Although old-school machinists typically prefer the mechanical vernier scale on their trusty calipers, many users nowadays buy calipers with a digital readout. These models often come with additional features like differential measurements, or a “hold” function for those situations where you have to maneuver the instrument somewhere deep inside a machine. Another useful feature is a data link that lets you log your measurements on a computer directly instead of manually entering all the values.
The VINCA-branded caliper that [Liba2k] bought has such a data link feature, which requires a USB adapter that’s sold separately. There is a micro-USB connector on the tool itself, but instead of implementing a USB interface, this is used to carry a proprietary serial protocol — a design decision that ought to be classified as a felony if you ask us. Rather than buying the official USB adapter, [Liba2k] decoded the protocol and built his own interface called VINCA Reader that can connect through either USB or Wi-Fi.
The serial format turned out to be a simple serial bus that clocks out 24 bits at a time. In order to adapt its 1.2 V signal level to the 3.3 V used by an ESP32, [Liba2k] designed a simple level shifter circuit using a handful of discrete components. The ESP can communicate with the computer through its Wi-Fi interface, for which [Liba2k] wrote a spreadsheet-like application; alternatively, an ordinary USB cable can be connected to emulate a keyboard for use with any other software.
With its added Wi-Fi feature, the VINCA Reader is actually more complete than the official USB adapter, and will probably be cheaper as well. The serial interface appears to be common to all caliper manufacturers, although many went for a more sensible connector than micro-USB. An automated readout system is particularly handy if you have to make thousands of similar measurements.