fischertechnik TCRT5000 infrared reflective sensor

A compact infrared reflective sensor for fischertechnik, based on the [TCRT5000 reflective optical sensor with transistor output](https://www.vishay.com/docs/83760/tcrt5000.pdf). I needed them for a line-following robot.

Use an analog input pin to measure the signal (sensor out pin). You can use an additional digital output pin to turn the infrared LED on (high) or off (low) (LED on/off pin). Compare two measurements with the LED turned on vs. off to filter out ambient light disturbances. If