Introduction

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The HC-SR04 is an inexpensive solution for measuring distances using microcontrollers. This library provides a simple driver for controlling these sensors from CircuitPython.

Dependencies

This driver depends on:

Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle.

Usage Example

Warning

The HC-SR04 uses 5V logic, so you will have to use a level shifter between it and your CircuitPython board (which uses 3.3V logic).

Note

If you want to use an HC-SR04 with MicroPython, I recommend checking out this library.

You’ll need to dedicate two pins to communicating with the HC-SR04. The sensor communicates in a very rudimentary manner, so it doesn’t matter which pins you choose, as long as they’re digital IO pins (pins that start with “D” are digital).

There are two ways of instantiating a HCSR04 object: with or without using a context manager.

Note

It is technically possible to communicate with the HC-SR04 using only one wire since the trigger and echo signals aren’t ever active at the same time. Once I have a chance to determine a safe way to do this, I plan to add this as a feature to the library.

See also

Adafruit’s guide on Lifetime and ContextManagers
Gives more info on using context managers with CircuitPython drivers.
board

A list of pins available on your device. To view this list, first get a REPL (the guide linked was written for the pyboard, but it still works), then input the following:

import board
dir(board)

Without a Context Manager

In the example below, we create the HCSR04 object directly, get the distance every 2 seconds, then de-initialize the device.

from adafruit_hcsr04 import HCSR04
sonar = HCSR04(trig, echo)
try:
    while True:
        print(sonar.dist_cm())
        sleep(2)
except KeyboardInterrupt:
    pass
sonar.deinit()

With a Context Manager

In the example below, we use a context manager (the with statement) to create the HCSR04 instance, again get the distance every 2 seconds, but then the context manager handles de-initializing the device for us.

from adafruit_hcsr04 import HCSR04
with HCSR04(trig, echo) as sonar:
    try:
        while True:
            print(sonar.dist_cm())
            sleep(2)
    except KeyboardInterrupt:
        pass

Contributing

Contributions are welcome! Please read our Code of Conduct before contributing to help this project stay welcoming.

Building locally

Zip release files

To build this library locally you’ll need to install the circuitpython-build-tools package.

python3 -m venv .env
source .env/bin/activate
pip install circuitpython-build-tools

Once installed, make sure you are in the virtual environment:

source .env/bin/activate

Then run the build:

circuitpython-build-bundles --filename_prefix adafruit-circuitpython-hcsr04 --library_location .

Sphinx documentation

Sphinx is used to build the documentation based on rST files and comments in the code. First, install dependencies (feel free to reuse the virtual environment from above):

python3 -m venv .env
source .env/bin/activate
pip install Sphinx sphinx-rtd-theme

Now, once you have the virtual environment activated:

cd docs
sphinx-build -E -W -b html . _build/html

This will output the documentation to docs/_build/html. Open the index.html in your browser to view them. It will also (due to -W) error out on any warning like Travis will. This is a good way to locally verify it will pass.

Indices and tables