 0-15 all have a built-in pull-up resistor, just like in an Arduino. GPIO16 has a built-in pull-down resistor.</p>
   <h4>PWM</h4>
   <p>Unlike most Atmel chips (Arduino), the ESP8266 doesn’t support hardware PWM, however, software PWM is supported on all digital pins. The default PWM range is 10-bits @ 1kHz, but this can be changed (up to &gt;14-bit@1kHz).</p>
   <h3>Analog input</h3>
   <p>The ESP8266 has a single analog input, with an input range of 0 - 1.0V. If you supply 3.3V, for example, you will d