During the past 16 years I have been playing a lot with a variety of embedded devices.
One of the most important tasks for debugging or analyzing embedded devices is usually
to get access to the serial console on the UART of the device. That UART is often exposed
at whatever logic level the main CPU/SOC/uC is running on. For 5V and 3.3V that is easy,
but for ever more and more unusual voltages I always had to build a custom cable or a custom
In 2016, I finally couldn't resist any longer and built a multi-voltage USB UART adapter.
This board exposes two UARTs at a user-selectable voltage of 1.8, 2.3, 2.5, 2.8, 3.0 or 3.3V.
It can also use whatever other logic voltage between 1.8 and 3.3V, if it can source a reference
of that voltage from the target embedded board.
Rather than just building one for myself, I released the design as open hardware under CC-BY-SA
license terms. Full schematics + PCB layout design files are available.
For more information see mv-uart.
In case you don't want to build it from scratch, ready-made machine assembled boards are also made
available from sysmocom