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SweepPy

Python Scanse Sweep LiDAR library. Work with Python2 and Python3.

Requires libsweep.so to be installed.

Installation

Install sweeppy module for Python3 locally:

python3 setup.py install --user

Example for testing

In the following, replace /dev/ttyUSB0 with your device's port name. This executes __main__.py (also works without the installation step).

python -m sweeppy /dev/ttyUSB0

See app.py for the common use-case where you have to coordinate between scanning and your app's work:

  • we start a producer thread putting scans from the Sweep device into a shared queue (non-blocking)
  • we start a consumer thread pulling scans out of the shared queue and doing work on them (blocking)
  • we use a third thread to set off a stop event and cleanly shutdown the pipeline

Windows:

The installed sweep library architecture must match the python version. Ie: if you are using a x86 (32bit) version of python, you must install the x86 (32bit) verison of libsweep.

python.exe setup.py install --user

In the following: replace COM5 with your device's port name (check "Device Manager -> COM Ports").

python.exe -m sweeppy COM5

Quick Start

from sweeppy import Sweep

with Sweep('/dev/ttyUSB0') as sweep:
    sweep.start_scanning()

    for scan in sweep.get_scans():
        print('{}\n'.format(scan))

Note: Sweep objects need to be scoped using the with statement for resource management.

See sweeppy.py for interface and example for example usage.

Interface

class Sweep:
    def __init__(self, port, bitrate = None) -> Sweep

    def start_scanning(self) -> None
    def stop_scanning(self) -> None

    def get_motor_ready(self) -> bool
    def get_motor_speed(self) -> int (Hz)
    def set_motor_speed(self, speed) -> None

    def get_sample_rate(self) -> int (Hz)
    def set_sample_rate(self, speed) -> None

    def get_scans(self) -> Iterable[Scan]

    def reset(self) -> None

class Scan:
    self.samples -> Sample

class Sample:
    self.angle -> int (milli-degree)
    self.distance -> int (cm)
    self.signal_strength -> int ([0:255])

See the libsweep README for a description of how to use a related interface.

Additionally, it is recommended that you read through the sweep Theory of Operation and Best Practices.

Interpret Sample

sample.angle

The sample's angle (azimuth) represents the rotation of the sensor when the range measurment was taken. The value is reported in milli-degrees, or 1/1000 of a degree. For example, a sample.angle value of 180000 milli-degrees equates to 180 degrees (half of a complete rotation). Successive samples of the same scan will have increasing angles in the range 0-360000.

sample.distance

The sample's distance is the range measurement (in cm).

sample.distance

The sample's signal strength is the strength or confidence of the range measurement. The value is reported in the range 0-255, where larger values are better.

License

Copyright © 2016 Daniel J. Hofmann

Distributed under the MIT License (MIT).