leo.martinez_oto 0 Posted May 22, 2012 Share Posted May 22, 2012 Hi, I have a little problem with my msp430. I am sourcing it through a lm317 which transforms the 3.3v of a battery to 1.8 v. Then i am trying to light some leds. The problem is that it doesn Quote Link to post Share on other sites
Rickta59 589 Posted May 22, 2012 Share Posted May 22, 2012 What voltage does your led use? Maybe 1.8 v isn't enough to turn it on. Quote Link to post Share on other sites
leo.martinez_oto 0 Posted May 22, 2012 Author Share Posted May 22, 2012 What voltage does your led use? Maybe 1.8 v isn't enough to turn it on. Yes, it is 1.8 V. It's checked. The problem is that nothing happens. Whereas, doing the same to the launchpad it works ok. Now, i am connecting a dc transformer from main power to the lm317 but i have a 50 hz wave in each led. Just in that pins of the msp430... It's really strange... I think that i am forgetting something that the launchpad has. Quote Link to post Share on other sites
rockets4kids 204 Posted May 22, 2012 Share Posted May 22, 2012 The LM317 has a pretty high drop-out. Try it with a 5-6 V source. Quote Link to post Share on other sites
leo.martinez_oto 0 Posted May 22, 2012 Author Share Posted May 22, 2012 The LM317 has a pretty high drop-out. Try it with a 5-6 V source. I have checked it with mu oscilloscope and it works ok. It is not about the input of lm317 because the output it's fine... Quote Link to post Share on other sites
Rickta59 589 Posted May 22, 2012 Share Posted May 22, 2012 What speed are you using for the MCU? Are you using the DCO? looks like you need to be < 5 MHz @ 1.8 volts. Quote Link to post Share on other sites
SugarAddict 227 Posted May 22, 2012 Share Posted May 22, 2012 Is there a 47k pullup on the reset pin of the MSP430? Quote Link to post Share on other sites
hlipka 11 Posted May 22, 2012 Share Posted May 22, 2012 According to the data sheet, the output ports have a voltage drop of 0.3 volts. So they can deliver only 1.5 volts in your case, which might be too low. Can you check with a multimeter that the ports are active at all? Have you checked that the output of the LM317 really is 1.8 volts? And what do you mean with "50 hz wave in each LED"? Quote Link to post Share on other sites
Rickta59 589 Posted May 22, 2012 Share Posted May 22, 2012 Is there a 47k pullup on the reset pin of the MSP430? I just saw his schematic posted on the e2e.ti.com forum. He doesn't have a pull up on his configuration .. jeez I thought he had a working system. He doesn't. You need a pull-up and probably a small cap. I guess the first question should be post a schematic or a picture. When you fix this and add the pull up, power the board first with the launchpad 3.3 v and its regulator to make sure that works. If that does work then try your lm317 setup. -rick Quote Link to post Share on other sites
Rickta59 589 Posted May 22, 2012 Share Posted May 22, 2012 This post has useful information on how to set up a barebones msp430 that works. http://www.43oh.com/forum/viewtopic.php?f=8&t=1152&p=7679#p7679 -rick Quote Link to post Share on other sites
leo.martinez_oto 0 Posted May 23, 2012 Author Share Posted May 23, 2012 Hi all, Thanks for that. I was forgetting the rst pin. How silly... Thanks. Quote Link to post Share on other sites
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