I am proud to present my Arduino super pro mini "serial stereo".
This small project has extraterrestrial abilities :) :) :) :
It has two USB serial ports and through this can provide support for programming and displaying data over the serial plotter and have additionally second port to forward data to the host according to its own specifications (it must emulate a given serial device, the blackbox gateway will not accept dummy ports).
The serial ports are cheap Chinese USB UARTs like that ones:
USB UARTs (https://www.ebay.com/itm/1PCS-6Pin-USB-2-0-to-TTL-UART-Serial-Converter-CP2102-STC-Replace-Ft232/202872145714) they cost around one buck each.
The first serial port is connected regularly as a serial programming cable.
The second serial port is connected to d4d5 as tx-rx and feeds data using softwareSerial.
The interesting part is that the USB UART converters can plug in directly into the USB ports of a Raspberry Pi and on the other side be soldiered on a prototyping board, so you are sure both USB ports will connect together and in the right order.
For my first project I have left the connectors with a 90° angle to have an easy access on all pins, the next copy of it will have directly three layers:
a) the two USB UART converters
b) the prototyping board
c) the Arduino Pro Mini
that would be an extremely compact construction.
The current board has two analog input wired over trim potentiometers and screw terminals providing each
maybe someone would want to make a PCB out of it?