I've searched the internet high and low, and while I suspect the answer to my problem will be obvious in retrospect, I can't find anything to help me understand what I need to do differently. In an effort to simplify the problem as much as possible, I've programmed the MSP430 with a simple program that lights up the LED on P1.0. I'm using CCS v.5 with the good ol Launchpad. Everything works as expected on the launchpad, including my more complicated programs.
But when I place the chip onto a solderless breadboard for testing "outside the womb" it does nothing. I have tried supplying the chip with 3v from AA's and also whatever voltage is coming off the header pins of the launchpad. The led lights up if I connect the led directly to the VCC and GND of the power supply going into pins 1 & 20, but when I plug it into Pin 2, or any pin for that matter, it does nothing.
I'm new to all this, so I assume I'm missing something obvious...Is the launchpad not actually programing the chip? Is this something to do with debug mode versus release mode? Do I need any capacitors or resistors to make the chip work on its own? I've tried a couple chips now (g2353's) with no luck. This has really put a damper on the whole project, it would be very appreciated if someone could grace me with a tip and possibly a "doh!" moment.
Have you biased the RST pin on your breadboard? The launchpad does indeed program the chip so if it runs in the launchpad your program is on it :)
Looking at the Family User Guide Section 2.5 Connection of Unused Pins / Page 44 they recommend the following setup: 47 kΩ pullup with 10 nF (2.2 nF (1)) pulldown
(1) The pulldown capacitor should not exceed 2.2 nF when using devices with Spy-Bi-Wire interface in Spy-Bi-Wire mode or in 4-wire JTAG mode with TI tools like FET interfaces or GANG programmers.
MSP430 Launchpad GitHub: https://github.com/alanbarr/msp430-launchpad
Hmm..no I haven't, I'll have to try that next. Now my next question: Why would I do a pulll up and a pull down on the same pin? I bought the 47k resistor and a 10nF capacitor but I'm not sure how to wire them up....On that note, do you understand why they are necessary? I will keep researching as well and post back with my results. Thanks!
well, duh I just checked the pdf for the launchpad and it has a schematic that shows the capacitor and resistor connected to the rst pin, so I'll start by mimicking their setup, That still doesn't explain what the purpose of doing this is. If you have any insight, please share!
The capacitor is not absolutely necessary. But the resister is.
Take a look at the LaunghPad board. The PCB has pads to solder both the resistor and the capacitor, TI sometimes do not load the capacitor. Unlike some other micros, MSP430 does not depend on the RC time to generate the reset signal. The capacity is used mostly to reduce noise pickup.
old_cow_yellowMSP430 does not depend on the RC time to generate the reset signal.
So sometimes an additional RC delay on RST is required. Or a 'power good' signal from the regulator.
If you're unsure whether your supply will always deliver full VCC quick enough, add the RC. It won't hurt, and better safe than sorry.
_____________________________________Before posting bug reports or ask for help, do at least quick scan over this article. It applies to any kind of problem reporting. On any forum. And/or look here.If you cannot discuss your problem in the public, feel free to start a private conversation: click on my name and then 'start conversation'. But please do so only if you really cannot do it in a public thread, as I usually read all threads. And I prefer to answer where others can profit from it (or contribute to it) too.
I forgot to do a final reply. This was definitely the fix, so thanks to all! My circuit works exactly as expected.
I'm about to move my first MSP430 program off the launchpad and into my circuit board, and have been wondering what I needed to watch out for -- so this discussion has been very helpful! Thanks to all from me as well..
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