In some situations, it can be useful to simulate user events on a keyboard or mouse, without an actual keyboard or mouse. The original idea that made me look into this subject, was that I wanted to run RetroPie on my Raspberry Pi with different ways to control the system. Instead of a keyboard, I wanted to use GPIO inputs (buttons or joysticks), or even a web interface that I could access from my phone. We’ll use a program called xdotool to do this.
We learned in the first part of this tutorial how to measure a distance with a HC-SR04 ultrasonic sensor. In this second part, we’ll get rid of the LCD display, and instead show the distance on a custom meter made with LEDs. The idea is to turn colored LEDs ON/OFF depending on how close the car is from the wall.
If you don’t have a reverse backup radar system in your car, or if you park forward in your garage, you probably know this feeling of “am I too close, am I gonna hit the wall??”. Well, in this 2 part tutorial, we’re going to create a simple system to detect how close to the wall your car is.