This is an electronic digital caliper to computer (RS-232) interface. This will work with the inexpensive calipers, micrometers and height gauges that are typically made in China. The connector on the measuring instrument will have 4 pins, and the owner's manual will typically describe the output as 24 bit 90 kHz synchronous. This does not work the name brand instruments - Fowler, Mitutoyo, Brown & Sharpe, etc..
The code contains examples of: * 9600 bps asynchronous receiver/transmitter * 90 kHz synchronous receiver * host command processing * tables for data and text * sending text to host * 24 x N bit fractional multiplication * 24 bit addition * binary to BCD conversion * BCD to ASCII conversion * ASCII transmission with leading zero suppression and fixed decimal place * operational mode set by jumpers or override by host * Use of watchdog timer The circuit contains examples of: * +5V/-1.5V power from serial port * 1.5V to 5V logic level conversion * minimal PIC to RS-232 interface
P.S. An updated version is available at:
http://www.pcmx.net/gauge
This board is available from Olimex