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Thread: Teensy 4.1 solder pads for USB ...

  1. #1
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    Teensy 4.1 solder pads for USB ...

    Good morning all.

    I have been using Teensy 3.2 micro-controllers for a project very successfully. For various reasons, I have to solder the PC-USB cable to the reverse of the board (mainly, no room for a USB plug), and I have done that successfully several times with no issues, as the pads are clearly identified.

    However, I have now moved the project to the Teensy 4.1, and it is working. However, I need to sort out the solder points for the four PC-USB wires. I note that D+ and D- are clearly identified on the new 4.1 board, but with the 3.2, I also connect the PC-USB-Red to the large upper pad (USB+) and PC-USB-Black to the large lower pad (GND).

    Could someone kindly tell me where on the T4.1 board should I connect the PC-USB-Red and the PC-USB-Black wires from the PC-USB cable? I note that there are 4 nearby (smaller) plated through holes and wondered whether I should use any of those for the PC-USB-Red and the PC-USB-Black wires? I don't really wish to play Russian Roulette with those two connections, because it looks to me as though all of them actually connect to the micro-USB socket case - if so I'd be shorting the PC-USB+ and GND!

    Any advice will be gratefully received!

    KASpencer

  2. #2
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    I know, the sequence of 5 USB pins on the side are for 2nd USB that one typically uses for USH-Host, but can be programmed as USB device.
    But if you, like me, wanted to use USB not only for Serial but also for programming, you must use the two tiny dots below the USB connector.
    I wished Paul had made the two dots larger, but, I guess, they were originally thought for pogo pins.
    The USB GNG (black line) goes to Teensy GND.

  3. #3
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    Thanks alot for that, WMXZ!

    I spotted the tiny circular pads for D+ and D-, and they are fine as they are labelled.
    And thanks for pointing out the GND connection for the PC-USB-Black wire.

    Looking closely at the board, I think that the PC-USB-Red wire will go to the pin, unlabelled on the 4.1, but labelled on the 3.2 as VUSB, with a larger solder pad adjacent to it?

    Thanks again if my assumption in my last line above is correct, than I have it - excellent.

    KASpencer

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by WMXZ View Post
    I wished Paul had made the two dots larger
    Lots of PCB routing guidelines for USB say not to have any routing stubs like these pads. For Teensy 4.0 I didn't route any stub traces. On Teensy 4.1 I risked these 2 small pads. Indeed the main idea was for pogo pins so we can verify the connectivity during the much more detailed bed-of-nails test.

    Teensy 4 USB runs at 480 Mbit speed, so the routing requirements are much more important than the 12 Mbit speed on Teensy 2 & 3. How large do you believe those pads and routing stubs could be?

  5. #5
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    Quote Originally Posted by PaulStoffregen View Post
    Teensy 4 USB runs at 480 Mbit speed, so the routing requirements are much more important than the 12 Mbit speed on Teensy 2 & 3. How large do you believe those pads and routing stubs could be?
    I appreciate the risk and routing. But if the two pads were small ovals (or rectangles) twice the size of the actual dots, soldering would be easier, safer?
    Anyhow, I succeeded to solder two short wires from T4.1 to custom base board before soldering teensy to header.
    As with OP, I cannot afford space for a USB connector, but need possibility to download firmware while teensy is in small housing and speed is not as critical, but welcome.

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