s means that UART1 can only transmit data.</p>
   <p>UART0 also has hardware flow control on pins 15 and 13 (RTS0 and CTS0 resp.). These two pins can also be used as alternative TX0 and RX0 pins.</p>
   <h4>I²C</h4>
   <p>The ESP doesn’t have a hardware TWI (Two Wire Interface), but it is implemented in software. This means that you can use pretty much any two digital pins. By default, the I²C library uses pin 4 as SDA and pin 5 as SCL. (The data sheet specifies GPIO2 as SDA and GPIO14 as SCL.) The maxi