Using Ultrasonic sensor to measure distance

Ameba RTL8722DM is a low-power dual-band WLAN and Bluetooth Low Energy SoC by Realtek. The RTL8722DM also include memory for Wi-Fi protocol functions and application making it simple for anyone to develop various kind of IoT applications. At the same time it has a wide range of peripheral interfaces. With all these interfaces, it can connect to most of the electronics components like LEDs, temperature and humidity sensors, and so on.

The way the Ultrasonic module works is that first we “toggle high” the TRIG pin (that is to pull high then pull low). The HC-SR04 would send eight 40kHz sound wave signal and pull high the ECHO pin. When the sound wave returns back, it pull low the ECHO pin.

Assume the velocity of sound is 340 m/s, the time it takes for the sound to advance 1 cm in the air is 340*100*10^-6 = 29 us。 The sound wave actually travels twice the distance between HC-SR04 and the object, therefore the distance can be calculated by (time/29) / 2 = time / 58。

More Resources:

If you need additional technical documents or the source code for this project. Please visit the official websites and join the Facebook group and forum.

• Ameba Official Website: https://www.amebaiot.com/en/
• Ameba Facebook Group: https://www.facebook.com/groups/amebaioten
• Ameba Forum: https://forum.amebaiot.com/