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Thread: Help creating a custom PCB based on Teensy LC

  1. #1
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    Help creating a custom PCB based on Teensy LC

    I hope you don't mind me reaching out on the forum. I have a commercial product which I use the Teensy LC board for but I am finding it difficult to mount the board flat because I use the USB pads to mount to another PCB and I have a USB cable going over the top of the Teensy, so need it as low and flat as possible.

    Because of this I would like to build a custom PCB rather than combining the 2. That's the plan but I have no ability when it comes to electronics. I can bolt things together and design my PCB's in Eagle but its simply tracks connecting the Teensy to a couple of plugs.

    Click image for larger version. 

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    All I am doing is connecting an 8 Pin JCT PH plug and a 6 PIN Wire header for the USB as you can see in the attachment.

    Would anyone be willing to help me design a board that has the Teensy LC components built in? I am happy to pay as this is a commercial product that I sell.

    I should add that my code is open source and can be downloaded by anyone... My product just combines various parts that you can buy off the shelf to make it easier for people to use. I would place the PCB design openly in the blog section and with the code.

    Kind regards
    Simon Maltby
    Sim Racing Machines UK

  2. #2
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    This is what the product currently looks like. I have a couple of slightly different versions.

  3. #3
    Senior Member crees's Avatar
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    I could possibly help if you don’t find someone. I have made several custom boards with the teensy bootloader and chip. I’m in the the middle of a project at the moment but later next month i should be more free to take on another project. PM if you haven’t found anyone

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    Thank you... no one else has responded.
    It really should be fairly simple. I am trying to do it myself and will put the design up for, hopefully, someone to validate.

    I get that I need the crystal and think I need a capacitor to the 3.3v output.... what I cannot work out at all is if I need any resistors or diodes?

  5. #5
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    Ok I've got as far as I can with the basic design.
    Click image for larger version. 

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    Questions.
    1. Are my connections correct?
    2. Where do I connect USB D- and D+?
    3. Where do I connect the Crystal?
    4. There is confusion in the list of connections regarding PTA3... it says pin 20 and pin 3
    5. How do I connect a program switch in relation to PTB2

    Sorry for all the questions.
    The JST PH plug has the pins that I connect to the Teensy LC to help.

    Thanks
    Simon

  6. #6
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by simonmaltby View Post
    2. Where do I connect USB D- and D+?
    3. Where do I connect the Crystal?
    Use the published schematic as a guide.

    https://www.pjrc.com/teensy/schematic.html

    2 - connect 33 ohm resistors
    3 - connect the crystal to only the 2 pins on the MKL26 chip


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    Thank you Paul... I had not found that diagram

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    [ATTACH=CONFIG]17980[/ATTACH

    Could you please explain what these 2 symbols mean?
    Are the capacitors on the VDD and VUSB nets needed?

    Thank you
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Quote Originally Posted by simonmaltby View Post
    [ATTACH=CONFIG]17980[/ATTACH

    Could you please explain what these 2 symbols mean?
    Are the capacitors on the VDD and VUSB nets needed?

    Thank you
    Paul will correct me if i am wrong - the left arrow is a fuse, the right arrow is a pad that can be cut and resoldered again if necessary

    some neat products you have - do you build motion sims as well as wheels ?

  10. #10
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    Quote Originally Posted by Gadget999 View Post
    Paul will correct me if i am wrong - the left arrow is a fuse, the right arrow is a pad that can be cut and resoldered again if necessary

    some neat products you have - do you build motion sims as well as wheels ?
    Thank you... that makes sense.
    Just need to know if I need all the caps between VDD / VUSB and ground?

    l don't do motion myself, but have a motion system on my own rig which is excellent.

  11. #11
    Senior Member crees's Avatar
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    Generally you donít want to omit caps feeding the MCU. They are essential in filtering out unwanted frequency and ripple disturbances etc. Omitting them may contribute to the teensy acting erratically. You also have more caps coming off the mcu 3.3v output that also cleans up that power rail to the bootloader chip. All necessary for Stable performance.

  12. #12
    Senior Member PaulStoffregen's Avatar
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    Each capacitor needs to be physically close to a pair of power pins. The wires need to be short and have minimal loop area for the capacitors to be effective.

    If you put them all together somewhere on your PCB, you might as well only use 1.

  13. #13
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    Do you mean a single bigger value Cap? So where we have 3 x 0.1uf and a 2.2uf can I use 1 x 2.2uf or 1 x 2.5uf or even 1 x 3uf?

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