HC-SR04 Reader Module to Relieve Arduino
π Overview
The HC-SR04 ultrasonic module does not handle its own timing - the host microcontroller has to babysit every pulse measurement, which eats a lot of time. This project builds a standalone reader module: a small microcontroller triggers the pulses and works out the distance itself, while the Arduino just reads the result over I2C or serial.
Ideal for projects with many sensors - outsource the fiddly ranging work and let the host focus on the important logic.
π§° What you need
- HC-SR04 ultrasonic module x1
- Small microcontroller (ATtiny85 or similar; the author has a matching solution)
- Potentiometer (fine adjustment)
- Header pins (male/female) + jumper wires
- USBasp programmer (to flash the microcontroller)
π§ Step by step
Gather the parts
The core idea: use a dedicated MCU instead of the Arduino to handle HC-SR04 timing
The author also sells the finished board on Tindie if you would rather buy one
PCB, schematic, and files
The author provides the schematic and fabrication files
You can make your own board or build it on perfboard - the circuit is simple
Solder it
Use tweezers and a fine tip for the small packages and watch for solder bridges
Match the header pin direction to how the board will be mounted
Flash the firmware
Flash the ranging firmware with a USBasp
The pulse timing and output format are hard-coded in the firmware
Test and fine-tune
Read the data with an Arduino and compare it against a measured distance
Tweak the threshold and filter parameters with the potentiometer for a steadier reading
Extend it
It gives stable centimetre-level readings, good for obstacle avoidance, tank levels, and parking aids
With several sensors the host only has to read results, which takes a lot of pressure off it
π‘ Tips
- The HC-SR04 output is 5V logic - use level shifting when connecting it to a 3.3V host
- Distance readings depend on air temperature; high-accuracy work should compensate for it
- Give the module a 3D-printed bracket; fixing the mounting angle makes readings steadier