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 air at 343.2 meters per second

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).

• Author(s): Mike Mabey

class hcsr04.HCSR04(trig_pin, echo_pin)

Control a HC-SR04 ultrasonic range sensor.

Example use:

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

Parameters:

• trig_pin (str or microcontroller.Pin) – The pin on the microcontroller that’s connected to the Trig pin on the HC-SR04.
• echo_pin (str or microcontroller.Pin) – The pin on the microcontroller that’s connected to the Echo pin on the HC-SR04.

deinit()

De-initialize the trigger and echo pins.

dist_cm()

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, the return value will be -1. 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

hcsr04.test(trig, echo, delay=2)

Create and get distances from an HCSR04 object.

This is meant to be helpful when first setting up the HC-SR04. It will get a distance every delay seconds and print it to standard out.

Parameters:

• trig (str or microcontroller.Pin) – The pin on the microcontroller that’s connected to the Trig pin on the HC-SR04.
• echo (str or microcontroller.Pin) – The pin on the microcontroller that’s connected to the Echo pin on the HC-SR04.
• delay (int or float) – Seconds to wait between triggers.

Return type:

None