In it, he shows an example of using all three ESP32 UARTs from an Arduino program. He calls the third port “secret” although that’s really a misnomer.

Connecting the Intel® Edison board to your Android* Phone with Serial Port Profile (SPP) describes how to connect your Edison board to Android* Phone with SPP, however, you cannot get the input ...

Eight digital outputs act as the parallel interface. When a byte is received over serial, the individual bits are set on the individual digital lines connected to the printer’s parallel port.