Ultrasonic

In this section, we'll learn how to interface the HC-SR04 ultrasonic sensor with a Raspberry Pi Pico 2. Ultrasonic sensors measure distances by emitting ultrasonic sound waves and calculating the time taken for them to return after bouncing off an object.

We will build a simple project that gradually increases the LED brightness using PWM, when the ultrasonic sensor detects an object distance of less than 30 cm.

🛠 Hardware Requirements

To complete this project, you will need:

• HC-SR04 Ultrasonic Sensor
• Breadboard
• Jumper wires
• External LED (You can also use the onboard LED, but you'll need to modify the code accordingly)

The HC-SR04 Sensor module has a transmitter and receiver. The module has Trigger and Echo pins which can be connected to the GPIO pins of a pico and other microcontrollers. When the receiver detects the returning sound wave, the Echo pin goes high for a duration equal to the time it takes for the wave to return to the sensor.

Setup

Connection for the Pico and Ultrasonic:

• VCC: Connect the VCC pin on the HC-SR04 to the 3.3V pin on the Pico.
  • Although the HC-SR04 generally operates at 5V, using 3.3V helps protect the Pico, as its GPIO pins are rated for 3.3V. There is some unconfirmed information that the Pico 2 GPIO might tolerate 5V, but for now, this is uncertain.
  • I’ve tested both 3.3V and 5V connections without issues so far 🤞. (If anyone has confirmed details on this, please raise an issue so we can keep this guide accurate.)
  • Other considerations: Alternatively, you can use HCSR04+ (which can operate at both 3.3v and 5V) or use logic level shifter.
• Trig: Connect to GPIO 17 on the Pico to start the ultrasonic sound pulses.
• Echo: Connect to GPIO 16 on the Pico; this pin sends a pulse when it detects the reflected signal, and the pulse length shows how long the signal took to return.
• GND: Connect to the ground pin on the Pico.
• LED: Connect the anode (long leg) of the LED to GPIO 3, as in the External LED setup.

Connection for the Pico and LED: