Which Digital Caliper can be interfaced with microcontroller?

[eeguy]

Hello, quite a few people on the internet used what they called "cheap" "Chinese" digital calipers to interface with microcontroller. They showed that there are four ports (power, gnd, clock, data) inside the top right of the LCD screen. I cannot find such product and several sellers told me that theirs have no such capability. Know any which would work?

[rcjoy]

Look for calipers with "SPC output".

[jpanhalt]

There are several that that SPC or SPD output: https://www.greatgages.com/collections/digital-calipers-with-spc-output

The Mitutoyo -- at least some of them -- is a little different than the "cheap" versions.  I have code for the Mitutoyo.  I also have a very old link to the cheap versions, if that is what you decide to get.  I would post the latter now, but it will take some digging to find.

Edit: Found it:
 https://www.compendiumarcana.com/caliper/

[eeguy]

How many different kinds of protocols are used in these digital calipers?

It seems that except for very expensive ones that have data cable sold separately and with the issue that data point are collected not continuously but only when a button is pressed, do those cheap ones actually all have four pins on the circuit board but they are only accessible when the user open the case?

[jpanhalt]

How many different kinds of protocols are used in these digital calipers?

Why do you care how many?  The more important question is the register map and how to address it.  As for reading Mitutoyo, that information is readily available. 

I have used Mitutoyo since the time it was the best of the cheap imports.  Now, it is held in higher esteem.  BUT, Mitutoyo is noted in my mind for telling you how to use its expensive (today) black boxes, but not what goes on inside. 

As for the data cables, the cable plugs to Mitutoyo's dial indicators and calipers is a special plug.  It's other connectors are quite standard.  And yes, the cable connector to its dial indicator is outrageously expensive for what it is.  I keep mine in a safe-deposit box at the bank.

[spostma]

also search for terms like "digital vernier interfacing"...

Some useful links on this subject:
https://www.instructables.com/Reading-Digital-Callipers-with-an-Arduino-USB/
https://www.robotroom.com/Caliper-Digital-Data-Port.html
https://hackaday.com/2016/05/17/improved-digital-caliper-interfacing-including-3d-printed-connector/
https://www.instructables.com/Interfacing-a-Digital-Micrometer-to-a-Microcontrol/
https://hackaday.com/2020/08/02/digital-caliper-talks-for-accessibility-with-this-app/
https://www.compendiumarcana.com/caliper/

digital scales use the same digital interface as digital calipers, so this link is also useful.
https://www.yuriystoys.com/p/android-dro.html

By the way, I just bought this digital caliper that is accurate to 0.02mm, has a big display and CR2032 battery, and seems to be of good quality:
https://www.aliexpress.com/item/1005005210593806.html

[jpanhalt]

I just bought a used Mitutoyo 543-003 "presetter" for $0.05 on the dollar compared to new.  If it works, I will post the results.  I will probably need help deciphering the code

Regards, John

[linux-works]

I'm working on this very subject (for fun) right now.

I bought some igaging micrometers and dial gauges and the current models with micro-usb connectors on them work.  I have working esp8266 code that works great with them.  (will be posting to my github soon).

not every micro-usb connector speaks this.  and its NOT usb!  dont even think to plug into a pc.