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Thread: Please help a lugnut...

  1. #1
    Senior Member Constantin's Avatar
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    Please help a lugnut...

    This is just depressing... last night and today I spent several hours assembling a number of custom Teensy's... and every single one is not responding to the loader.

    I am afraid that I must be doing something fundamentally wrong with wiring connections, so I wonder if someone could be kind enough to compare my schematics to Pauls, hosted here.
    Click image for larger version. 

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    For anyone interested in the relevant board section, it is below:
    Click image for larger version. 

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    OK, off to pull out the logic analyzer, oscilloscope, and so on. (sigh)
    Last edited by Constantin; 06-02-2016 at 01:06 AM.

  2. #2
    Senior Member onehorse's Avatar
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    I always ask this question, but isn't D+ and D- switched on your USB connector?

  3. #3
    Senior Member Constantin's Avatar
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    Hi Onehorse - They are switched re: the convention (if ordering per the pin number) but the actual pin connections are right. I've fixed the symbol nevertheless. The less confusion, the better.

    Did some more review re: the schematic and found a real head slapper. The PTA3 and PTA0 signal lines (on the MK20) were swapped. Not sure if I can even attempt to solder this with wires. Very angry with myself.

    All bootloading designs now feature two lines crossing over each other. Argh.

    Thanks for your help!

    I think I need a beer now.
    Last edited by Constantin; 06-02-2016 at 01:58 AM.

  4. #4
    Senior Member Constantin's Avatar
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    It's ALIVE!!!!

    Now I need to thank whoever clued me into the existing of wire-wrapping wire. Used a sharp scapel to dig up the lines, then used WW wire to fix the switcheroo.... double blinkie going on.

    Well, that's going to be tedious... but it'll save my employer several hundred bucks, so.... where is that beer again?

  5. #5
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    30 gauge!
    Not teflon insulation - requires special razor blade stripper

  6. #6
    Senior Member onehorse's Avatar
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    Glad you fixed it Constantin. One more step to becoming an expert!

  7. #7
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    Quote Originally Posted by onehorse View Post
    Glad you fixed it Constantin. One more step to becoming an expert!
    ex·pert

    ˈekˌspurt

    noun

    1. Past tense of a drip

  8. #8
    Member tcottle's Avatar
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    Quote Originally Posted by stevech View Post
    30 gauge!
    Not teflon insulation - requires special razor blade stripper
    You want to keep a cheap wire wrap tool in your box of tricks. It has a friendly 30ga stripper

    http://www.ebay.com/itm/Wire-Wrap-St...0AAOSw7PBToanO

  9. #9
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    Quote Originally Posted by Constantin View Post
    For anyone interested in the relevant board section
    Thanks for sharing this, it's always interesting to see how other people approach the same layout challenge.

    For comparison, here is my minimum viable teensy layout:
    Click image for larger version. 

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  10. #10
    Senior Member Constantin's Avatar
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    Thank you Tcottle, Very neat, Macaba!

    FWIW, the wire-wrap approach worked - very tedious to get those wires to stick on their respective 0.5mm pins and yet not touch each other (they are adjacent on the bootloader chip). Here is a revised PCB...

    Click image for larger version. 

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    For now, I'll live with my solitary via over/under rather than add a jumper 0805 or 0603 for PTA3 to jump over the PTA0 signal line. Seems to work despite long wire-wrap lines, so doesn't seem that sensitive...

    Still wrestling however with transferring library files between the Mac and my Windows machine. Somehow the Unicode gets in the way, and I get null character warnings that make the Arduino IDE throw up. Copying and pasting the content of the file to Notepad followed by a local save doesn't seem to address the issue. Saving it in native Windows formats doesn't help. Weird!
    Last edited by Constantin; 06-02-2016 at 05:21 PM.

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