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Thread: Pins to bring out on a hypothetical larger Teensy4

  1. #26
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    very good idea - could even be extended to two break lines - like maybe dacs closest to cpu and 5v tolerance parts
    out on the end so that if you wanted dacs but didn't need 5v tolerance you use the break line furthest from the cpu
    and if you wanted neither you could use the break line closest to the cpu. i have no idea how practical that might be
    given number of copper layers in the board and layout restrictions.

  2. #27
    Senior Member+ mjs513's Avatar
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    Been playing with servos for a couple of projects and I know that this might be a sin but it would be nice if a few of the PWM pins could be 5v tolerant - know they all won't be but a few would be nice.

  3. #28
    Another idea... why not this?:

    Click image for larger version. 

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    I mean... why only 1 row on each side?

    Make it not longer... make it wider :-) Or make it longer + wider + cutable

    Then anyone can place pin headers where they want them.
    And then we never have a pinout problem!

    Be creative!

  4. #29
    Having only one row on each side means you can plug into a breadboard. Two rows you can't.

  5. #30
    Senior Member+ KurtE's Avatar
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    My $.02

    Allowing the board to be Cut or snapped:

    Having it, such that it can be cut or the like could create lots of other issues. Like, can you route this board in such a way that only those signals run into that area of the board.

    Plus what is the likelihood that cutting/breaking the board could create signal breaks or short or slight changes in signals... So suppose Paul did that, how many boards should we try to snap off the end would we need to do, in order to have a confidence level, that it did not completely screw things up...

    Multiple Rows:
    As for two rows, as mentioned you can not populate both rows and have it work on breadboard. However you can not do that today with T3.2 with bottom pads either. So as long as one understands the limitations...

    My Preferences:
    Make the layout of it as compatible with the T3.5/6, especially for all through hole connections, including the USB. That way in many cases one might be able to swap this new chip into boards created for the 3.6... Sort of like the FRDM castellated board converts the current T4 into that size package. If one or two DAC pins are added, it would be great if they went to where the DAC is on T3.6...

    Edit: also if space is available, maybe pins that correspond to the position of A10 and A11 on T3.5/6.

    As for additional pins that might be added beyond what fits into top pins... I am torn.

    One obvious choice is to see if we could add SMT pins on the bottom that align with one of the T3.6. Might in some cases be subsets, like if issue of getting the full 2x5 on end and a 2x4 works...

    Other option is to add additional Rows or columns of pins. But if for example if this changes the dimensions to be bigger than T3.6, this could easily cause it to not be a drop in replacement, as there may not be space on a current board.

    @Paul - But my strongest preference, is that it is a simple enhancement of the current T4, that does not require too much of your development time and testing time, such that you can start having the fun to figure out that next board with two different cores...

    But again that is only my $.02
    Last edited by KurtE; 11-21-2019 at 02:38 AM.

  6. #31
    My .02

    Keep it simple. Make the T4 in T3.6 format. Have a uSD holder and bring D24 to D33 to the through holes.

  7. #32
    Quote Originally Posted by skpang View Post
    Having only one row on each side means you can plug into a breadboard. Two rows you can't.
    At this time with the new Teensy 4.0 you can not use many pins with a breadboard, because they are on the back side :-)

    Outer 2nd Row: Breadboard is not a big problem... use an adapter board for breadboards (outer row with headers upside), or no adapter with headers upside for the outer row, and a 2nd Teensy for PCBs

    I think it would be better to go new ways. Old ways are too limited. An option were 2 versions, new and old.

    The good thing with the 2 rows is... you never have to solder anything on the back (PCB friendly :-)

  8. #33
    Quote Originally Posted by PaulStoffregen View Post
    I started exploring how the extra space might be used. Here's a quick concept drawing, with the added parts highlighted.

    Attachment 17964

    Switching to the larger 12mm chip (necessary for escaping more signals with an affordable PCB) and adding a USB host stuff (highlighted yellow) and SD socket similar to Teensy 3.6 uses up nearly all the space. I guess that's not too surprising, since Teensy 3.6 has a 13mm chip and not much room left over.

    At first it seemed impossible to fit an ethernet PHY and a connector. The 4mm LAN8720 chip I've used before just can't fit, unless the connector is extremely small (and fragile). Then I discovered Texas Instruments has a relatively new PHY chip that squeezes the PHY into only 3mm, using a rather strange QFN package. That allows a 2mm pitch through-hole header for the ethernet signals.

    One downside to the ethernet PHY chips is about 1 to 2 mA current in their lowest possible power down modes. Of course we'll still support the power on/off feature which will also shut off all power to the PHY.

    Which signals to assign to pins 34-41 is still a wide open decision. AD_B1_04, AD_B1_05, AD_B1_12, AD_B1_13 seem like reasonable candidates. That would give 16 bits of a port (though how useful that really is with the GPIO supporting only 32 bit access is questionable) and would also give 16 signals for FlexIO3 (perhaps much more useful). But those 4 pins are sort of lackluster in peripheral features, which is the reason they weren't included in the Teensy 4.0 pinout.

    Signals B1_12 & B1_13 would give us access to the last serial port (UART5). Or EMC_23 & EMC_24 could as well, if those signals are used for a place to add a memory chip (which would be on the bottom side - pads similar to the bottom side of the audio shield, but FlexSPI so the memory chip gets mapped into the ARM address space).

    This is all very tentative. Now is the time for feedback!
    ...all my dreams become true.....ethernet....thumbs up!!!

    Thank you

    Torsten

  9. #34
    The reader should remain in the orientation that teensy 3.6 has, it is more practical for the insertion / removal of the microSD card

  10. #35
    Senior Member+ MichaelMeissner's Avatar
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    Paul, out of curiousity, have you settled on what pins you are bringing out, and the pinouts involved? Would you be bringing out the pins currently underneath the Teensy similar to the various breakout boards floating around, or would you be bringing out new pins? Would even more pins be underneath the Teensy?

    If you are bringing out the current solder pads, it would be helpful if we could get people to think about everybody moving to a common pinout. Right now, each of the 3 main breakout boards use a different order and layout to get to the extra pads. Each has various advantages and disadvantages, but it may be helpful to have a common layout.

  11. #36
    Senior Member+ KurtE's Avatar
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    @Paul - any updates?

    Some things I am very curious about, is how compatible will the T4.? be with the T3.6 layout?

    Example can I drop in one of these instead of a T4 and use the USB host pins? That is will the pins be in same alignment and positioning? Your earlier picture looked like they are different?

    Likewise what about other Through hole pins on T3.5/6 like A10, A11, I can imagine AREF is problematic.

    Bottom SMT pins? Any that might be in same locations like T3.5/6 like ones under SDCARD (43-50)? ...

  12. #37
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    My preference is that teensys be small and inexpensive. Make a long breakout board for people who want to use lots of pins on a breadboard and make add-on boards for SD card, WIFI, etc. Double rows with the inner pins being fine pitch is fine (and better than bottom pads).

  13. #38
    Senior Member+ KurtE's Avatar
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    @jonr - we have a T4 that is small and inexpensive. But Paul asked what pins we might want in a T3.6 form factor as per post #1
    I'm considering making another Teensy4 with the same 1062 chip we have on Teensy 4.0, but in the Teensy 3.6 form factor.
    Edit: I meant to mention, that I am not in full disagreement, just that thread is geared toward T3.6 form factor for T4... There is another thread talking about future Teensy....

    Also: personally I sort of liked a lot about the Edison just hated the support (lack their of) and some of the details.
    Last edited by KurtE; 12-03-2019 at 06:13 PM.

  14. #39
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by jonr View Post
    My preference is that teensys be small and inexpensive. Make a long breakout board for people who want to use lots of pins on a breadboard and make add-on boards for SD card, WIFI, etc. Double rows with the inner pins being fine pitch is fine (and better than bottom pads).
    Well not everybody is comfortable with connecting such things. Like everything, there are always trade offs to be made. The more you go to smaller connections it can reduce the number of potential buyers.

    For example, one of the original reasons I went with Teensy when Paul did the original kickstarter campaign 7 years ago was he offered the Teensy 3.0 with pins already soldered onto the board. While I can now solder through hole and occasionally SOIC connections, I do struggle with smaller connections. I'm sure there are other tinkerers that are similarly solder challenged.

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