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Thread: planning custom T3.6 - SD-Card (SDIO) and micro-USB on daughterboard?

  1. #1
    Junior Member
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    planning custom T3.6 - SD-Card (SDIO) and micro-USB on daughterboard?

    I am thinking about a custom T3.6 pcb for my product. There will be kind of a "headunit" with power supply, MCU, all needed interfacing hardware for connected sensors plus connectors for expansion modules . Further there will be a "frontend" (different frontends shall be possible, hence the modular approach) which visualizes information to the user. Headunit and frontend will be joined through a defined interface, maybe with a kind of pinheader-connector. It will be fully enclosed and only the front panel will be accessible in its final position. So I need the USB connector (for uploading code to the teensy, "software updates") and the SD Card (logging capabilities) at the front panel. To give the most flexibility in designing the front end both micro USB and micro SD card holder should be more or less free movable (in design stage, not in final product).

    (If you are interested I would like to share more details about the project itself later. A lot of breadboard prototyping and research has been done in the past 2 years. This community is awesome! Now it is time to move on to the first real prototype, what brings me to these current thoughts)

    My attempt: Put micro SD card holder and micro USB connector on a small daughter board and connect it with a jumper cable to the front end pcb which does nothing than route the signals to the interface-connector between frontend and headunit.

    Signal path would look like this: MCU -> traces on head unit pcb -> connector -> traces on front end pcb -> connector -> jumper cable (about 2" long) -> connector -> (short) traces on daughter pcb -> microUSB/microSD

    Jumper cable and sockets could be of this type:
    https://www.digikey.de/product-detai...148-ND/6194803
    https://www.digikey.de/product-detai...96-2-ND/926702

    I tried to find out as much as I could but maybe a more experienced user could give me an advice if this could work when designed properly or if I am on a total wrong way.
    Some documentation I already read:
    http://www.appfruits.com/2015/03/bui...custom-teensy/ (Phillip Schuster's experience, including USB related issues, often linked here as a reference for custom teensy attempts)
    http://cache.freescale.com/files/32b...ote/AN4215.pdf (an AN from NXP regarding pcb layout and design, not specifically for Kinetis MCU though)

  2. #2
    Senior Member brtaylor's Avatar
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    If it helps, here's a schematic of a fully pinned out Teensy 3.6 I've been working on. It has not yet been built, I'm working on some minor changes (hopefully the last revision, but the changes are feature additions to rc3, not revisions of errors) before sending off to fab:
    https://forum.pjrc.com/threads/53225...l=1#post189113

  3. #3
    Junior Member
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    Quote Originally Posted by brtaylor View Post
    If it helps, here's a schematic of a fully pinned out Teensy 3.6 I've been working on.
    I already saw that, great little thing!

    Although it does not really change my uncertainty related to my planned USB/SD signal path.

    So in case my first post did not describe my thoughts clearly:
    How are the chances that the described signal path in post #1 will lead to a working USB connector and SDIO-SD-Card holder on the front panel of my project? Any experience? Or further/other tips for placing USB and SD on a daughterboard because it is not possible to leave it on the same pcb as the micro controller? Thank you!

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