Introduction¶
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.
Installing from PyPI¶
On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally from PyPI. To install for current user:
pip3 install adafruit-circuitpython-hcsr04
To install system-wide (this may be required in some cases):
sudo pip3 install adafruit-circuitpython-hcsr04
To install in a virtual environment in your current project:
mkdir project-name && cd project-name
python3 -m venv .env
source .env/bin/activate
pip3 install adafruit-circuitpython-hcsr04
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.
Documentation¶
For information on building library documentation, please check out this guide.
Table of Contents¶
Simple test¶
Ensure your device works with this simple test.
1 2 3 4 5 6 7 8 9 10 11 12 | import time
import board
import adafruit_hcsr04
sonar = adafruit_hcsr04.HCSR04(trigger_pin=board.D5, echo_pin=board.D6)
while True:
try:
print((sonar.distance,))
except RuntimeError:
print("Retrying!")
time.sleep(0.1)
|
adafruit_hcsr04
¶
A CircuitPython library for the HC-SR04 ultrasonic range sensor.
The HC-SR04 functions by sending an ultrasonic signal, which is reflected by many materials, and then sensing when the signal returns to the sensor. Knowing that sound travels through dry air at 343.2 meters per second (at 20 °C), it’s pretty straightforward to calculate how far away the object is by timing how long the signal took to go round-trip and do some simple arithmetic, which is handled for you by this library.
Warning
The HC-SR04 uses 5V logic, so you will have to use a level shifter or simple voltage divider between it and your CircuitPython board (which uses 3.3V logic)
- Authors:
- Mike Mabey
- Jerry Needell - modified to add timeout while waiting for echo (2/26/2018)
- ladyada - compatible with
distance
property standard, renaming, Pi compat
-
class
adafruit_hcsr04.
HCSR04
(trigger_pin, echo_pin, *, timeout=0.1)[source]¶ Control a HC-SR04 ultrasonic range sensor.
Example use:
import time import board import adafruit_hcsr04 sonar = adafruit_hcsr04.HCSR04(trigger_pin=board.D2, echo_pin=board.D3) while True: try: print((sonar.distance,)) except RuntimeError: print("Retrying!") pass time.sleep(0.1)
Parameters: - trigger_pin – The pin on the microcontroller that’s connected to the
Trig
pin on the HC-SR04. - echo_pin (microcontroller.Pin) – The pin on the microcontroller that’s connected to the
Echo
pin on the HC-SR04. - timeout (float) – Max seconds to wait for a response from the sensor before assuming it isn’t going to answer. Should not be set to less than 0.05 seconds!
-
distance
¶ Return the distance measured by the sensor in cm.
This is the function that will be called most often in user code. The distance is calculated by timing a pulse from the sensor, indicating how long between when the sensor sent out an ultrasonic signal and when it bounced back and was received again.
If no signal is received, we’ll throw a RuntimeError exception. This means either the sensor was moving too fast to be pointing in the right direction to pick up the ultrasonic signal when it bounced back (less likely), or the object off of which the signal bounced is too far away for the sensor to handle. In my experience, the sensor can detect objects over 460 cm away.
Returns: Distance in centimeters. Return type: float
- trigger_pin – The pin on the microcontroller that’s connected to the