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Interfacing Launchpad to Digital Caliper

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Hello there,

I'm new here and this is my first Launchpad project. May I apply for project of the moth contest? ;) (BTW this is cool idea as those kind of things always help to find motivation to describe what you did not just stop when you see everything is working)


I recently bought digital caliper and decided to try to read it's data port readings from my Launchpad. One of uses would be to use caliper for precise position sensor if 8Hz updates are enough. It had Clock and Data pin. Had to setup pin that connects to Clock to trigger interrup on every pulse and then in interrupt function do bit shifting to assemble 16 bit signed integer representing caliper reading. Then sent it out to PC via soft UART serial port. For that I reused examples from well known blog at http://www.msp430launchpad.com/.


Also I had to figure out how to connect calipers lines to MSP430 as caliper is using 1.5V levels where MSP430 +3V levels. Used two transistors and two resistors and breadboard to amplify levels. Schematics:



Also took caliper apart just to find out what principle is used to sense position changes:



You can find full source code and detailed explanation in article I worte:



Let me know if you have any questions or suggestions!

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Welcome Maris! Glad you posted here! Judging by your project, I think you'll fit right in with the others in this forum. :D


Since you're a forum member now (have to be a member for a week to enter), I think you'll qualify for the contest as long as you make a few more (hopefully meaningful ;) ) posts. See the rules here.

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If you mean just use current schematics and NPN transistor and connect transistor pin that is now connected to ground (emitter), connect it to VCC, then it won't work. Voltage difference on base (pin on right) needs to be higher than on emitter for transistor to open. So, if we connect VCC +3V to emitter then there is no way it will open as maximum that can be applied to base is +1.5V from caliper. Using PNP transistor it's OK to apply VCC to emitter, but then again, transistor opens if there is low signal at base, so we apply VCC when there is 0at base, so inversion again.


Now I'm thinking - maybe with FETs (MOSFETS) it might be possible to connect so that it's not inverted, but I'm not that sure. I have to admit I'm not the strongest in analog electronics part.

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thanks everyone, good to be there. and the comments there are usually rough and fun to read. u can get all kind of criticism, not on this one though and there is always comparison between AVRs and PICs. i guess a MSP430 project won't get people stand on opposite side.



lol, wrong thread, i thought this is about my project. we are making HaD too frequent.


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