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jpnorair

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Everything posted by jpnorair

  1. @@basil4j Here's the deal: Nintendo ran on a square wave circuit, a triangle wave circuit, a video IC, and a piece-of-junk ~17MHz 6502. Yet clever programmers were able to extract amazing performance out of it. In your situation, you can chose to be a clever programmer or a clever architect. With MSP it may get tricky at the late part of your project, and with ARM you have the learning curve at the beginning. So you are going to have to deal with a challenge either way. But it's a million miles away from being an insurmountable challenge.
  2. I am an old person. What is the advantage of using javascript for this sort of thing?
  3. Relatively slow, but it sleeps at very low power and there's of course the FRAM. You don't really have a lot of math to do, and certainly the trig can be table driven, so it should be OK. That said, I bet you'll find that a low-power CM3 actually uses less power than the MSP does for this application, because there isn't much sleeping.
  4. jpnorair

    Mailbag

    We just received a box full of pre-release HayTags. Here's one.
  5. <Keanu>Whoa.</Keanu> Are they stuffing also?
  6. If you're going to go from Propeller to MSP430, then I recommend using the 5-series. There's a Launchpad 5529, which is overkill, but it's cheap and easy. Alternatively, there are lots and lots of Cortex M parts now. ARM Cortex M is like the Borg -- ultimately, resistance is futile.
  7. The question you really need to ask yourself is UDP, TCP, or if you are adventurous, SCTP. At the application layer, the discussion is more about what kind of API you want moreso than what kind of networking features you want. In any case, MQTT is used for some things where REST is too much protocol overhead, especially push notifications, but generally both MQTT and HTTP are implemented above TCP, so the limitations are the same. That is, with TCP you get generally get stuck needing a centralized hub, and there's no way to broadcast. If you need to broadcast, you need to use a UDP or S
  8. That's the thing. I'm more compelled to use something like Linino for any sort of multi-purpose, Ethernet-connected device. If the goal is to use RJ-45 interconnect, then power-budget is not a practical issue the way it might be with wireless or USB interconnect, and Linino gets me a platform that is much easier for IT-types to use and deploy. Now, if I want to build a USB-stick that uses Ethernet-over-USB, then this platform is more sensible.
  9. I'm just ranting and raving here, but 7 years ago there were boards like this (of course, not anywhere close to US$20) running ARM7 and ARM9. Atmel had a bunch of nice SAM7 and SAM9 parts. Anyway, the rant is not about the board. It looks pretty great. The rant is that the "IoT" marketing is crazy to me. It's a new word for something that isn't new in this case. For me, an IoT board needs to be wireless. The specific type of wireless is less important, but it must be there in some way! If only they had plopped-on a CC1200! (CC3000 might be too $$$)
  10. The RTL schematic you've hashed-out above is a classic solution, although it's possible to get really small CMOS drivers & level shifters these days, and that may be a better option depending on your needs. If I were in your place, I would probably first look at a CMOS driver. But, RTL is a good thing to learn in any case. Secondly, depending on your application it is sometimes better to use PFM vs PWM. For PFM you will need a slightly more complicated analog circuit and the response will be slower, but the noise will be less, and if you want a learning experience it might be worth
  11. VNAs are really only good for two things: S11 and S21 (well, and S12, but that seems pedantic). Mostly I use S11 on antennas, but I also use S21 for analog circuit analysis. Another use I've found is as a carrier signal source. When testing antennas, I can go to the spectrum of interest and turn the sweep down really slow, and then capture the transferred energy using a spectrum analyzer on the other side of the room (connected to reference antenna). Always remember to choke the probes!
  12. jpnorair

    Mailbag

    I second the "take pics." As for removing it, all you need is a sharp knife, good tweezers, antiseptic, and some super glue (long story, and nothing to do with RFID). On this note, I also recommend installing it into a part of your body easily accessible to your dominant hand. Embedded engineers are accustomed to soldering tiny components. Surgery is a walk in the park.
  13. jpnorair

    Mailbag

    It also looks sort-of like an RF board I've been working-on, at least in dimensions. I evaluated dozens of variations of planar antennas through OSHPark as well, so Laen must think we are in it together . Where did you get the stencil? How much?
  14. You could probably fit this onto a PLCC-44 chiclet board -- i.e. a PCB that fits inside a PLCC-44 socket -- if you really wanted to.
  15. OK then, with that simple telemetry application, it gives you more freedom to make tradeoffs. With compact antennas, it is possible to trade-off bandwidth, efficiency, and size. There is something called "Chu Limit" for antenna size, which you can look-up if you are curious. The ISM R1 433 and 866 bands are quite narrow, so in these bands it is OK to have an antenna without large bandwidth. For your base station, mount it high if you can. If you feel confident building and matching a 5/8 wavelength monopole, that is a great choice for the base station. If not, then a standard 1/4 w
  16. What kind of data rate do you need? If you are in North America, 915 MHz is probably the best choice for this, because the transmitter power can be extremely high (even up to 1W), and it is allowed to use DSSS. In south america, some countries have this band also, but others do not. In the rest of the world, there is nothing like it. Your best bet in the rest of the world is to use 433 MHz at 10mW, which is quite alright for sending 300m at relatively low data rates. Building a 433 MHz compact antenna can be difficult, but certainly not impossible. Plus, in a couple months you can jus
  17. This is not strictly an embedded system or test equipment deal, but perhaps some folks here might want a truly bad-ass CAD package. Back in the day, I used to do a lot of 2D and 3D CAD. FormZ is probably the most capable modeler I've ever used for engineering purposes. It is also rather easy to use and has a friendly UI. Today I certainly use FormZ to design complex copper patterns beyond the ability of the drawing tools in Eagle, DipTrace, or even Altium, Allegro, etc. FormZ also has bulletproof file conversion for tons of 2D and 3D CAD formats. It is still $700, but if you think you
  18. Oops, that's it. CM3. But it's a low-power CM3 similar in spec to STM32L, which (I would say) competes with MSP430F5.
  19. TI does offer great support, but support only goes so far. If you want to build a device that uses ARM CM, and you want to build it for low cost, TI probably isn't the answer. Re the MSP430, I'm surprised TI hasn't announced a roadmap with MSP migrating to ARM CM. It will either happen, or MSP will just fade away. TI is already releasing CC SoCs with CM0+, so it is clear which direction things are heading.
  20. It should be a piece-of-cake to port Maple (leaflabs.com) to the F103RB version. Maple is an Arduino/Wiring environment that has been around longer than Energia has. If you are a hobbyist, maybe the Tiva-C kit has more features. But as far as being a dev kit or evaluation kit for a product you want to build on ARM CM, the STM32's are priced really well. Tiva is much more expensive. Regarding ethernet, I'm kind of surprised that there hasn't been more action towards Ethernet-over-USB on these USB-enabled ARM CM's. Really, what you want to do is telnet into it. Whether it is over USB
  21. Are you simply feeding the antenna into the ADC? This may not work so well without a matched-impedance LNA between them. Most antennas are designed to 50 Ohm. In any case, later in the year I would love to try this. Send me email or just post here if you need advice on the RF and antenna circuits. Moreover, I would love to see if I could heterodyne the Loran-C band into 434 MHz, for local rangefinding, which should also simplify the receiver from an ADC implementation into a zero-crossing implementation. Finally, if you need better crystal precision, the best way is to use a TCXO.
  22. First off, the CC430 spectrum analyzer is fun, but a DTV-B dongle is a lot cheaper and a lot better. You might want to see if there's some SDR dongle that works with GNU radio and that sort of thing. There should be an SDR somewhere that merely plops a downconverter onto a DTV front end, I would think. However, VSWR, return loss (same thing), insertion loss, etc, are things for which you need a different tool. This is a Network Analyzer. There is no short-cut to a network analyzer that I know of, but maybe it would be possible to blast noise at network and then just do the FFT thing to
  23. Sooo... I have these dev kits called "Jupiter" that I make. You can notice that: (a) they don't use MSP430, (b ) they are half-size Arduino Uno form, and (c ) there is a 30 pin edge connector. It is called "Jupiter" because the plan from the beginning was to have a series of female adapter boards that attach to the 30 pin edge connector, which fill-out the rest of the Uno form factor while providing some additional functionality. So far I have planned 3 adapter boards. One of these would be a WiFi + Ethernet board. It would be fairly easy to copy work that has been done already, such as Y
  24. There are many ways to get a good result, but components cannot be inside the board, and vias add reactances, so we need to find ways to put the traces on the outer layers. Fortunately, there are ways! ST has a nice app note, I think it covers pretty much everything. http://www.st.com/st-web-ui/static/active/en/resource/technical/document/application_note/DM00065838.pdf The main thing you need to think about is the fact that the traces on the board can act as antennas if you do not design properly. They can also cause impedance mismatch, causing less power to go to your antenna if yo
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