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Thread: Custom Teensy power on

  1. #1
    Senior Member onehorse's Avatar
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    Custom Teensy power on

    I just put together my first custom Teensy 3.1 using the reference schematic here, verified that the boost converter is producing 3.24 V, verified that the reset signal on the K20 is being reset at 20 kHz, verified that when I press the program pin the reset signal goes to zero, but the K20 doesn't seem to get programmed by the Mini54TAN and I'm not seeing anything on the MINI54TAN SWD lines after the press (maybe I saw something once). And sometimes the K20 reset signal doesn't go low even when I press the program button. And of course my laptop doesn't see it. Does this sound like one or more cold solder joints? I had a bit of trouble getting every single last K20 pin to make a good solder connection. I'll assemble another one just to see if it behaves the same way. Any advice from the experienced?

    Second one doesn't work either. I notice that pin P2.5 and P1.4 of the Mini4554TAN are tied to GND in Paul's schematic but on the one I used from the link above they are floating. Could this be causing a problem>
    Last edited by onehorse; 12-13-2015 at 04:40 AM.

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    Hi there - I just did my own board as well - one crucial step is to download a first program from the Teensy Loader - did you do that? Secondly, if the processor is running normally but not programmed you should see it periodically pulse the RESET line - is that happening?

  3. #3
    Senior Member onehorse's Avatar
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    I am just putting together my first revision with test pads to better diagnose the Teensy board behavior. How do you download a first program from the Teensy loader? In the usual way? I tried but the Teensy was not recognized by the pc in the first attempt.

    Built first revision. Verified I am seeing 50 microsecond reset pulses from the MINI54TAN, verified the reset goes low when I press the program button,the reset line goes high for a moment but then goes back to the 20 kHz pulses. I can see the MINI54TAN send clock and program pulses to the K20 upon pressing the reset button, but I am not seeing the device on the pc and I cannot measure anything on the crystal lines or D+/D-. I suspect I am not starting the crystal.

    I guess I'll ask again since I haven't gotten a definitive answer, but do I need 12 pF load capacitors on my 8 pF crystal or can I rely on the internal load capacitance of the K20?
    Last edited by onehorse; 12-27-2015 at 12:05 AM.

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    Senior Member Constantin's Avatar
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    Quote Originally Posted by onehorse View Post
    I guess I'll ask again since I haven't gotten a definitive answer, but do I need 12 pF load capacitors on my 8 pF crystal or can I rely on the internal load capacitance of the K20?
    You do not need the external caps. The MK20 takes care of that internally. Are you using the NX series crystal that Paul also seems to use on the MK20? If so, are you grounding the two GND pads on the thing? That was the most recent issue with getting a MK20 going.

    As for the first program. I'd try compiling and uploading blink() because it verifies everything that needs to be verified.

    As for the floating pins, I'd follow Pauls' schematic. If it's supposed to be grounded, then rub off some soldermask and blob the pin or run some 30AWG wire.
    Last edited by Constantin; 12-27-2015 at 12:49 PM.

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    Senior Member onehorse's Avatar
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    The latest attempt has the correct MINI54TAN schematic, and the MINITAN seems to be behaving correctly. I connected the crystal caps between the GND pins and board GND by mistake so on the latest attempt I just used 0 Ohm jumpers. Somehow even though the MINITAN sends the initial program to the MK20, it doesn't start the crystal going (I guess) and the reset doesn't stay high, nothing on the USB data lines and the pc sees no new hardware.

    I am using an Epson FA20H 16 MHz crystal with 10 ppm tolerance. It's the same one I use successfully on the nRF51822 and nRF24L01+.

    It could be bum K20s, which I bought cheap from China, or some other trace error.

    I redesigned the board to use the newer boot loader, so I'll give that one a try. If that fails, I'll try a simpler circuit/board design. I'll get it to work eventually!
    Last edited by onehorse; 12-27-2015 at 06:49 AM.

  6. #6
    Senior Member Constantin's Avatar
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    IIRC, sensing whether the crystal is running or not appears difficult as probing that circuit usually kills the signal. I'd take a oscilloscope and compare the output @ the two crystal pins of a regular (i.e. known good) Teensy 3.x and compare that to your DIY.

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    Senior Member Constantin's Avatar
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    Also, I would not buy critical components from no-name sellers in China or anywhere else, for that matter.

    Consider the value of your time... Pay the premium and use Digikey, Mouser, or some other reputable source that will sell you genuine articles (not rejects, scavenged, or otherwise questionable components) that are packaged in static free bags with dessicant pouches, etc.. to ensure that the only issues are associated with your board, not the source of your components.

  8. #8
    Senior Member onehorse's Avatar
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    I would not buy critical components from no-name sellers in China
    Well, I think I finally got bit on this one.

    The K20 chips have a 2012 date and were sent just sitting in a plastic tray in a baggie. But I saved a couple of dollars per chip!

    I have had very good luck buying MPU9250, BMX055, BMP280 and BME280 MEMs sensors by the hundreds from no-name vendors in China (actually, there are a few Chinese vendors I use regularly) and have had no more than one or two chips fail to function as expected. The cost savings can be tremendous; I pay ~$3 each for the MPU9250 delivered but would have to pay ~$6 to buy from CDIWeb.com or Digikey, etc.

    On the other hand, a 100 unit build at a Chinese fab just had to replace all of the BMP280 sensors since none of them seemed to work! Even the Chinese have trouble occasionally finding reliable Chinese vendors!

    But in this particular case, and for prototyping in general, I wholeheartedly agree, by using quality components an unproven design can be best diagnosed. I think (and hope) this is what is going on with my efforts at making a custom Teensy board. I will know in a week or so; I just got my brand new, packed-with-desiccant, in-a-mylar-anti-static-bag K20s from Mouser. The new boards will be arriving from OSH Park presently.

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    Quote Originally Posted by onehorse View Post
    I have had very good luck buying MPU9250, BMX055, BMP280 and BME280 MEMs sensors by the hundreds from no-name vendors in China (actually, there are a few Chinese vendors I use regularly) and have had no more than one or two chips fail to function as expected.
    I am astounded that you've had success doing this & not getting inoperable fakes; which vendors? I'd like to try it myself.

  10. #10
    Senior Member onehorse's Avatar
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    I use www.aliexpress and buy from nearly the lowest per unit price vendor after checking the number of diamonds (some kind of rating) and any feedback (rarely any). It's hit or miss, but when I find that an order of five or ten of something produces five or ten real units that work, I go back for more. I have bought sensors, battery chargers, motor drivers by the hundreds with success. But YMMV. Here are some recent purchases:

    http://www.aliexpress.com/item/BMP28...464152465.html

    http://www.aliexpress.com/item/50PCS...548514208.html

    http://www.aliexpress.com/item/MPU92...451318400_6151

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    I'm also using some of my components from china, maybe some of them were recycled IC or whatever,
    most of them worked well.

    I met problems on my customed board,
    so from mentioned above, is the crystall's ground pin supposed to be floating , or connected to ground?
    thanks

  12. #12
    Senior Member Constantin's Avatar
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    Quote Originally Posted by Po Ting View Post
    I'm also using some of my components from china, maybe some of them were recycled IC or whatever,
    most of them worked well.

    I met problems on my customed board,
    so from mentioned above, is the crystall's ground pin supposed to be floating , or connected to ground?
    thanks
    Connected to GND

  13. #13
    Senior Member onehorse's Avatar
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    Finally got my new boards and assembled one with the fresh K20's I bought from Mouser and it worked the first time. I think the trouble I was having before was due to the bum chips. Lesson learned!

    Here is the newborn; I am so happy!

    Click image for larger version. 

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  14. #14
    Senior Member+ defragster's Avatar
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    Congratulations! All while working on your cool ESP8266 variants too!

  15. #15
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    @onehorse :Congrads!
    if thats my problem too, then I'm expecting to my chips working this time,
    too sad for bum chips

  16. #16
    Senior Member onehorse's Avatar
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    Thanks guys.

    The second one I put together tonight also worked great. I will add frame and brushed DC motors and try to fly one on Monday!

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