JohnsUPS
Posts: 188
Joined: Fri Jul 06, 2018 2:13 am
Location: USA

Re: Please help me understand the clock pin of Serial RS232 communication

Wed Feb 26, 2020 11:16 am

I did exactly this a while back using cheap Chinese calipers. During my research into the protocol, I came across the Mitutoyo information, and also having a Mitutoyo caliper, I was interested in decoding it too. However their serial protocol is much different, so I opted to skip.

Because you already have this "input tool", I would focus on using it. Let the tool take care of the manufacturer-specific protocol between the caliper and the tool, and just focus on the RS232 interface side. This will probably save a lot of coding time. I'm sure there is a micro inside the tool running code that does the translation - no need to reinvent the wheel.

As for interfacing the "input tool" to the Pi, you'll need to convert the RS232 interface voltages down to something that the Pi can handle.

drgeoff
Posts: 11240
Joined: Wed Jan 25, 2012 6:39 pm

Re: Please help me understand the clock pin of Serial RS232 communication

Wed Feb 26, 2020 11:48 am

Use a USB to "real RS-232" module to connect RPi to the tool. A USB to "TTL-serial", even one that has 3.3 volt levels on the TTL side will not work.

The "real RS-232" module will have a 9 pin D-type connector.
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keystone76
Posts: 11
Joined: Wed Jan 10, 2018 1:19 am

Re: Please help me understand the clock pin of Serial RS232 communication

Wed Feb 26, 2020 6:29 pm

Hippy,

Thank you very much! I think this is what I was looking for. When I get a chance to try it I will give everyone an update.

I do think the gage is 5V logic. Does anyone know how to test it and see? Either way, I've got some bi-directional logic level converters on the way.

Thanks again!!!

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