Reading Digital caliper with Arduino

[arvidj]

On the Uno there are 4 interrupt modes available on pin 2 or 3 ... low, changing, rising and falling. I think falling is the one we would be looking for so we can read the value from the data line.

Then a variable to keep track of the last time the interrupt occurred to determine if it is the start of a string of digits [which implies the previous string of digits are complete], the start of a new bcd digit in the new string [which implies the previous bcd digit is complete] or the start of a new bit in the current bcd digit [which implies the previous bcd bit is complete].

Or a variable to keep track of the last time the interrupt occurred to allow syncing up on the start of a string of digits and then simple dead reckoning for the proper placement of the data line value in the string for the next 23 transitions.

Or ...

Anyway, the code is pretty straight forward and if our GoogleFoo is any good we can probably find something someone else has already written  .