Hi, the only reason I wanted an additional UART for programming was to support USB port programming. The benefits of programming over USB are primarily doing away with the need for an external ISP programming module, and perhaps protecting a custom bootloader from inadvertent tampering. But this is just a suggestion. Like an Arduino, we could have both USB programming and and expose the ICSP header.
Anyway if we dedicated one UART port to the ESP8266 module for data transmission, it means we only have one port for sensor input. Because it’s likely that external sensors connected to module only transmit sporadically, it would be a pity to physically bind a single sensor to the one remaining UART port permanently.
So, to have at least two sensors available I thought we could multiplex the second UART. And it follows that we could easily do the same for UART 0 because the code would still have to written for UART , and as a bonus gain the ability to add yet another sensor.
It really just depends on how many serial sensors we might expect to connect at one time. If desired, I can happily remove the USB port and one or both MUX chips.