Maris 3 Posted December 13, 2010 Share Posted December 13, 2010 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: http://robocombo.blogspot.com/2010/12/using-tis-launchpad-to-interface.html Let me know if you have any questions or suggestions! tingo, bluehash and NJC 3 Quote Link to post Share on other sites
GeekDoc 226 Posted December 13, 2010 Share Posted December 13, 2010 Welcome Maris! Glad you posted here! Judging by your project, I think you'll fit right in with the others in this forum. 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. Quote Link to post Share on other sites
bluehash 1,581 Posted December 13, 2010 Share Posted December 13, 2010 Front page . Thanks for sharing Maris. Edit: Raced by Doc again. Quote Link to post Share on other sites
GeekDoc 226 Posted December 13, 2010 Share Posted December 13, 2010 Edit: Raced by Doc again. LOL First! Quote Link to post Share on other sites
Maris 3 Posted December 13, 2010 Author Share Posted December 13, 2010 Wow, what a warm welcome! Nice feature on the front page, now I'm for sure I do feel obligated to make some more meaningful posts. I'll stick around, you have nice community here. Quote Link to post Share on other sites
cde 334 Posted December 13, 2010 Share Posted December 13, 2010 Why not wire the transistors to VCC, and have the msp430 pins use the pull down resistors? Then no need for software inverting. Quote Link to post Share on other sites
Maris 3 Posted December 14, 2010 Author Share Posted December 14, 2010 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. Quote Link to post Share on other sites
GeekDoc 226 Posted December 14, 2010 Share Posted December 14, 2010 Actually, I think he means collector to Vcc (3v) and emitter to pin (with pull-down resistor). This is what I thought to start out, but I'm not the EE guru here! :? Quote Link to post Share on other sites
Maris 3 Posted December 14, 2010 Author Share Posted December 14, 2010 I think this was what tried first too, but it didn't work. I think It must have to do something with fact that in this way, emitter is connected to ground through Launchpads pull-down resistor. So, maybe base-emitter had not enough voltage. Quote Link to post Share on other sites
NatureTM 100 Posted December 14, 2010 Share Posted December 14, 2010 Hi. Thanks for sharing the source and the information. Someone could easily reproduce your project with your documentation. That's a nice first launchpad project. I bet it would make a good linear encoder for some robotics. Good luck with the contest! Quote Link to post Share on other sites
simpleavr 399 Posted December 15, 2010 Share Posted December 15, 2010 another project made HaD congrats. http://hackaday.com/2010/12/15/reading- ... ontroller/ bluehash and Maris 2 Quote Link to post Share on other sites
Maris 3 Posted December 15, 2010 Author Share Posted December 15, 2010 he, cool, thanks for link. looks like hackaday is quite popular, I see from trafic Quote Link to post Share on other sites
gatesphere 45 Posted December 16, 2010 Share Posted December 16, 2010 Congrats on making HaD! I wish I was cool and innovative like all of them are Quote Link to post Share on other sites
simpleavr 399 Posted December 16, 2010 Share Posted December 16, 2010 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. [EDIT] lol, wrong thread, i thought this is about my project. we are making HaD too frequent. [/EDIT] Quote Link to post Share on other sites
bluehash 1,581 Posted December 16, 2010 Share Posted December 16, 2010 Congrats Maris. Quote Link to post Share on other sites
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