USB to TTL CH340

This USB to Serial device will work with logic level 5.0V and 3.3V devices. (jumper selectable) and exposes RX and TX lines.  It will work with Arduino Pro Mini and ESP8266 devices, but you will need to toggle the reset line manually.  If you are so inclined, it is relatively easy to solder wires directly onto the chip leads and expose all of the flow control lines like RTS, CTS, DSR, DTR.