Everyone nowadays is familiar with screens with which you can draw or type by touching a finger or a pen to the screen. How do such screens work, and how is the point of contact read out?The circuit presented in this article makes it very easy to use a touch screen in your own projects. All that you need is a single IC, which is a standard microcontroller costing only a few pounds. The circuit is self-calibrating and very energy efficient.There are several different types of touch screens. Some are based on capacitance or resistance, while others use optical effects or guided waves. The circuit described here is limited to resistive touch screens, since these are inexpensive and can easily be read out.