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rockets4kids

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Everything posted by rockets4kids

  1. Do you have a video of the device in action? How does speed compare with typing? Are you only doing fingerspelling, or are you recognizing word-signs as well?
  2. It has been a long time since I actually went to conferences, but I have noticed that in the videos I have watched of the presentations, almost all of the best presenters are using OS X. What is particularly difficult to understand is why TI would choose to support Linux and not OS X, since getting something running on Linux is 99% of the way towards getting something to run on OS X.
  3. Well, seeing as this is developmental software which is still a long way from even an alpha level release, I am willing to withhold judgement. However, I do think that it is rather irresponsible of TI to release software in this state without any notification that it is still developmental software.
  4. Which part of Java are you talking about? The VM? The compiler? The applications written in it? The VM or language specifications?
  5. What does your meter read against a reference source? More than likely you have some resistance in your cables and connectors.
  6. When the voltage is too low for a given clock speed the cpu simply won't run. There is a small window where you'll get erratic behavior, lockups, etc. Executing faster and sleeping more is better when your active mode current outside the cpu is high. As with all things, which is best is going to depend entirely on your application.
  7. You need to know which one to use. How you figure this out is not always obvious. The quick and dirty way is to do ls -ltr /dev both with and without your desired device plugged in and look for differences.
  8. The goal is to sense whether a line is hot, not measure the current through a load.
  9. The app note I referenced discusses both resistive and capacitive supplies. Look for the "Advantages and Disadvantages" section under each.
  10. You might also want to check out this app note from Microchip on transformer-less power supplies: ww1.microchip.com/downloads/en/.../00954A.pdf You could use one of these to drive an opto-isolator if you want a steady-state signal.
  11. It is not uncommon for recent ATX power supplies to be capable of 30 amps or more on the 3V rail, and even older ones were capable of 15 amps. 15 - 30 amps through a short circuit will make for quite a bang, and if that short happens to be through silicon, well, I hope you are wearing safety glasses.
  12. If you don't add current limiting to a PC power supply you *will* regret it at the worst possible time. The simplest way to do this is to regulate the 5V rail down to your desired voltage with a linear regulator that does current limiting such as the LM1117.
  13. USB devices most commonly present themselves as serial devices, and since OSX is Unix, it uses the same serial interface that Unix has used for the past 30 years (or more.) Your Java VM and any Objective-C libraries are eventually going to call these these routines.
  14. At this point it is worth noting that the forward voltage drop of blue (and phosphor-colored LEDs driven by blue or UV elements) is typically close to that of the operating voltage of the msp430. When you factor in the voltage droop of loaded MSP430 pins, you'll get some some degree of current limiting even when connecting one of these LEDs without a resistor. But again, just because this works (and you may find other people doing it) doesn't mean you should do it unless you fully understand what is going on.
  15. What you are describing is the LaunchPad. All of the LaunchPads contain a proper programmer as well as a basic debugger and virtual serial port in a very small and cost-effective package.
  16. In the olden days -- long, long ago -- the final drive circuitry for many logic parts could source more current than it could sink. In most cases with modern parts this is no longer the case. You can always find specifications in the datasheet. If you cannot find them, you are looking in the wrong datasheet. Always be careful when only a single value is specified -- pay attention to what that number means! In some cases, that is the limit to what the chip can take without damage. In others, it is the limit to which it can maintain the proper output voltage levels. For some parts (
  17. http://forum.43oh.com/topic/2351-voltampwatt-meter/
  18. I'm not entirely sure if it will help, but here is how you do it in vanilla C: http://www.cmrr.umn.edu/~strupp/serial.html
  19. For those looking to do overall current measurement on the cheap, you can charge a capacitor to your working voltage, use it as your power source, and then time how long the circuit takes to drop 0.1 volts.
  20. Not necessarily. Many low power apps spend almost all of their time in deep sleep with all external circuitry shut down. They only wake on command (or on an interval timer) for a very brief period of time. Operational current during this time can make the difference between a battery that lasts only one year or one that lasts five.
  21. If you son is comfortable with CCS, let him use it. Some children raised on computers are not intimidated by a screen full of buttons and menus. However, be aware that CCS and Energia differ in more than their interface. Energia uses a library that abstracts away much of the details of the hardware, making it much easier to use for beginners. But again, so long as your son isn't getting frustrated, let him stay with CCS. Learning how to program microcontrollers natively (that is, without an abstraction layer like Energia/Arduino) is not intrinsically difficult, but sadly there is ve
  22. Here is another thread to read: http://forum.43oh.com/topic/1913-frequency-counter-using-launchpad-nokia-5110-lcd/ And don't miss this: http://www.leapsecond.com/pdf/an200.pdf
  23. Check out libfixmath: https://code.google.com/p/libfixmath/
  24. Doing so saves you the cycles required to initialie the variables. The ULP is pretty bogus, IMO. It will help you shave tiny fractions here and there, but it is completely obvlivious to fundamentally bad design.
  25. One thing to remember when using interrupts on pushbuttons is debouncing. If you do not disable interrupts for the duration of the bounce period you will get hit with a chain of interrupts that will almost certainly cause problems.
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