I need to connect a GNSS module's RXD and TXD lines to my MCU. But the problem is I don't have any available UART connections on my MCU. There are 3 UART connections, one is used by flash, one is used for firmware uploads, and the last is connected to a LTE module.
Because I seldom update the firmware, this UART connection is somewhat wasted and I'd like to use it to connect to a GNSS module. Is there a way that I could use an array of transistors to only connect the RXD/TXD lines to firmware upload circuit when it is needed? Like when Vdd is detected at the micro-usb port of the MCU. The rest of the time the UART lines would be connected to the GNSS module.
Note that unless we are performing a firmware update, a battery is being used so any excessive power consumption is detrimental to the overall design. Below is the circuit used to upload firmware to the ESP through micro-USB which is then bridged to UART connection.