===== RPI =====

  * https://www.raspberrypi.org/documentation/hardware/raspberrypi/gpio/README.md
  * https://raspberrypi.stackexchange.com/questions/9298/what-is-the-maximum-current-the-gpio-pins-can-output# 50 mA.
  * https://elinux.org/RPi_Low-level_peripherals#Internal_Pull-Ups_.26_Pull-Downs
  * http://www.raspberrypi.org/documentation/usage/gpio/
  * http://makezine.com/projects/tutorial-raspberry-pi-gpio-pins-and-python/# RpI
  * https://electronics.stackexchange.com/questions/7423/what-is-a-pull-up-and-pull-down#
  * http://razzpisampler.oreilly.com/ch07.html# PullUp are connected to Ground

{{https://i1.wp.com/cdn.makezine.com/uploads/2014/02/rpi-circuit.png?resize=620%2C397}}


==== input ====

  * https://www.raspberrypi.org/forums/viewtopic.php?t=46525#
  * 50kΩ pull up/down resistors 


  * The pins can only source or sink 16mA so limiting the current to that level (with at least 220 ohms) makes sense.
===== MISC ====

  * http://www.sonelec-musique.com/electronique_theorie_led.html
  * http://visualgdb.com/tutorials/raspberry/LED/
  * https://vimeo.com/153263103#connected-tizen-20160131rzr#
  * https://github.com/mozilla-iot/wiki/wiki/Configuring-GPIO-for-use-with-the-gpio-adapter# IoT

===== MORE =====

@TaG: RemoteControl InfraRed [[Io]]