ESP8266 Serial
Serial.swap(); // Hardware serial is now on RX:GPIO13 TX:GPIO15 // use SoftwareSerial on regular RX(3)/TX(1) for logging logger = new SoftwareSerial(3, 1);
UART0
U0_TXD = IO1 U0_RXD = IO3 can be remapped to GPIO15 (TX) and GPIO13 (RX)
UART1
U1_TXD = IO2