay in this function could maybe be increased instead.

~~Implement turning on the motors for amount of time, in module, using new firmware feature~~
~~Implement motor pairs~~

from build_hat import BuildHAT
bh = BuildHAT()
bh.port.D.info()

Returns for a motor:

{'type': 49, 'fw_version': '0.0.0.1000', 'hw_version': '0.0.0.1000' ....

TODO: Need to be able to set stop state of motor - do through callback

Deadlock while closing hat

Thread 1:

#0  0xb6ed1a3c in __GI___pthread_timedjoin_ex (threadid=3050890336, thread_return=0x0, abstime=<optimized out>, 
    block=<optimized out>) at pthread_join_common.c:89
#1  0xb6597b48 in i2c_close_hat () at src/i2c.c:1127
#2  0xb659479c in Hub_finalize (self=<BuildHAT at remote 0xb65dcb38>) at src/hubmodule.c:231
#3  0x001589a0 in finalize_garbage (collectable=0xbeffa370, collectable@entry=0xbeffa368)
    at ../Modules/gcmodule.c:703
#4  0x0015976c in collect (generation=generation@entry=2, n_collected=n_collected@entry=0x0, 
    n_uncollectable=n_uncollectable@entry=0x0, nofail=nofail@entry=1) at ../Modules/gcmodule.c:905
#5  0x0015a300 in _PyGC_CollectNoFail () at ../Modules/gcmodule.c:1605
#6  0x00123518 in PyImport_Cleanup () at ../Python/import.c:526
#7  0x00132058 in Py_FinalizeEx () at ../Python/pylifecycle.c:1195
#8  0x00032fd4 in pymain_main (pymain=pymain@entry=0xbeffa418) at ../Modules/main.c:3040
#9  0x00033068 in _Py_UnixMain (argc=2, argv=0xbeffa5b4) at ../Modules/main.c:3073
#10 0x0002c268 in main (argc=<optimized out>, argv=<optimized out>) at ../Programs/python.c:15

Thread 2:

#0  __GI___poll (timeout=-1, nfds=1, fds=0xb658ee30) at ../sysdeps/unix/sysv/linux/poll.c:29
#1  __GI___poll (fds=0xb658ee30, nfds=1, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:26
#2  0xb65aa8d0 in get_callback (pitem=0xb658ee48) at src/callback.c:68
#3  0xb65aab04 in run_callbacks (arg=0x0) at src/callback.c:136
#4  0xb6ed0494 in start_thread (arg=0xb658f460) at pthread_create.c:486
#5  0xb6d3f578 in ?? () at ../sysdeps/unix/sysv/linux/arm/clone.S:73 from /lib/arm-linux-gnueabihf/libc.so.6
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 3:

#0  futex_abstimed_wait_cancelable (private=<optimized out>, abstime=0xb5d8dd80, expected=0, 
    futex_word=0x47b138 <_PyRuntime+720>) at ../sysdeps/unix/sysv/linux/futex-internal.h:205
#1  __pthread_cond_wait_common (abstime=0xb5d8dd80, mutex=0x0, cond=0x47b110 <_PyRuntime+680>)
    at pthread_cond_wait.c:539
#2  __pthread_cond_timedwait (cond=0x47b110 <_PyRuntime+680>, mutex=0x0, abstime=abstime@entry=0xb5d8dd80)
    at pthread_cond_wait.c:667
#3  0x000f9ac4 in PyCOND_TIMEDWAIT (us=<optimized out>, mut=<optimized out>, cond=<optimized out>)
    at ../Python/condvar.h:90
#4  take_gil (tstate=tstate@entry=0xb4c00650) at ../Python/ceval_gil.h:208
#5  0x000f9d8c in PyEval_RestoreThread (tstate=tstate@entry=0xb4c00650) at ../Python/ceval.c:271
#6  0x001349b4 in PyGILState_Ensure () at ../Python/pystate.c:1067
#7  0xb659e7ac in port_attach_port (port_id=1 '\001', type_id=62, hw_revision=0xb4c007f7 "", 
    fw_revision=0xb4c007fb "") at src/port.c:855
#8  0xb6596794 in handle_attached_io_message (buffer=0xb4c007f0 "\017", nbytes=15) at src/i2c.c:567
#9  0xb65971e4 in handle_immediate (buffer=0xb4c007f0 "\017", nbytes=15) at src/i2c.c:860
#10 0xb6597464 in run_comms_rx (args=0x0) at src/i2c.c:943
#11 0xb6ed0494 in start_thread (arg=0xb5d8e460) at pthread_create.c:486
#12 0xb6d3f578 in ?? () at ../sysdeps/unix/sysv/linux/arm/clone.S:73 from /lib/arm-linux-gnueabihf/libc.so.6
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

TODO: Remove delay for 'get' data function if possible, to improve speed

Now removed delay and used mutex which is unlocked when data received. Doesn't seem to have improved speed that much though.