❓ Problem

It's tedious to write down digital caliper measurements while working with research samples since you have to set the calipers down each time to record the value.

✔ Solution

Use SAM32 to read the caliper measurement, decode the protocol, and emulate keystrokes over USB to enter data into spreadsheet. Note: wired design driven by @CaitlynBioE's specific use-case.

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/31f62927-af70-40ec-b750-e45f956bb111/demo3.gif

Jump to the SAM32 code


Choosing the Right Calipers

Enabling USB input from digital calipers is expensive: Amazon Mitutoyo USB Input Cable runs $174 on top of the already $150 calipers! But, it shows us there's at least an interface to work with (on some models). You can see by the product image that the cable mates with a 4-pin press-fit connector on the body of the calipers.

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/25b6f4a0-76ec-4ea4-b0e3-4694edf3fe50/Untitled.png

Not all calipers will have output capability. In fact, after tearing down the most popular budget calipers on Amazon: [iGaging IP54 Electronic Digital Caliper](iGaging IP54 Electronic Digital Caliper) we see that the glob-topped IC driving the linear encoder doesn't even have the data-output pins available for us to use.

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/d3dfa30c-faf7-47d2-90c4-4365ac6358ca/Untitled.png

Logic board in the [iGaging IP54 Digital Caliper](iGaging IP54 Electronic Digital Caliper) circa 2018. Notice data output pins are not made available

Logic board in the [iGaging IP54 Digital Caliper](iGaging IP54 Electronic Digital Caliper) circa 2018. Notice data output pins are not made available

The easiest way to tell if you have a pair of calipers with output capability is to look for the model of encoders packaged in caliper bodies with a port (or door) in the top right corner of the device as shown to the right.

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/844a5822-b111-4f5a-8a47-df1c8bf49fff/Untitled.png

Understanding the Data

Folks have already documented the types of data presented by digital caliper ports. I found the following pages very helpful:

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